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The Wolf Within: The Astonishing Evolution of the Wolf into Man’s Best Friend

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William Collins

An imprint of HarperCollinsPublishers

1 London Bridge Street

London SE1 9GF

This eBook first published in Great Britain by William Collins in 2018

Text © Bryan Sykes 2018

Images © individual copyright holders

Cover images ©

Cover design by Jack Smyth

Bryan Sykes asserts the moral right to be identified as the author of this work

A catalogue record for this book is available from the British Library

All rights reserved under International and Pan-American Copyright Conventions. By payment of the required fees, you have been granted the non-exclusive, non-transferable right to access and read the text of this e-book on screen. No part of this text may be reproduced, transmitted, down-loaded, decompiled, reverse engineered, or stored in or introduced into any information storage and retrieval system, in any form or by any means, whether electronic or mechanical, now known or hereinafter invented, without the express written permission of HarperCollins.

Source ISBN: 9780008244415

Ebook Edition © November 2018 ISBN: 9780008244439

Version: 2018-10-01


To Sergio and Ulla

Illustration courtesy of Richard Sykes. This illustration depicts the tomb of Liliana Crociati de Szaszak in La Recoleta Cemetery, Buenos Aires, Argentina, which is known for its unusual neo-gothic design. Liliana was twenty-six years old when she was killed by an avalanche, and after his death several years later, her beloved dog, Sabú was added to her memorial. The text under the dog’s statue reads ‘Sabú, faithful friend of Liliana’.



Title Page




1 Lupa

2 Darwin’s Dilemma

3 I Met a Traveller from an Antique Land

4 On the Origin of Wolves

5 The Living Fossil

6 Let the Bones Speak

7 The Cave of Forgotten Dreams

8 Hunting with Wolves

9 Why Didn’t Shaun Ellis Get Eaten by Wolves?

10 Friend or Foe?

11 A Touch of Evil

12 The Basic Framework

13 We See the First Dogs

14 The Studbook ; of Dudley Coutts Marjoribanks

15 The Emergence of Modern Breeds

16 The Dog Genome

17 The Genetics of Pedigree Breeds

18 The Dance of Life

19 At the Heart of the Matter

20 In the Lab

21 The Scientist who Came in from the Cold

22 The Autumn Muster

23 The Girl who Talks with Dogs

24 Born Again: Cloning your Dog

25 Beyond the Reach of Reason




About the Author

About the Publisher


This book is about how wolves became dogs. A remarkable transition, it ranks as one of the most important yet least appreciated events in the long history of not one but two species. The wolf changed from a highly successful and independent carnivore into a highly successful yet completely dependent vassal with a bewildering array of different forms. The second species is, of course, ourselves.

All the evidence, which we will examine in this book, traces the start of the transition to about 40,000 years ago somewhere in Eastern Europe. Wolves had been living there and in all of the world’s circum-polar regions for millions of years. Our Homo sapiens ancestors were much more recent players, having newly arrived from Africa only a few tens of thousands of years ago. The scene was set for the encounter that changed the world.

The location was a steep-sided river gorge in the Carpathian Mountains in what is now Romania. There is abundant evidence of human occupation in the region from the time of the Neanderthals to the arrival of our Homo sapiens ancestors, and there is a good fossil record of the fauna to colour in the details.1

I hardly need add that the narrative of this meeting, found in chapter 1, is embellished with a generous helping of my own imagination, which I hesitated to include until I read Man Meets Dog by Konrad Lorenz, the Nobel Prize-winning biologist. He imagined a similar scene, though in a different location and with different players.2 I hope you find it evocative.

In 2009 the charismatic actor, Mickey Rourke, was nominated for an Academy Award and won a Golden Globe for his portrayal of over-the-hill fighter Randy ‘The Ram’ Robinson attempting to make a comeback in the film The Wrestler. The striking parallel between Rourke, the fading actor, and his character, so it’s said, was the reason behind the popularity of his nominations. In an interview with television host Barbara Walters to coincide with the film’s release, Rourke said of his own past:

I sort of self-destructed and everything came out about fourteen years ago or so … the wife had left, the career was over, the money was not an ounce. The dogs were there when no one else was there.

Asked by Walters if he had considered suicide, he responded:

Yeah, I didn’t want to be here, but I didn’t want to kill myself. I just wanted to push a button and disappear … I think I hadn’t left the house for four or five months, and I was sitting in the closet, sleeping in the closet for some reason. I was in a bad place, and I just remember I was thinking, ‘Oh, man, if I do this,’ [and] then I looked at my dog, Beau Jack, and he made a sound, like a little almost human sound. I don’t have kids. The dogs became everything to me. The dog was looking at me going, ‘Who’s going to take care of me?’

There are tens of thousands of stories like this. Of grown men, and women, lost in the world, who are saved by their dogs.

I am a scientist, a geneticist whose research has concentrated on the human past and our own evolution from upright ape to master of the universe, or so we like to think. It was a natural step for me to wonder at the equally remarkable parallel evolution of the dog that has been so closely tied to our own.

However, and it is best that I come clean right from the start, I am not a ‘dog person’. I lay the blame for this unfortunate disposition squarely on the muscled shoulders of the ‘Hound of the Baskervilles’, a huge Boxer living down the road from my childhood home in south-east London. From the age of seven, my route to school took me unavoidably past its house, and every day without fail the huge beast flew at the gate, ears flat back on its enormous head, snarling and gnashing its teeth. It was as if the Hell Hound itself had materialised in the London suburbs.

Many decades later, when it was suggested I write a book about the evolution of dogs, the memory of the hound came flooding back. ‘I can’t possibly,’ I answered feebly. But as the weeks passed and I began to do a little research I realised just how fascinating a subject it was and how extraordinary is the everyday sight of a person walking his or her dog. Here was a highly evolved primate and a savage carnivore, whose ancestors were once mortal enemies, living side by side as if it were the most natural thing in the world. My re-education has only gone so far, so please, dear reader, don’t expect childhood recollections of playful puppies racing across sunlit beaches or heart-wrenching accounts of how, had it not been for little Bella, I would have been unable to get over the loss of my favourite aunt. My starting point does at least allow me to be objective, even though I feel a little uneasy in being the only author of a dog book that I have come across who is not hopelessly in love with them.

The Wolf Within is primarily a book about the evolution of dogs and the forces that drove this astonishing transformation from a fierce and wild carnivore to the huge range of comparatively docile animals that is the domesticated dog. It is also about the other side of the equation, how it was that our own species Homo sapiens, an equally aggressive carnivore, formed such a special relationship with what, on the face of it, is a most unlikely ally. The Wolf Within contends that this is more than just a story of the subjugation of one species by another but a shining example of the co-evolution of two species to each other’s mutual benefit. Indeed, I conclude that this co-evolution was one of the vital steps in helping Homo sapiens gain the upper hand in the competition with other human species, such as Neanderthals, and to expand in numbers from relative obscurity towards the overwhelming numerical superiority and influence that we enjoy today.

The scientific substance of the book draws on the rich detail of the genomes of both dog and human that has accumulated over the past two decades. Thanks to these advances we are able to make out clear patterns in the distant origins of both species, resolving questions that have puzzled scientists for over two centuries. I also explore the history and practice of breeding and its influence on the health and the welfare of pedigree dogs. In parallel, I explore the breadth of this ‘special relationship’ between man and dog, including interviews with the owners of many different breeds, as well as the lengths some will go to immortalise their favourite pet through cloning.

As I mentioned a few pages back, we think nothing of seeing a dog and its owner walking together along the street, yet how did this everyday scene ever come about? We have long suspected that dogs descend from wolves. We know that the distant ancestors of today’s dogs formed close bonds with us a long time ago and there is a multitude of theories to account for our compatible social organisations. To a geneticist like myself, none of these is anywhere near enough to explain this most peculiar situation. In the harsh world of natural selection, only advantageous traits are conserved from one generation to the next.

Many owners who were interviewed for this book are fulsome in praise of their dog’s loyalty and companionship. That may well be true today, but it is grossly inadequate to explain the rise of the dog at a time in our evolution when we were living on the edge of starvation with no time for luxuries. No, there must have been a compelling evolutionary advantage in keeping a dog, not least to offset the extra demands of feeding it.

There is another question that requires an answer. Domestication (a wholly inaccurate phrase in my opinion but which will do for now) occurred at a time when all humans were both hunters and gatherers, but mainly hunters. In this respect their way of life had not changed a great deal for at least 200,000 years. There were plenty of wolves, hyenas, jackals and foxes about which could have formed the ancestral stock for the dog – and yet there is no evidence of ‘domestication’ until 50,000 years ago at the outside.

Many theories seek to explain what it was that propelled Homo sapiens from a scarce, medium-sized primate to the position of complete domination that we enjoy today. The ability to control fire, the evolution of language and the invention of agriculture are three prominent examples. I would add a fourth: the transformation of the wolf into the multi-purpose helpmate and companion that is the dog. We owe our survival to the dog. And they owe theirs to us.



At its narrowest point, the mighty Danube thunders through a narrow gorge, the Gate of Trajan,* cut by the river into the limestone bastions of the Carpathian Alps. Lupa, the she-wolf, stood at the edge of the gorge gazing down at the small figures making their way up the banks of the river a hundred metres below. They did not provoke in her any particular reaction. Humans had been using the river in this way for as long as she could remember. She and her pack did not have anything to do with the humans, but all the same she liked to keep an eye on them when they were in her territory. She knew the humans as brave hunters but they moved far too slowly to be very effective. They would eat anything that moved, including her fellow wolves if they could catch one. But that very rarely happened, and only if a wolf was sick or injured in some way. Earlier in the year, Lupa had watched the humans ambush and kill a young mammoth by driving it over the edge of the cliff, though this was unusual and most of the time they seemed barely able to scrape a living. For Lupa the main thing was to leave them alone and avoid unnecessary confrontations.

As the river mist lifted with the first rays of morning sun, Lupa could see the humans more clearly and, with her acute awareness of every detail of her surroundings, she sensed that they were a bit different from usual. They were a little taller, a little slimmer perhaps and moved a little more, how would she put it, a little more gracefully. Probably nothing in it, she thought to herself. Even so, I’ll keep a close eye on them. She turned away and trotted effortlessly back across the undulating grassland, dusted by an early frost, to join the rest of the pack. It was October and winter was well on the way. The river had begun to freeze over and the last of the reindeer had already moved down from the high plateau to their wintering grounds on the river estuary. It was time for Lupa and her pack to follow them, and next day she led them on the long trek downstream towards the Great Black Sea.

Along with Lupa and her mate of two seasons there were four young wolves in Lupa’s pack, two from this year’s litter and two from the year before. The pups, born in June, were just old enough to learn to hunt. Before that the pack was too small to be viable for long and it had been hard work getting enough food over the summer. As always, it was Lupa who organised the hunting. She decided what prey to target, even which animal to go for. She planned the chase to take advantage of any variation in the contours of the landscape and decided where to set any ambushes. The pack was completely dependent on her skill and leadership.

Meanwhile, the humans at the bottom of the gorge were not aware that they were being watched. They knew about wolves, of course. They occasionally came across one in the forests and were familiar with the eerie howling that kept pack members in touch with one another. But in general humans and wolves kept themselves to themselves. The new type of human, Homo sapiens, that Lupa had seen from her vantage point at the lip of the gorge had other things on their mind. The first of these was that the gorge was also home to Neanderthals. They were noticeably different in appearance, being much heavier set and therefore stronger, but at the same time were less agile. Neanderthals and moderns tolerated each other and, in fact, occasionally interbred. The biggest difference between the two human species was invisible. The Neanderthals were not as smart or inventive. They hadn’t changed their hunting methods or equipment for at least 200,000 years and showed little sign of ever doing so. The moderns on the other hand were always thinking of new ways of doing things. New designs of stone tools, of bows and arrows, the invention of the atlatl, or spear-thrower, and of all sorts of personal adornments. In time, these improvements would spell the end of the Neanderthals, and now there was one other innovation that was about to make an impact, a coalition between wolf and human, something the Neanderthals had never even contemplated.

The caves lining the Gate of Trajan were a favourite hibernation site for one of the most feared animals of the Upper Palaeolithic, the cave bear Ursus spelaeus, half as big again as the brown bear and with a voracious, omnivorous appetite for food which, from time to time, included humans, both Neanderthal and modern. Whereas Neanderthals abandoned the shelter of the caves as soon as they heard or smelled a bear nosing around, moderns had learned to leave the caves in the autumn and return a few weeks later when the bears were hibernating and kill them where they slept. This gave them vacant possession and enough meat to help them through the winter, should they wish to stay.

By early March the days were getting longer, although not appreciably warmer, and Lupa knew it was time to make a start for the high ground. The wolf pack had survived the winter by feeding off the herds of reindeer and wild horse which overwintered on the delta. But first there was the business of mating. Lupa was only receptive to the alpha male for five days every year. That was enough for her to get pregnant once again. She wanted to be sure to reach her traditional denning site in the hills in good time for the birth of her cubs. Very early one morning, with the frost decorating the dried stems of last year’s reeds, she led her pack away from the delta and headed west for the mountains.

In past seasons Lupa had arrived in the gorge ahead of the Neanderthals, who had also spent the winter on lower ground. This year she was surprised to see humans were already living around the gorge when she arrived with the other wolves. She made her way to her usual birthing den in a small cave hidden behind a patch of eroded scree high up on the side of the gorge. Ten days before the cubs were due, she settled down and waited for the births. For the period of her confinement the alpha male ran the pack. All the wolves brought food to Lupa which they left outside her den.

In due course Lupa gave birth to four blind cubs. One, the weakest, died almost immediately, but the other three developed quickly. Their eyes opened at two weeks and a week later they were beginning to feed on regurgitated meat. The following week, Lupa led her pups outside the den for the first time where they played under her supervision. The other wolves who had kept Lupa supplied with meat during her confinement now began to do their share of babysitting, giving Lupa a well-deserved break.

The first thing she did was to walk to her favourite lookout at the edge of the gorge to see what the humans were up to. She could see a small group paddling in the river, overturning stones and occasionally plunging their hands into the icy water to pull out a crayfish. This is something the Neanderthals never did. But the biggest surprise was still to come. On her way back to the den she saw not far away on the plateau a group of humans who appeared to be hunting. The Neanderthals never came up to the top of the gorge. These strange new humans were the same slimmer version she had seen the year before. Unsure what to make of them, she kept low to the ground out of sight behind a clump of dwarf willow.

Over the rest of the summer Lupa and her pack saw more and more of the humans up on the plateau.

She saw them ambush a wild horse they had deliberately separated from the herd. They had it cornered in a patch of marshy ground below a low bluff where it became trapped in the mud. Two of the humans – there were six in all – climbed the bluff with spears in hand. While the others spread their arms and shouted to confine the horse and prevent it from escaping, the two on the bluff raised their spears and hurled them into the struggling animal. It shuddered and dropped to the ground. All six humans crowded round the stricken beast and drove their spears deep into its chest. Once it was dead they took out stone knives, opened the abdomen and shared the liver between them. They then butchered the rest of the carcass and made their way back down the gorge. Not all their hunts were as successful as this, and more than once over the summer Lupa watched as the exhausted humans made their way home empty-handed.

The first flurries of winter snow fell on the high plateau in August and the reindeer were once again on the move to lower ground. The first snows heralded the best month’s hunting of the year for the wolves. Calves born in May were now almost fully grown but were inexperienced. The wolves knew which routes the animals would take across the undulating plateau and planned to intercept them in the pockets of soggy ground that lay in their path. Lupa led her pack, now nine strong, towards the ambush zone, many kilometres from their home near the top of the gorge. But something was troubling her. She stopped and sniffed the air. There it was again, the same scent she had first encountered at the site where the humans had killed and butchered the wild horse a few weeks earlier. Not only was Lupa’s olfactory sense very acute, she was also able to remember smells for months or even years. She knew very well the pungent scent of the Neanderthals, but this was certainly different, still strong but a little sweeter. Scent always being her primary sense, from now on she would recognise the new humans using her nose rather than her eyes. She scanned the horizon. She could not see any humans. She led her pack onwards.

Suddenly from a small clump of birch trees about twenty metres away an enormous bull aurochs charged out, heading straight for Lupa. These giant beasts, the ancestors of domestic cattle, had very short tempers and were extremely aggressive towards wolves. Lone bulls like this one were worst of all. Wolves knew better than to take on an enraged aurochs. It would take a much bigger pack than Lupa’s to subdue and kill such a giant. Before she had time to organise the rest of the pack, the beast was on her. She just managed to dodge the deadly horns on the first pass and moved backwards out of range. Seeing her in trouble, the first instinct of the rest of the pack was to protect its leader. The alpha male rushed into the attack, attempting to sink his long canine teeth into the beast’s huge neck. With a flick of the bull’s head the wolf was skewered on the aurochs’s left horn. Another flick and the bloodied body was flung to the ground. The other wolves went to attack, still desperate to protect their leader. The thrashing bull caught one of this year’s cubs full in the chest with its back leg then turned and trampled the winded and mewling animal and left it dying on the moss. Lupa herself now joined in, knowing full well that if she was killed or injured the pack was finished.

Just then, two humans appeared downwind over the crest of a low hill. They had been tracking the aurochs. They had heard the commotion and now they saw the reason for it. Standing well back, they took up position and hurled their spears at the snorting bull. The sharpened flint tips found their mark. One spear struck the animal in the flank while another buried itself deep in the beast’s chest, its razor-sharp edge severing the aorta. Blood spurted from the wound and the beast fell to its knees. It lay there quivering and within a few minutes it was dead.

The two humans advanced on the carcass, knives at the ready. They looked up, expecting the wolves to retreat, but instead they held their ground and lay watching in silence. The hunters opened up the animal and removed the steaming entrails. They cut slices from the warm liver and began to eat. When they had taken their fill but before they started to butcher the carcass, the younger of the two hesitated. He had seen how wolves ran down their prey, following them for many kilometres until the animals, weak from exhaustion, could fend them off no longer. Once they were sure the death throes no longer put them in danger of serious injury, the wolves would engulf the dying animal, ripping at the exposed abdomen and disembowelling it. An idea was beginning to form in the mind of the hunter.

Reaching into the ribcage of the fallen aurochs, the younger man ripped out its still-beating heart and tossed it towards the wolves, much to the dismay of his older companion. Still the wolves stayed where they were, their amber eyes fixed on the humans. After a full five minutes Lupa was the first to move, gingerly advancing towards the offered heart. The other wolves watched in silence. Lupa sniffed at the heart, then opened her wide jaws and sliced off a chunk of the left ventricle and began to eat it. Still the others did nothing. After a further five minutes, with an almost imperceptible movement of her ears Lupa sent a silent signal to the rest of her pack. They advanced and tore the rest of the heart to shreds.

When both wolves and humans had gorged themselves on the beast’s entrails they sat there looking at each other. Something passed between them. Was it a spirit message? Was it merely mutual admiration between hunters? Did either of them know what had just happened?

Over the years that followed, wolf and human grew closer together. The next spring, as lines of reindeer moved towards the skyline through purple meadows of crocus and gentian on their way to summer pastures, wolf and human followed to pick off the stragglers. Increasingly easy in each other’s company, they no longer kept their distance and it was not long before they began to cooperate in the hunt. Sensing a weakness among the reindeer, Lupa picked out the target animal in the herd. The pack trotted off in pursuit, with the humans following as best they could. As the isolated deer began to tire, the wolves formed a circle and held it at bay until the humans arrived to kill it with their spears. Because the wolves no longer needed to completely exhaust the animal in order to avoid injury, the chase was over more quickly. For their part, the humans had a static target for their spears. All shared the kill.

An Artist’s recreation of what a collaborative hunt, like Lupa’s, might have looked like. The wolves harry the aurochs, tiring it out, while the humans inflict the killing wounds from a safe distance. (© GraphicaArtis)

Wolf and human benefited from this collaborative hunting, and in the years that followed, long after Lupa had died, both groups learned to adapt and improve it. Wolves began to signal the presence of prey with a low-pitched howl. Humans understood the message and a hunting party set out to join them. Wolves and humans who hunted together prospered at the expense of those who did not. Their numbers increased and gradually the unstoppable current of natural selection spread this symbiosis across the rest of Europe. Eventually some wolves began to live with humans, intermittently at first, then permanently. Their numbers increased even more and, from this beginning, dogs began to evolve.

All this happened a very long time ago in the high and wild country above the Gate of Trajan. That was the start. We have yet to reach the end.

* Named after Roman Emperor Trajan (ruled 98–117 CE) and marking the northern boundary of the Empire.


Darwin’s Dilemma

It’s easy to pinpoint the moment when the collective view of how humans and all other animals and plants came to be changed abruptly. On 24 November 1859 the naturalist Charles Darwin published On the Origin of Species by Means of Natural Selection. The main contention of the book, that species were not fixed and could change over time, immediately challenged the predominant view of the Church that all of nature was deliberately and carefully designed by God himself. Humans were created by God in His image and, as such, occupied a special place above all other animals. The fact that all naturalists at the two predominant British universities, Oxford and Cambridge, were enrolled as Church of England clergymen as a condition of their employment only strengthened the grip that this ‘natural theology’ had on scientific opinion. To disagree was dangerously close to heresy.

At the heart of Darwin’s theory of natural selection was the concept that individuals within a species differed in their ability to survive and reproduce. Those that succeeded in what he referred to as ‘the struggle for survival’ passed on these qualities to their offspring, who were then better able to endure the struggle. Consequently, over time, new species evolved and others became extinct.

In many ways, Darwin was unlike any modern biologist. He knew nothing of genetics, the underlying principles of which lay undiscovered until well after his death in 1882. Nor did he work in a laboratory. Instead he relied on extensive correspondence with hundreds of his contemporaries throughout the world, persuading them to pass on information and sometimes to examine or collect specimens on his behalf. By these means, his accumulated wisdom and knowledge were immensely broad, which is what makes his writings such a joy to read. His theory of evolution took decades of development and refinement. Most of these were spent collecting a wide range of examples of his theory in action until he finally felt ready to publish.

The Expression of the Emotions in Man and Animals by Charles Darwin was published in 1872. Darwin’s book is among the most enduring contributions to nineteenth-century psychology and a testament to his fascination with the dog. The left illustration is captioned, ‘Half-bred Shepherd dog approaching another dog with hostile intentions’. The right, ‘The same caressing his master’. Both were drawn by A. May. (Science History Images/Alamy Stock Photo)

One important strand was Darwin’s observations of the creation of new forms by deliberate breeding, which he referred to as artificial selection. His favourite examples were the extravagant strains of domestic pigeon created by fanciers, the main reason being that he was pretty certain that they all descended from just one wild species, the rock dove Columba livia. As in all his work, Darwin was thorough and meticulous. He kept the main varieties of pigeon himself at home, and through his network of contacts collected as many skins as he was able from far and wide. He spent days in the collections at the British Museum and even enrolled in two London pigeon-fanciers’ clubs.

As well as pigeons, Darwin studied pigs, cattle, sheep, goats, horses and asses, domestic rabbits, chickens, turkeys and ducks, even goldfish, not to mention plants of many kinds. And, importantly for us, dogs. The first chapter of his accumulated thoughts on evolution through artificial selection, published in 1868 as The Variation of Animals and Plants under Domestication, is devoted entirely to dogs.

Right at the start Darwin sets out the principal question surrounding the origin of dogs.

The first and chief point of interest in this chapter is whether the numerous domesticated varieties of the dog have descended from a single wild species or from several. Some authors believe that all have descended from the wolf, or from the jackal or from an unknown and extinct species. Others again believe, and this of late has been the favourite tenet, that they have descended from several species extinct and recent, more or less commingled together.

Then he adds: ‘We shall probably never be able to ascertain their origin with certainty.’

Darwin’s questions on the origin of dogs remained unanswered for over 120 years until the new science of molecular genetics began to take an interest. In the chapters that follow we will explore what this new science has to say about the evolution of dogs and how, for once, Darwin has been proved wrong. We have been able to ascertain the origin of dogs with certainty.


I Met a Traveller from an Antique Land

This is not the first time that I have hijacked this line from Shelley’s ‘Ozymandias’. It conveys perfectly the sense of antiquity and timeless continuity I still feel when I gaze at my favourite guide to the past – mitochondrial DNA.

To explain, we need to go back thirty years to a key paper published in the leading scientific journal Nature by the New Zealand-born evolutionary biologist Allan Wilson from the University of California, Berkeley.1 Wilson and his team had taken placenta or cell lines from 147 women from all over the world and isolated DNA from the mitochondria. Mitochondria are components of our cells that reside in the cytoplasm, that part of the cell that surrounds the cell nucleus but is still contained within the cell membrane. They are integral components of the cell, but they have their own separate origin. Back in the distant past they were free-living algae that became engulfed by a primitive cell and have remained there ever since. Being originally separate organisms, mitochondria still retain their own DNA. Their special property is that they enable the cell to use oxygen to burn food. Until then, cells only had the apparatus for anaerobic metabolism and could not cope with atmospheric oxygen. With the help of their newly acquired mitochondria, however, cells could squeeze up to nine times as much energy from the same amount of food. In the early atmosphere, oxygen was toxic but mitochondria turned it into the life-giving gas upon which every animal species depends upon today.

The other unusual feature of mitochondria is that they are inherited only through the female line. The reason is that animal eggs are crammed full of mitochondria, while sperm don’t have any to speak of. To be entirely accurate, those few they do have don’t survive in the fertilised egg. This was the feature that appealed to Wilson and his team. Everyone inherits their mitochondrial DNA from their mother, who got it from her mother, who inherited it from her mother and so on back through time. Males and females have mitochondrial DNA – after all they both need to breathe oxygen – but only females pass theirs on to their offspring.

In complete contrast to mitochondria, the DNA in the cell nucleus is inherited more or less equally from both parents. This nuclear DNA controls most of the body’s functions, with the important exception of aerobic metabolism, which remains the responsibility of the mitochondria and its DNA. Unfortunately, ancestral connections traced backwards by nuclear DNA soon become extremely complicated. We all have two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents and so on. The number of ancestors doubles with each past generation, so by the time we go back only twenty generations, that’s about four hundred years for humans, we have over a million ancestors. It’s very unlikely that we have inherited DNA from all of those thanks to the random mixing of nuclear DNA with each generation, something I shall explain later in the book. Even so, we will have inherited DNA from a great many of them, but from whom we will never know. In comparison with this genetic muddle, there was only ever one woman in each generation who is our mitochondrial ancestor and whose DNA we have inherited. It is that simplicity which drew Allan Wilson to investigate mitochondrial DNA (or mDNA for short) rather than nuclear DNA in his representative sample of the world’s population.

The striking conclusion of this work was that if you went back far enough, everyone on the planet has inherited his or her mDNA from just one woman. In ways that we will come on to, Wilson estimated that she lived in Africa about 200,000 years ago. Unsurprisingly, she was immediately dubbed ‘Mitochondrial Eve’. The results also showed a clear connection between Africans and everyone else, suggesting that modern humans spent a long time in Africa before some of them left to populate the rest of the world. It’s as well to remind ourselves here that we are only considering strict female–female matrilineal inheritance, with no consideration, for now, given to the DNA from men.

It was a delightfully simple conclusion, although some people still find it confusing. Eve was certainly not the only woman alive at the time, just the only one to have direct matrilineal descendants living today. As now, couples can have only sons or no children at all, but it is only daughters who can pass mitochondrial DNA to the next generation. It follows that in the 10,000 or so generations since Eve, the only mDNA to survive to the present day has been passed along unbroken matrilineal lines, while that from Eve’s many contemporaries has been eliminated at some point along the way.

Though there have been some modifications in the ensuing thirty years, this overall concept of Mitochondrial Eve has stood the test of time. Wilson’s 1987 paper became a model for all future molecular genealogies, which have completely revolutionised our view of human origins. I analyse mitochondrial DNA samples from all over the world, and marvel at every one of them. They have each travelled unseen for tens of thousands of years in the cells of a continuous line of ancestors from ancient times until today when, at last, they reveal their secrets in the laboratory.

It took ten years before the Los Angeles-based biologists Robert Wayne and Carles Vilà published an equivalent genetic analysis for the dog.2 Like Wilson, they used mitochondrial DNA, but with a more advanced technique that examined the DNA sequence itself rather than the limited summary that was all that had been available to Wilson a decade earlier. I will say more later on about DNA sequences, including what they are and how to read them, but for now we will concentrate on the dogs.

Wayne and his team collected an impressive set of samples. In addition to 140 domestic dogs from 67 different breeds, Wayne also included wolves, coyotes and jackals in his analyses. The wolf collection came to a total of 162 animals from 27 locations worldwide. In addition, because they had been mooted as possible ancestors of modern dogs, Wayne included 5 coyotes and 12 jackals – 2 golden, 2 black-backed and 8 simien. When the mDNA sequences from all these animals were displayed in a molecular tree (referred to as Wayne’s tree) in the same way that Wilson had portrayed the human mitochondrial genealogy, the resemblance between the two was clear to see.

Wilson’s human tree (see here) divided the world population into two main branches, one African and a second containing both some African and all the people from outside Africa before coalescing on a single matrilineal ancestor – ‘Mitochondrial Eve’. The Wayne dog DNA tree consisted of four main branches, each with a different, but still closely related, ancestor. Most dog breeds were placed in the major branch, which Wayne called branch I, and included many of the common breeds as well as some so-called ‘ancient breeds’ like the dingo, New Guinea Singing Dog, African Basenji and Greyhound. Branch II contained two Scandinavian breeds, the Elkhound and the Jämthund, while branch III included a variety of breeds such as the German Shepherd, Siberian Husky and Mexican Hairless. Finally, branch IV included Wirehaired Dachshund, a Flat-coated Retriever and an Otter Hound. This last branch also contained a few wolves, one of which, from Romania, was the only wolf in the whole study whose sequence exactly matched that of a number of dogs including a Toy Poodle, a Bulldog and, surprisingly, another Mexican Hairless.

The simplified diagram (see here) only shows the major mitochondrial groups. Within each circle are a number of breeds. They are not shown here but can be inspected in the original,3 where there are many examples of exactly the same mDNA sequence being found in several different breeds. For example, a Norwegian Buhund, a Border Collie and a Chow Chow had precisely the same mitochondrial DNA sequence. Equally, the same breeds could have different mDNA sequences and appear on different branches of the tree. For instance, the eight German Shepherds had five different sequences between them. We will consider what this means a little later.

Wilson’s Human Tree (simplified). (Image courtesy of Professor Bryan Sykes)

Wayne’s Dog Tree (simplified). (Image courtesy of Professor Bryan Sykes)

Had Darwin been alive to read it, he would have been itching to know where wolves, coyotes and jackals fitted into the tree, if at all. The answer was very clear. The coyote and jackal fell out of the main wolf/dog tree, as it were, immediately. Their DNA sequences were clearly quite different to all the dogs, and none made it into any of the four major branches. When it came to placing the wolf DNA sequences, the answer was equally striking, not because they were outside the dog tree but because they were deeply embedded within it. There was no doubt, from the mitochondrial DNA analysis, that all dogs were descended from wolves and from no other species. It was the first triumph of molecular genetics as applied to dogs – and by no means the last.

Darwin wasn’t wrong about much, but, by means he could never have foretold, his statement on dogs that ‘We shall probably never be able to ascertain their origin with certainty’ would turn out to be one of those rare exceptions. I am sure he would have been utterly delighted to be proved wrong.

Turn the clock forward another ten years to the present day and the Wayne dog tree is still alive. But, like the technical improvements we have considered in the decade between the Wilson and Wayne papers, there have been great strides in DNA analysis in the last ten years, which have led to some radical pruning of the original tree, while leaving the major branches intact.

Before we turn to the effect of these improvements in filling in the blanks in our knowledge of dog evolution there is one other important genetic system to consider. This is the Y-chromosome, the mirror image of mDNA in a genealogical sense in that it traces not the maternal but the paternal genealogy through time. Again the reason is simple enough. Only males have Y-chromosomes and they pass them on exclusively to their male offspring. In many species it is a less reliable witness than the mitochondrial equivalent because of the very variable mating success of males. In most species, including our own, males have the potential to father virtually unlimited numbers of offspring, or none at all, but females are restricted to just a few. This has major implications when we come to look at pedigree dogs.

Just as any conclusion about evolution based on mitochondria should carry the caveat that it can only reveal patterns based on females, so the Y-chromosome only traces the origins of males. Of course, ultimately they both have to tell more or less the same story, but there are fascinating twists and turns along the way.

In any sort of genetic analysis it is vital to be able to detect inherited variation, which is the lifeblood of genetics. Variation comes in many different forms – blood groups, hair colour, height or DNA sequence. You simply can’t do any genetics without it. For DNA the variation in sequence can be read directly, as it is for most mDNA comparisons, or it can use what are known as genetic markers. These are places where the sequence between, in this case, different Y-chromosomes, is known to differ. You can then test for the markers directly without having to sequence the whole chromosome, which saves a lot of time and money. But before you can use them you have to find them, which used to be an enormous bore. It is much better now, as we shall see.

The tedious process of discovering dog and wolf Y-chromosome markers was slow to get going and the first studies used a panel of only four markers. Luckily Y-chromosomes alone are spared the process of shuffling with other chromosomes, something else I will explain as we go along, and so the markers can be combined as blocks. So four markers (A–D), with two versions at each one (1 or 2), can differentiate sixteen Y-chromosomes (A1, B2, C1, D2; A2, B1, C2, D1 and so on), meaning that you can do a lot with just four markers and sixteen combinations.

A group from Sweden was the first to publish any wolf and dog results from this kind of analysis, having studied both Y-chromosomes and mitochondria in 314 dogs from 109 different pedigree breeds.4 Their wolves came from six different regions in Europe and North America, a total of 112 animals. And of course, for both dogs and wolves, all the animals were males. It came as no great surprise after the Wayne mitochondrial pattern (as illustrated here) to find that the dog and wolf Y-chromosomes were similar. Also, there was no sign of any other species, as was always a formal possibility when only the mDNA results were known. Had the original dogs been hybrids between female wolves and male jackals, for example, this would have been invisible to mDNA analysis but not to that of the Y-chromosome. The confidence that wolves really were the only ancestors of all dogs increased substantially after the Swedish study.

In a similar fashion to mDNA, the same Y-chromosome, as defined by its genetic markers, was to be found in several different breeds of dog. As an example, an identical Y-chromosome was found in a Bernese mountain dog, a Border Collie, a Dalmatian, a Greyhound, a Poodle, a Shetland sheepdog and a West Highland terrier. On the other hand, different individual dogs of the same breed often had several different Y-chromosomes. Five Collies, for example, were found to have three different Y-chromosomes between them.

The comparison of the male and female genetic contributions showed quite clearly that in domestic dogs there were many more different mDNA sequences around than there were different Y-chromosomes. What that meant became clear when the wolf results were compared. In wolves the number of different mDNA and Y-chromosome sequences was about the same, not skewed as in dogs. This is very familiar scenario in many human populations where there are lots of different mDNA types but fewer Y-chromosomes than there should be if breeding success was roughly equal across the sexes.

Wolves are almost entirely monogamous, with only one breeding male and one breeding female in a pack. As a consequence males and females make an equal overall genetic contribution to successive generations and, as the Swedish team found, this balances the mDNA and Y-chromosome diversity. In pedigree dogs, the situation is more like some human populations where a few males have a disproportionate number of offspring. The ultimate human example is Genghis Khan, the thirteenth-century Mongol emperor who has an estimated 16 million male descendants living today, each of them carrying his Y-chromosome. Genghis Khan achieved this feat by slaughtering his male enemies defeated in battle and inseminating as many women as possible, often to the point of exhaustion. ‘Try spending the night alone from time to time,’ his doctors cautioned. When he died in 1127 Genghis passed on his wealth, and his habits, to his sons. Male dogs can achieve similar breeding success with considerably less effort than Genghis Khan. All they have to do is win ‘Best in Show’ and let the breeders do the rest.

At first it was a puzzle as to why pedigree breeds showed little or no sign of a common origin, at least as far as mDNA and Y-chromosomes were concerned. Surely with all the care taken to make sure pedigree dogs breed true, all dogs within a breed should have the same origins along both male and female ancestral lines. Not so. Instead, there seemed to be no telling, short of DNA testing, to which mDNA or Y-chromosome branch any particular dog belonged. Certainly, the breed could not be predicted from the DNA results from either system.

Although the scope of mDNA and the Y-chromosome is limited to just two genetic systems, we must not make the mistake of underestimating the importance of mitochondrial DNA and the Y-chromosome in crashing through the barriers of uncertainty surrounding the origin of the dog. Scientists from Darwin onwards have pondered this question with no means of coming to a definite conclusion. Were jackals or bush dogs or wolves or coyotes or foxes or hyenas or some other animal, possibly long extinct, the true ancestors of the modern dog? The research, first with mitochondrial DNA and then with the Y-chromosome, has made the answer crystal-clear. Wolves, and only wolves, are without question the ancestors of all living dogs.


On the Origin of Wolves

The genetic trees drawn with the help of mitochondrial DNA and the Y-chromosome make it very clear that the only ancestor of all dogs is the wolf. There is more we can decipher from the DNA results, but before we come to that, what do we know about the ancestry of wolves?

The Age of the Mammals began in the Cretaceous period following the sudden extinction of the dinosaurs some 65 million years ago. This extinction left a big gap in the fauna which was gradually filled by mammals, which until then had been an inconspicuous group of small furry animals cowering in the undergrowth. Their numbers increased, and by 40 million years ago, during the Eocene epoch, the emerging mammals began to evolve into today’s familiar groups: horses, deer, elephants, apes, dogs and cats, early forms of modern Orders.

Wolves, and therefore dogs, belong to the last of these Orders, the Carnivora. It has become the most diverse of any Order, embracing over 280 species, and it takes its name from the Latin that describes the main characteristic of its members: ‘flesh-eating’. They are the carnivorans, as distinct from the general term ‘carnivores’, which takes in all meat-eating species, be they fish, reptiles or even plants. A major division of the Order Carnivora is the Family Canidae, which includes wolves, coyotes, jackals and foxes. Cats large and small belong to the Family Felidae, bears and pandas to the Ursidae, while badgers, hyenas and seals belong to other, separate, families. Some carnivorans, like the Giant Panda, are strictly vegetarian but are still included within the same Order. It is their teeth that set the Carnivora apart from other mammalian Orders. All have well-developed third incisors, which serve to pierce the flesh of prey animals to prevent escape and to kill, while unique to carnivorans are their fearsome carnassial teeth, taking the place of our molars. Carnassial teeth are razor sharp and self-sharpening and are designed to slice through flesh like a pair of shears rather than merely tearing at it.

The dog-like carnivorans, the Canidae, and the cat-like Felidae began to diverge from each other and become gradually more specialised. As far as we can tell from the fossil record, the earliest canids evolved in North America where the oldest fossil dog, Cynodesmus, was discovered in Nebraska, USA, and lived between 33 and 26 million years ago. At one metre in length, it resembled a modern coyote and, by its dentition, was clearly carnivorous with large canine teeth for grasping and tearing the flesh of its prey. Soon after, on an evolutionary timescale, some truly fearsome carnivores began to evolve, including the bone-crushing Cynarctus. As these monsters became extinct about 11 million years ago they were replaced in turn by other canids, notably Tomarctus, found all over North America from Florida, north to Montana, west to California and south to Panama. From the size of the jaw muscle insertions in their skulls it is clear that Tomarctus had a bite strength far greater than required to kill its prey. This led to the conclusion that, like modern-day hyenas, Tomarctus was able to crush bones to reach the nutritious marrow of scavenged carcasses.

By the middle of the Miocene epoch, some 10 million years ago, the canids had spread from America, first to Asia, then to Europe and finally to Africa. As they did so, the ancestors of today’s wolves gradually evolved towards a lighter, faster frame in order to hunt swift herding prey like elk and wild horse. They hunted not as individuals but as members of a pack. Thus began the key development in the evolution of the modern wolf, and ultimately of the domestic dog. To be effective hunters they developed the ability to communicate with each other and to work as a team. Wolf packs travelled with the herds, following them throughout the year, a habit that our own human ancestors adopted.


The Living Fossil

All our efforts to reconstruct the past can only ever give an approximation of what really happened. Well-preserved fossils are spectacular but rare and their discovery can only ever convey a patchy record. History is notoriously inaccurate, depending on the inclinations of the author. Mythologies require sophisticated interpretation. Genetics is no different. It is just another foggy lens through which we try to make sense of times gone by. Bearing that in mind, let us clean the eyepiece and take another look.

In Chapter 3 we saw how DNA from living dogs and wolves was able to reconstruct a plausible genetic relationship between the two. These were inferences from modern DNA but, astonishingly, DNA can survive for thousands of years in fossil bone and teeth. As we will see later, it is often in a pretty bad state. Nonetheless it does give us the chance to examine ancient sequences directly rather by inference. Later on, we will have a closer look at how ancient DNA has helped us follow the evolution of the dog. But before that we need to know a little more about DNA itself.

All genetics depends on mutation, the ultimate source of all variation. DNA changes over time. When a cell divides, its DNA is copied so that each of the two daughter cells contains the full set of genetic instructions. The copying process is astonishingly precise and accurate, and the error rate is minuscule. Editing mechanisms within each cell scan the copies for errors and correct them. But the error rate is not zero. After each cell division, roughly 1 in 1,000 million mutations gets through uncorrected. If the emerging mutation changes a vital component of a gene, then the daughter cell will either malfunction or die. Only extremely rarely will a mutation be beneficial. The most dangerous malfunctions are those that turn normal cells into malignant ones which lose the capacity to restrain their own cell divisions, and they develop into tumours. That is why in some rare diseases, where the DNA editing and correction capacity of cells is faulty, it leads to much higher rates of malignancy.

Fortunately, the majority of DNA copying errors has no consequences whatsoever; first, because the errors don’t occur in important genes, or, second, because they are not passed to the next generation. Only mutations in the germ line, being the cells that go on to form eggs and sperm, are capable of travelling on through time. Even then, the vast majority of sperm never get to fertilise an egg, and, in mammals, most eggs are not fertilised anyway. For these reasons alone, the overwhelming majority of germ-line mutations which occur through faulty copying, even the most potentially damaging of them, are not passed on.

Some mutations, however, do get through to the next generation. Most will not be noticed and have no significant effect on the body, either because they occur in unimportant genes or in the gaps between genes in the long stretches of DNA whose function, if any, is still largely unknown. Here it is worth distinguishing between genes and the rest of our DNA. Genes do something, usually instructing cells how to make proteins. There will be more on this when we take a look at gene mutations that have been found in dogs, but for now we will concentrate on the inconsequential mutations that have no effect, neither good nor bad. Precisely because they are so inconsequential, these unassuming ‘neutral’ mutations are the lifeblood of the sort of genetic reconstructions of past events that we have covered so far. A damaging mutation in a vital gene will disadvantage the individual who carries it. Not necessarily fatally, of course, but enough to put him or her at a slight reproductive disadvantage and thus reduce the prospects of the mutation being passed on to the next generation. Generally, over time, the mutant gene will be eliminated by selection, though not always, as we shall see in pedigree dogs. However, the humble and meaningless mutations that have no effect on anything of great importance will escape the scrutiny of selection and will sail on unmolested through future generations. It is these humble mutations that are the guiding lights that illuminate the history written in the language of the genes.

To explain how mutations are used, in dogs and humans, to date past events like the timing of the transformation from wolf to dog, let us imagine a desert island in the middle of a vast ocean. A young couple arrives in a canoe. For our purposes, it could equally well be a couple of shipwrecked dogs. The island is a paradise, with plentiful fresh water in bubbling streams flowing down from high mountains in the interior. There are coconut palms, shellfish and crabs in the sea and no predators or dangerous animals to disturb the idyll. Everything needed for life is on hand, and the couple start a family. Their children grow up in this cradle of abundance and, ignoring incest taboos for the sake of this exercise, have children with their siblings.

Time passes. The population settles down to a stable total of 1,000. Nobody leaves the island, there is plenty for everybody, and no one else arrives. Until one day a scientist and a research assistant turn up and begin taking a DNA sample from each of the inhabitants. The samples go off to the lab and the sequences are read. A few weeks later the scientist and his assistant, now back home, get the results. What can they deduce about the people on the island from the results? It doesn’t matter all that much which genetic markers we are talking about for this example to work, so let’s keep it simple and imagine that we are working with mitochondrial DNA. The first things the researchers notice is that everyone’s DNA sequence is very similar. Some sequences are identical, and we will call that the ‘core’ sequence of the island. However, about half the people have a sequence that differs at just one DNA base from the core.

DNA sequences are written using a childishly simple alphabet with only four letters. These letters represent simple organic chemicals, or bases, joined together in a linear sequence. Their abbreviations are even simpler : A, G, C and T. Any DNA sequence is a long string of these bases: … CCGGTAA … and so on. A mutation might change a T to an A, making the new sequence read as … CCGGAAA … The language may be child’s play, but the meaning is far from simple, as we will explore further in a later chapter, but not now. Instead we travel back to our island.

Of the 1,000 people who were tested, 500 have the core sequence and 500 have a one-base difference from it, but not all at the same one.

The researchers draw the reasonable conclusion that everybody on the island is ultimately descended from one couple, or rather from one woman, as we are dealing with mitochondrial DNA. Can they tell from the results how long ago the island was settled? To get an answer, we need to agree a very important factor. The mutation rate. That is the rate at which mDNA mutations occur and get passed on. It is going to be an estimate, drawn from other results. The factors which contribute to the estimate are sometimes astonishingly crude.

A common approach is to take two species, say human and chimpanzee, compare their DNA sequences and make an assumption about how long it is since they last shared a common ancestor. In this example the usual figure is 6 million years, based on fossil evidence which, for both species, is extremely flimsy. All genetic dating of past events depends crucially on the accuracy of the mutation rate and that it has remained stable over the period.

Fortunately, the estimates of the mitochondrial DNA mutation rate by the various methods come up with a figure that most are happy to accept. For the segment of mitochondrial DNA that Wayne and Vilà used, the rate is estimated to be one base change every 20,000 years. Mutations occur randomly as cells divide, so we must turn to discussing probabilities. A mutation rate of one per 20,000 years doesn’t mean that no mutations occur until that time has passed. It is an average. It could happen in the first generation or the last or, more likely, somewhere in between. Let us say the time between generations on the island is twenty years. If a quarter of the population has a mitochondrial DNA sequence that is one mutation away from the core, the average number of mutations per person across the whole island is then one quarter. The estimated time from first settlement then becomes the average number of mutations (a quarter) from the core, multiplied by the mutation rate (20,000), which comes to 5,000 years.

Returning to our scientists, they go back to the island to inform the council of elders of their results of the project. They also reveal that the original settlers had come from the mainland far away to the east because that is where they have also found the core mDNA sequence among the inhabitants. After listening politely to the presentation, the elders turn to the scientists and, as I have experienced first-hand, they say, most politely, something like ‘Thank you for your trouble. We knew that all along.’

In my deliberately simplified example we were dealing with just one segment of DNA on an island originally settled by only one couple. No one arrived or left for millennia. It doesn’t get any simpler than that.

Let us now suppose that other things happened on the island. Perhaps half the population died in an earthquake, or the central volcano erupted, destroying the crops, and three-quarters of the people starved, or an epidemic killed 90 per cent of the population. These are the sorts of catastrophes which might have happened in real life. Those events can severely distort our calculations. For instance, and let’s make it extreme, a tsunami kills everybody on the island except a couple who were far out to sea fishing at the time. They survived and, over time, their offspring repopulated the island. In this scenario, the genetic calculations would give the time that had elapsed since the tsunami rather than since the original settlement. The island would have undergone a ‘population bottleneck’. There would be no way of telling, by genetics alone, for how long the island had been settled before the tsunami struck. If we introduce further complexity, like a few boatloads of new arrivals, then all hope of being precise about the original settlement date goes up in a puff of smoke.

Given these unknown and often unknowable factors, I take claims of accurate genetic dating of past events with a large pinch of salt. That does not mean they lack value, but it is a mistake to become a slave to such calculations. We will use the island metaphor again when we come to consider the origins of pedigree dog breeds. Wayne and Vilà also used this kind of calculation to estimate the timing of the wolf–dog transition. The answer was much further back than anyone suspected, between 76,000 and 135,000 years ago.


Let the Bones Speak

At some point in the past the lives of wolf and human became intertwined and it is from this partnership that the dog eventually emerged. Until genetics entered the fray, the only way of following this transition through the intervening millennia was through fossils. Good fossils are in short supply and the fossil record is understandably full of gaps.

In terms of time, the oldest skulls that could even remotely be differentiated from wolves were excavated in the Goyet cave in southern Belgium in the 1860s. Like all good fossil sites, Goyet is a limestone cave whose alkaline environment helps to preserve the calcified bones and, importantly, any DNA that might lie within.

From studying the style of stone and bone tools found there, it was clear that the cave had been occupied by humans for a very long time. Neanderthals lived there during the time of the Mousterian culture, which lasted from about 160,000 years to 40,000 years BP (the standard archaeological abbreviation for ‘before present’). It takes its name from the rock shelter at Le Moustier in the Dordogne region of central France. The Mousterian lasted until the arrival of modern humans, our ancestors, about 40,000 years ago. As is not uncommon with early excavations, disturbance of the layers within the cave made precise stratigraphic dating of the different artefacts found there problematic. However, carbon-dating of the fossils gave precise dates for the organic remains at least. The cave fauna was a rich assemblage of cave bear, cave lion, horse, reindeer, lynx, red deer and mammoth. In the deeper recesses of the cave archaeologists found the skull of a ‘large canid’ carbon-dated to 31,700 years BP. Was it a wolf or was it a dog?

Of course, there must have been a period after the first wolf was adopted into a human band when its skull was exactly the same as a wolf’s – because it was a wolf. There was no exact moment of transition from one to the other, and the whole debate has a strong flavour of semantics. The more cautious authors merely refer to these intermediates as ‘canids’ or ‘wolf-dogs’, thereby sidestepping the argument altogether.

A similar conundrum faced archaeologists excavating the nearby site of Trou des Nutons, a cave formed in the limestone hills of the Ardennes by the River Lesse, a tributary of the Meuse. Among the fossils found in the Trou des Nutons were beaver, roe deer, horse, bison and wild sheep, suggesting a later occupation than at Goyet. This was confirmed when another skull of a mystery ‘large canid’ was given a carbon date of 21,800 years BP. This is a surprisingly early date and in the middle of the last Ice Age. But was it the skull of a dog or a wolf?

These skulls from France were subjected to a series of precise measurements of snout-length and width, the length of the tooth row and the size of the flesh-shearing, self-sharpening carnassial teeth that wolves and dogs have where we have molars.

Fossil canid skulls from two archaeological sites in Russia and Ukraine, one at Mezin (Ukraine) and the other at Avdeevo just over the Russian border, were given the same treatment. These two sites were inhabited by early humans who constructed huts of mammoth bones and left behind an abundance of beads and other artefacts carved from mammoth ivory. The objective of the osteometric study of candid fossils from these two sites was to discover whether the remains of these ‘large canids’ differed sufficiently from wolves in their skull morphology to be classified as dogs on their way to domestication rather than unmodified wolves.

To complete the comparisons, the analysis was extended to include later, but still prehistoric, unambiguous fossil dogs from France and Germany. Also included were a selection of modern and fossil wolves from Europe and Asia along with modern dogs from several large breeds including Great Dane, Tibetan Mastiff, Siberian Husky, Chow Chow, Irish Wolfhound, Malinois, Dobermann Pinscher and German Shepherd.1

Comparing multiple skull measurements from dogs of different sizes is a complicated business, and I will spare you the details of the multivariate analysis and go straight to the main conclusion. The Palaeolithic skulls from the oldest sites, including Goyet at 31,700 years BP, had a significantly different shape from modern, or indeed fossil, wolves. This suggests that, even by that early date, these animals were dogs already on the way to modification through ‘domestication’. An alternative explanation, though in my opinion rather less likely, is that these were the skulls of one or more wolf species that later became extinct. As we shall see later, there is other enticing evidence to support the former scenario and suggest that the close association between wolf and man began a very long time ago.

The next layer of evidence about the changing appearance of domesticated dogs comes from the late glacial period around 17,000 years BP, when the ice sheets covering northern Europe were fast retreating. The shrinking tundra no longer supported herds of large prey animals. The climate warmed considerably, rainfall increased and forests covered much of the formerly open tundra. The fauna changed with the landscape and many prey animals disappeared. Mammoths, woolly rhinoceros and their predators, the sabre-tooth tiger and cave bear, were forced into extinction. Others, like the wild horse, reindeer and bison, shifted their ranges. Humans began to spread north, first following the shrinking herds and later, as they entered the Mesolithic period, changing their diet to smaller woodland prey, like wild boar, pine marten, red and roe deer. On the coastal settlements, shellfish became a major source of food and the first boats ventured out to sea to catch fish. Supplementing this meagre protein diet were roots and tubers, insects and snails. The heroics of the mammoth hunt became a thing of the past and life became a gruelling fight for survival.

The close cooperation between human and dogs, by now thoroughly assimilated into human society, continued even though the superbly effective working partnership that had developed in the Upper Palaeolithic was at its best when killing large prey, a practice which by now was rapidly disappearing.

Around 12,000 years BP much smaller dogs made their debut in the fossil record. A team of French archaeologists found the remains of thirty-nine dogs at the Pont d’Ambron rock-shelter in the Dordogne. From an osteometric analysis similar to that carried out at the earlier sites of Goyet and Trou des Nutons in the Ardennes, it was clear that the Pont d’Ambron dogs were considerably smaller. The same was true with the remains excavated at the Montespan cave in the northern foothills of the Pyrenees and at the open-air site of Le Closeau in an old channel of the River Seine.

The authors of the exhaustive paper summarising this body of work confidently concluded that they were dealing with the remains of dogs and not wolves. In France at least, and also in Spain, dogs were clearly changing. In Russia, however, at around the same time, wolf-dogs were still very large. Whether this was a result of separate wolf domestications in the two regions or for some other reason, it was impossible to say. One firm but rather grisly conclusion, drawn from cut-marks on the bones of the Pont d’Ambron dogs, was that they had been butchered and, presumably, cooked and eaten.

As well as the issue of timing, the identification of the geographical location of the wolf–dog transition has absorbed many researchers and continues to do so. The first scenario to be proposed, by a group from the University of Konstanz in Switzerland led by Peter Savolainen, was that the major ‘domestication’ event happened only once, in East Asia.2 This was the conclusion of an mDNA study of 654 dogs from different regions of the world where the focus was on the diversity of sequences. The perfectly sensible rationale was that the highest diversity, that is the highest number of different mDNA lineages, would be found in the places where dogs had been around the longest and had the most time to accumulate new mutations, rather like the islanders in our metaphorical example. Savolainen’s team found mDNA sequence diversity was highest in south-east Asia and located the first ‘domestication’ to the region. This was a very controversial conclusion at the time, and it would be another decade before the debate was settled, although it still rumbles on in some quarters.3

In order to make progress on the vexing issues of timing and location, scientists turned to the DNA that had, incredibly (a word I do not use lightly), survived in fossils. Robert Wayne, who headed the Los Angeles lab, was one of the eclectic bunch of scientists who dared to think, against all reason and common sense, that DNA might survive in fossils. As there was no academic tradition of ancient DNA science and this was an entirely new field, the early pioneers came from all sorts of backgrounds. Svante Pääbo, for example, who went on to sequence Neanderthal DNA, was originally an immunologist with an interest in Egyptology that led him to attempt to extract DNA from mummies in 1985. Ed Golenberg, who claimed in a 1990 Nature article that he had extracted DNA from a 17-million-year-old magnolia leaf, was a botanist. Scott Woodward, in a paper published by Science in 1994, reported DNA extraction from a fossil dinosaur Tyrannosaurus rex from the Cretaceous period entombed in a block of coal. Woodward was a geneticist from Brigham Young University in Utah who went on to run a large genetic genealogy project for the Mormon Church. My own background was in medical genetics, specifically the causes of inherited bone disease. In 1989 my colleagues and I reported the first recovery of ancient bone DNA in Nature.

We met regularly to feel our way in this exciting but tricky field where extravagant claims could be accepted for publication by the very best journals – and, more often than not, be rapidly dismissed. Robert Wayne was a regular attendee at these meetings. He is an evolutionary zoologist with an interest, at the time, in the hybridisation of wolves and coyotes where their ranges overlapped. Robert has gone on to become the pre-eminent scientist in dog genetics, first with work on fossil DNA and then with extensive analyses of the genetic variation in living dog breeds. Much of what we know about the genetics of dog evolution comes from Wayne’s lab in Los Angeles. I was slightly surprised to discover that Wayne doesn’t own a dog, but he does have a cat.

Once the field settled down in the years following the initial papers on ancient DNA recovery, a number of labs began to report its successful extraction from fossil wolves and unambiguous dogs, sometimes of great antiquity.

The field advanced in fits and starts, at first with the publication of single cases, then a few related finds and eventually, in 2013, a large series that seems, for now, to have settled the question of the origin of the wolf–dog transition in favour of Europe between 19,000 and 32,000 years ago.4

In the first decade of this century, the protocols for recovering ancient DNA improved a great deal and it became realistic routinely to obtain long sequences from old bone. Once again mitochondrial DNA was the target, for the very good reason that there are far more copies in a cell compared to nuclear DNA. If you are working at the limits, as you always are with ancient DNA, you want to make things as easy for yourself as possible.

DNA sequencing technology had also advanced to a point where it became practicable to sequence all 16,727 bases of the canid mitochondrial genome from fossils. Analysing the complete sequence avoided the potential bias of restricting the analysis to the shorter ‘control region’ used in the earlier papers by Wayne and Vilà and by Savolainen. The large 2013 study used more or less complete mitochondrial sequences of eighteen fossil ‘canids’ along with a large collection of modern dog breeds. Although not every specimen yielded all base pairs of sequences, it was enough to place them accurately on the evolutionary tree. Nuclear DNA, conversely, was too badly preserved to be of much use.

The resulting tree, or phylogram, to use the proper name, again recognised the four main branches (I–IV in the figure here) of modern dog breeds initially published by Wayne and Vilà. The results were fascinating. The fossil dogs on three of the four branches (I, III, IV) of the tree are closely related to modern breeds while the rare fourth, mainly Scandinavian, branch (II) is closest to modern wolves from Sweden and Ukraine. One possible explanation is that dogs on this branch, which include the Norwegian Elkhound and the Jämthund, acquired their mitochondrial DNA from wild wolves in the recent past, after the advent of agriculture.

While all of the ancient dog lineages have survived to the present day, that is not the case for the fossil wolves. Many of these lineages are now extinct or have simply not been picked up in living wolves yet, though the likelihood of that diminishes as more and more modern wolves are sequenced.

There is a wealth of fascinating detail in the 2013 paper by Olaf Thalmann, which I encourage you contemplate at your leisure from the original publication.5 I do, however, want to mention one particularly surprising finding – about dogs in America. Only two fossil dogs were sequenced, one from Argentina and the other from Illinois, USA. From these mitochondrial sequences these dogs were clearly both related to branch I European dogs, though the ages of the fossils (1,000 and 8,500 years BP respectively) mean that they must have arrived well before the first European settlement in the fifteenth century. These dogs accompanied the indigenous Native Americans who had arrived earlier from Asia. None, however, had mitochondrial DNA remotely like that from American wolves. This has to mean that Native American dogs were ultimately descended from European and not American wolves.

There was another surprise in store. Breeds thought to have been descended from indigenous ‘Pre-Columbian’ dogs, like the Chihuahua and Mexican Hairless, also had an exclusively European mitochondrial heritage. Although sample numbers are quite low, it does look as if the indigenous Native American mitochondrial lineages were another casualty of European settlement.

As the dust settles on the controversies still hovering over the timing and location of the transition from wolf to dog, one thing is certain. It all began a very long time ago.


The Cave of Forgotten Dreams

Though hardly fixing the dawn of the transition between wolf and dog with any degree of precision, the genetic dates are embedded in the bounds of what we call the Upper Palaeolithic – the last of the three phases of the Old Stone Age.

The origin of this classification, which is still used today, can be traced to John Lubbock, 1st Baron Avebury. A banker by profession, he also had a wide range of other interests including politics, biology and archaeology. His interest in the natural world grew from his friendship with Charles Darwin, who moved to the same village, Downe, in Kent, in 1842 when Lubbock was eight years old. As Lubbock matured, his interest in evolution and archaeology grew. He became an ardent supporter of Darwin’s evolutionary theories and of academic liberalism in general. He bought land in Wiltshire to save the famous prehistoric stone circle at Avebury from destruction and introduced into Parliament a bill that would eventually become the Ancient Monuments Act, the forerunner of all legislation to protect ancient sites.

Lubbock divided the Stone Age into two phases, the Palaeolithic, sometimes known as the Old Stone Age, lasting until roughly 10,000 years ago, and the Neolithic, the New Stone Age which followed it, coinciding with the invention of agriculture. Later an intermediate phase, the Mesolithic or Middle Stone Age, was adopted as the term for the period between the end of the last Ice Age about 17,000 years BP and the dawn of agriculture when the Neolithic began. About 4,000 years ago, the Neolithic gave way to the Bronze and then Iron Ages. The Palaeolithic was further divided into Lower, Middle and Upper phases, with the last of these lasting from about 50,000 years BP until the transition to the Mesolithic. Incidentally, the dates here only apply to the Stone Age in Europe. In other parts of the world the transitions occurred more recently; indeed, in highland New Guinea the Stone Age lasted until well into the twentieth century.

The genetic dating places the wolf–dog transition firmly within the Upper Palaeolithic, a quite extraordinary period in the history of our species, bristling with innovation and new ideas. The hallmark of the Upper Palaeolithic is the appearance of new forms of stone tools, the most durable of evidence. Until then, the only tools were hand axes and spear points. They were carefully made, certainly, but had not changed in basic design for tens of thousands of years. Suddenly, archaeologists were finding delicate arrow points, bone needles, even fish hooks, artefacts never seen in older, deeper layers.

Human fossils were much scarcer than stone tools, but they too showed a change from heavy-boned and robust skeletons whose skulls boasted prominent brow-ridges and receding chins to an altogether lighter and more graceful form. Was this a change brought about by slow adaptation, or was it the sign of the arrival in Europe of a new human species? After years of debate the argument was settled in favour of the wholesale replacement of the indigenous humans – Homo neanderthalensis, the Neanderthals – by a new arrival from Africa. This was Homo sapiens, our own ancestors. Mitochondrial genetics was the deciding factor in settling the argument in favour of replacement.

A few days before Christmas 1994 three speliologists, Eliette Brunel-Deschamps, Christian Heller and Jean-Marie Chauvet, were clambering over the face of the Ardèche gorge in southern France. Here the river cuts through the southern flanks of the limestone Massif Central on its way to join the Rhône near St-Just, well on its way to the Mediterranean. It is in the nature of limestone to form underground cave systems when exposed to the constant attention of slightly acidic groundwater. Over thousands of years the water gradually erodes the rock, hollowing out caverns of sometimes immense proportions.

The entrances to some 4,000 caves, many little more than overhangs, some as vast as medieval cathedrals, punctuate the steep walls of the gorge. Most are clearly visible, while others are hidden by rock-falls and vegetation. It was in order to find these hidden caverns that Jean-Marie Chauvet and his companions were inching their way along the steep sides of the gorge. They were searching for air currents emerging through cracks and crevices that would betray the presence of a cave system deep underground. At one point Chauvet felt a slight breeze coming from the rocks brushing the hairs on the back of his hands. He bent down to sniff the subterranean zephyr, then called his companions over. They agreed that the gentle flow smelled promisingly, damp, ancient and strangely alive. One by one they carefully removed the small rocks surrounding the vent until they came to a narrow cleft through which the air was escaping. It was too narrow for any of them to squeeze through, so next day they returned with hammers and a small pneumatic drill and set to work widening the crack. They found themselves faced with a narrow shaft descending into the black depths. Being experienced, not to say fearless, potholers they squeezed through the gap until they reached a point where a gallery opened out in front of them. It was clear, only from inside, that the main cave entrance had been blocked by an ancient rock-fall and that they had somehow found their way into the main cavern through the roof.*

As they explored the cave system over the following days the true wonder of their discovery began to dawn on them. Gleaming stalagmites rose up from the cave floor to meet their counterparts, delicate stalactites, suspended from the roof. Formed by the steady drip-drip-drip of calcium-rich water, their pristine condition showed that no animal or human had disturbed these hidden depths for thousands of years. On the floor lay scattered bones and skulls of cave bears petrified beneath a glassy coating of calcite.

This image actually comes from an exact replica of Chauvet cave that opened in Vallon-Pont-d’Arc in 2012, as access to the ancient caves is severely restricted for the protection of the artwork. The replica art was created using the same tools and methods as it is believed were used by the original artists. (Getty/AFP/Staff)

As Chauvet and his companions pushed further and further back along the galleries they saw in front of them the first of the paintings. Dozens of crude human hand prints outlined in red ochre covered one of the walls to a height of nearly two metres. These were only an introduction to the treasures which lay further back. There, on the deliberately smoothed cave walls, were drawn the images of lions, bears, mammoths, rhinoceros, horses and giant deer. These are the oldest morphologically accurate depictions anywhere in the world. What strikes home about them is their beauty. These are not merely crude outlines like the hand prints in the antechamber. They have form, expression and movement.

A painting from Chauvet cave that shows the head and horns of two aurochs, an extinct form of wild cattle that would have been a key prey animal for both humans and wolves. (JAVIER TRUEBA/MSF/SCIENCE PHOTO LIBRARY)

As well as being objects of wonder in themselves, these paintings have naturally led us to contemplate the reason they were drawn in the first place. What a task it must have been. Working deep underground without any natural light, the artists, for that is what they were, could only illuminate their lithic canvases by the light of glowing wooden torches. Streaks on the walls show where they had rubbed the dying embers to rejuvenate the flames. Carbon-dating the charcoal smeared on the walls was the means of discovering how long ago the drawings were made.

All organic material contains carbon, and this can exist in two forms called isotopes. Carbon 14 is very slightly radioactive. The other isotope, carbon 12, is not. After an animal or plant dies, or is burned in the case of the wooden torches, the radioactive carbon 14 slowly decays with a half-life of almost 5,000 years. In other words after 5,000 years there is only half as much carbon 14 remaining. By comparing the content of the two isotopes using a mass spectrometer to count the atoms, the age of the specimen can be estimated. Atmospheric carbon 14 is generated by ionising radiation from the sun high up in the atmosphere, some 32 kilometres above the ground. The proportions of the two carbon isotopes in the atmosphere are more or less in equilibrium. Thus the ratio of the carbon isotopes in a freshly dead animal or plant is equal to the atmospheric ratio at the time.

There are many factors that can change this ratio artificially and consequently introduce errors in dating. One is contamination of old material with modern carbon, for example from the archaeologists who recovered the specimen. This tends to make the material appear younger than it actually is. As is well known, carbon dioxide levels in the atmosphere have rocketed due to human activity since the Industrial Revolution. This carbon is ancient, coming as it does from the burning of fossil fuels that are millions of years old and no longer radioactive. This tends to reduce the carbon 14 in a specimen and artificially increase its apparent age. Nuclear testing also affects atmospheric carbon but in the opposite direction. Enormous amounts of carbon 14 are released into the atmosphere by a nuclear explosion, which in turn reduces the time estimate for radio-carbon dating. Nowadays these influences are incorporated into the calculations and the dates produced are referred to as ‘calibrated’. The original pioneers of radiocarbon dating did not take these influences sufficiently into consideration, and as a result many of the dates claimed in the earlier days of carbon-dating are wrong.

Thankfully, Chauvet cave was not discovered until the modern era of calibrated radiocarbon dating, and the dates obtained from the charcoal and other organic material in the caves can be relied upon. They show that Chauvet cave has been used for at least 80,000 years, first by cave bears, the skulls and bones of which litter the cave floor, then by an assortment of more recent Upper Palaeolithic mammals including hyenas and a couple of wolves.

There appear to have been two distinct phases of human ‘occupation’. The first was between 37,000 and 33,000 years ago and most of the drawings date to this phase. A later phase of occupation which produced the crude hand prints outlined in red ochre lasted from 31,000 to 28,000 years ago.

Chauvet cave is one of a handful of decorated caves from this remarkable and crucial phase in human evolution, the others being Lascaux in the Dordogne region of south-west France and Altamira in Calabria, northern Spain. Unlike the other two, Chauvet is in pristine condition, never having been open to any but bona fide researchers under strict instructions not to disturb the cave in any way. Altamira and Lascaux were open to the public for many years before the damaging effects of exhaled moisture and carbon were fully appreciated. They are now effectively closed to prevent further damage, though visitors can enjoy the visual impact of the caves and their paintings in nearby reconstructions.

In many people’s opinion the Upper Palaeolithic warrants comparison with other transformational periods in human cultural history: the rise of democracy in ancient Greece, the Italian Renaissance, the Age of Reason. So many new things were happening to the way we lived and most importantly to our interactions with the world around us. Many of these developments remain unseen and only reveal themselves in very special circumstances. Such a one is the discovery of Chauvet cave. There must be other caverns like it still sealed inside their limestone tombs, waiting for their breath to percolate to the outside. These caves give us rare glimpses into a vanished world, so very different from our own. Yet we see from the drawings that in many ways the artists were very much like ourselves. We understand the murals. Without difficulty we sense their beauty.

There are no human remains in Chauvet cave and, other than the drawings, very little sign of human presence. Nobody lived in Chauvet. What then was the purpose of these drawings, made with such effort and such skill? Clearly they were not purely decorative in the way we might hang a favourite painting on the wall above the fireplace. Although we will never know for certain, to many eyes these beautiful drawings are a tangible expression of a world of imagination and spirituality that marked the rise of truly modern humans.

An aspiration to go beyond what is absolutely necessary for function is also apparent in the stone tools our ancestors left behind. Whereas Neanderthals made perfectly functional tools like hand axes and thrusting spear points, they appear clumsy in comparison to the beautifully fashioned arrow points of the Upper Palaeolithic. The flint itself was traded over long distances and it supplied the raw material for individual craftsmen to demonstrate their skill. Fashioning a flint arrowhead or spear point was an opportunity not just to replace equipment lost in the hunt but also to demonstrate a high level of dexterity.

Quite suddenly, archaeological sites of the period were flooded with personal adornments. Excavations in south-west France reveal the appearance of bracelets, pendants and beads exquisitely fashioned from bone, antler and ivory. Seashells from the Mediterranean are found in sites hundreds of kilometres from the coast. Splinters of stone called burins were used to drill out holes in animal skins so that they could be sewn together with sinews for clothing. The effort involved was substantial.

Further afield at Sungir, 200 kilometres to the east of Moscow, archaeologists have excavated five human burials dated to 32,000 years BP, one of which contains the remains of a boy almost covered in strands of beads. There were nearly 5,000 beads in all, each one taking an estimated forty-five minutes to an hour to produce, a total of at least 4,000 hours in the making. On his head he wore a cap decorated with more beads as well as the canine teeth of at least sixty Arctic foxes. This was evidently the resting place of someone from an important family, a clear sign of social stratification emerging very soon after our ancestors arrived in Europe.

Our impression of our Stone Age ancestors is one of brutish simpletons clinging on in the face of appalling odds, surrounded by vicious and hungry predators looking for an easy meal. Certainly, their world was full of danger and life was hard. Nevertheless not every minute was taken up by the struggle to survive, and the evidence from Sungir shows that in some circumstances there was enough of a surplus for what we might imagine to be luxury, at least for a few. This was the world into which the wolf-dog was welcomed.

Far from being frightened prey cowering inside dank refuges, by the beginning of the Upper Palaeolithic our ancestors were well on the way to becoming top predators themselves. One by one the carnivores that once struck fear into the Neanderthals were driven to extinction. That perennial whipping boy of evolution, climate change, may have been the underlying influence behind the diminishing herds of mammoth and bison. But the climate had been changing for a very long time. Only when our ancestors arrived on the scene around 40,000 to 50,000 years ago did numbers of megafauna plummet. First the mammoth and the woolly rhinoceros vanished from the steppes, followed by the giant elk Megaloceros, then the bison and the wild horse. These were the herbivores that nourished the guild of carnivores and whose demise presaged their own extinction. The cave lion, leopard, hyena and sabre-toothed cat all vanished. The fearsome cave bear Ursus spelaeus who fought our ancestors for living space soon followed. Only the brown bear, Ursus arctos, managed to survive in the face of human competition by more or less abandoning meat altogether and restricting its diet to plants, berries and the occasional small mammal. At the end of the Palaeolithic all the large mammals, herbivores and carnivores alike, whose images jostled for space on the lime-smoothed walls of Chauvet, were gone.

A parallel wave of extinctions swept North America once humans arrived in numbers. As a species, we have never been good at taking responsibility for the damage we inflict, and the role humans played in the extinction of the North American megafauna is hotly debated. There is no doubt in my mind that both in Europe and in America it was our own human ancestors that pushed species after species over the edge into oblivion. In Europe none survived the hunting onslaught of our ancestors, but in North America, when the mammoth and the woolly rhinoceros went under, the elk and the buffalo survived.

Although technical invention in hunting equipment no doubt helped our ancestors to become the top predators, there was more to it than that. Certainly, the atlatl or spear-thrower was a deadly innovation which allowed our ancestors to kill at a distance and avoid injury, though alone it was hardly enough to account for the decimation of the megafauna. This piece of equipment was certainly one ingredient in our progress towards dominance of the Upper Palaeolithic world, but it seems unlikely that we achieved this distinction just because we could throw spears further and with more force than before. It was the revolution in our minds that took place all those years ago, as witnessed by the lavishly decorated burials of the children of Sungir and the gleaming frescoes of Chauvet, that really made the difference.

Artwork of how a spear-thrower (or atlatl) is used to throw a feathered dart. At top and centre, the dart is loaded. At bottom, it is being thrown. The angular momentum imparted means dart speeds of 150 kilometres per hour can be achieved, making this a lethal weapon in the hands of a skilled hunter. In the background is a cave painting of an animal wounded by an atlatl dart. The earliest such weapons were found at Schoningen, Germany, in the 1990s, dating to over 300,000 years ago. (KENNIS AND KENNIS/MSF/SCIENCE PHOTO LIBRARY)

In a narrow gallery towards the back of the Chauvet cave complex is a tantalising glimpse of another secret of this revolution. Impressed in the soft sediment that forms the floor of the cave are the clear impressions of a child’s footprints. He or she, let us say he, was about eight years old. What he was doing that far back in the pitch-black cavern we can only imagine. From the measurements of his gait he was walking quite normally, not running nor hesitating on his way to the back of the cave. Human footprints of this age are very rare indeed, but it is not the track of the boy that makes this so unusual and important for our story. Alongside the child’s is another, quite different, set of prints. Perfectly preserved in the limey sediment that covers the cave floor, hidden from view and undisturbed for 30,000 years, are the tracks of a fully-grown wolf.

We cannot be sure that the boy and the wolf were walking side by side when they made the tracks or whether the prints were left thousands of years apart. The passage is very narrow at this point and yet the tracks never cross each other, making it more than likely that they were made at the same time. Was the wolf hunting the boy? Or were they exploring the cave together, companions in a great adventure? The footprints hint at a very close relationship, friendship even, between the boy and the wolf.

Or was the animal that trotted comfortably at the boy’s side no longer a wolf, but already on its way to becoming a dog?

* This is the ‘Cave of Forgotten Dreams’ of the chapter title. I have taken the name from Werner Herzog’s excellent 2010 documentary film about Chauvet cave.


Hunting with Wolves

The great changes that swept through Europe in the Upper Palaeolithic were products of the refreshed human mind, capable not only of great innovation but also of seeing the world in a different way. An essential element in this process was our ability to learn from observation, to reproduce novelties whenever we saw them. This ability is still with us today, aided by language and other forms of communication. Nowadays new ideas spread around the world almost instantaneously. Even though in the distant past the diffusion of ideas would have been much slower than this, invention and creativity were a characteristic of the time. Whether it be the best way to make an arrowhead or a spear-thrower, or the method of threading beads to make a necklace, or how to make a primitive flute by drilling holes in the wing bone of a swan, all these ideas spread through observation and duplication.

The observant Palaeolithic hunter would have seen wolves in action, relentlessly pursuing their prey until the hunted beast was exhausted, then surrounding it. Unable to inflict a fatal bite through the spinal cord like a lion, the wolf must lunge to inflict flesh wounds until, at last, the animal collapses through loss of blood. It is not a pretty sight as, more often than not, the animal is disembowelled while still alive. More to the point, the endgame is dangerous for the wolves, who risk injury from the last desperate thrashings of their dying prey.

Our ancestors would have witnessed this drawn-out death struggle and realised how easily they could have killed the cornered beast. A spear thrown from a safe distance at an animal held at bay by a wolf pack would be an easy kill. The remarkable stamina of the wolf pack could run down the swiftest prey. By comparison human hunters were no match in the pursuit, but with spears, bows and arrows they could kill even the largest animal cornered by wolves with little risk of injury to themselves.

No doubt at first the final act would seem to the wolves like yet another theft of a kill. Wolves have always been vulnerable to having their kills taken over by more dominant predators. Their ability to rapidly consume, or ‘wolf down’, the nourishing internal organs like the heart and liver, and then to quickly carve off huge chunks of meat using their razor-sharp carnassial teeth, was an ancient adaptation to minimise loss.

In such a situation, it is only a small step for a human hunter to realise how to pacify the wolves. Sharing the carcass is all that is needed. Cooperative hunting is of obvious benefit to both sides, if only the wolves themselves could appreciate the benefit of the deal. This approach would not work with lions or bears, but wolves hunted very much as we did, cooperatively in small groups with each member having a separate role.

There is precious little evidence to support my proposition of a working alliance between man and wolf. It makes a great deal of sense to join forces with a wolf pack in the pursuit of sustenance, so it is a reasonable and attractive speculation, but I freely admit that it is the product of my imagination. I felt nervous about proposing it until I discovered that the great zoologist Konrad Lorenz had already envisaged a similar scenario. In his charming book Man Meets Dog, Lorenz writes a fictional account of cooperative hunting between humans and a pack of jackals, which he saw as the wild ancestor of modern dogs.1 He was mistaken about the jackal, as we now know, but he could equally have chosen the wolf. In 2015, the archaeologist Pat Shipman proposed that a hunting alliance between man and wolf was a major factor contributing to the extinction of the Neanderthals.2

I much prefer this explanation, of hunting cooperation leading to trust, for the origin of ‘domestication’ to the alternatives. Foremost among these, and the one most geneticists seem to prefer (even though I suspect many of them have never seen a wolf), is that wolves became accustomed to human company by hanging around their camps and picking up scraps of food from rubbish tips. As well as being dreary in the extreme, this explanation falls down simply because ‘domestication’ was already well under way by the time humans congregated in large enough settlements to produce sufficient waste to sustain an animal with the appetite of a wolf. Nor does it explain why, of all animals including coyotes, jackals, badgers and bears capable of surviving on refuse, none ever developed a bond of the strength and depth that comes close to matching that between human and wolf – in its modern incarnation, the dog.

Almost nothing remains of human activity on the open plains, so evidence of cooperative hunting is always going to be hard to find. Only in the dank recesses of subterranean caverns can we find physical evidence of our distant ancestry. At Chauvet it is not bones nor teeth but paintings and those enigmatic footprints that are the lens through which we glimpse the lives of our ancestors. Eight hundred kilometres north of