After years of work in the lab, in the field, and on our televisions, noted academic, writer, and broadcaster Alice Roberts has introduced the world to many topics.
Now, as part of Oxford University’s online student gateway webinar series, Roberts has explained how Stone Age hunters domesticated dogs and cattle, how Bronze Age nomads domesticated horses, and how teaming up with these other species helped our ancestors to survive and thrive.
She showed how archaeology and history mesh with genetics to allow us to explore Neolithic life and its legacy.
Roberts is interested in the intersection between biology, archaeology, and history, and the interaction between humans and the environment through time. She has presented more than 100 television programs, on subjects that include biology, archaeology, and history.
When our ancestors tamed animals
For hundreds of thousands of years, our ancestors depended on wild plants and animals. They were hunter-gatherers–consummate survival experts. Then a revolution happened: Our ancestors’ relationship with other species changed as they began to tame them. The result was a boom in human population.
If you ask most people, the most important revolution that humanity has undergone is the Industrial Revolution. However, according to Roberts, an earlier revolution is more crucial to our evolution.
“For hundreds of thousands of years our ancestors lived in a world where they depended on wild plants and animals. They were hunter-gatherers. They were consummate survival experts [and] they took the world as they found it. Then everything changed,” explained Roberts.
The story of human history itself is contingent on what happened next; how humans found allies to accompany us on our evolutionary journey. The fact that dogs, cattle, and horses became part of our extended family changed our history.
Dogs: Our first ally
Even before agriculture began to take root in the Neolithic Age, humans already had made our first ally from among the animal kingdom. Dogs.
“Our modern dogs have all come from European grey wolves. The Jack Russell shares over 99.5 per cent of its genetic sequence with European grey wolves. Darwin was fascinated by dogs and when he wrote On the Origin of Species. He actually opens his book by discussing what he calls artificial selection. In other words, the ability of humans to shape other species by selective breeding,” said Roberts.
Today, after centuries of selective breeding, we have a variety of dogs. But how did wolves first come to our side?
According to Roberts, archaeologists have, in the past, suggested that this domestication was somehow linked to the beginning of farming when people began living in villages and settlements for the first time.
The theory is that middens on the edges of these villages would tempt wolves from the vicinity to approach the settlement. It is logical that, as those wolves became comfortable approaching the human settlement, they eventually would become domesticated. Roberts, however, disagrees.
“The earliest evidence that we have of farming goes back to about 11,000 years ago, and it starts in the Middle East, and also in the Far East as well,” she said. “Dog bones have been found at much, much older archaeological sites. There’s plenty of evidence of dog bones from archaeological sites going back to 14,000 years ago.”
It’s important to note that, according to Roberts, these bones clearly are dog bones and not wolf bones. They also turn up at archaeological sites in Europe, Asia, and North America.
She does admit, however, that the further you go back in time, the harder it gets to differentiate between the two sets of bones.
“We don’t get sudden jumps in evolution in that way,” said Roberts.
It takes a study of the genetics to show the difference.
In 2002 a paper published in the journal Science by a group of Swedish and Chinese geneticists showed the results of DNA samples taken from 654 dogs in Asia, Europe, Africa, and North America over a two-year period.
Peter Savolainen of the Royal Institute of Technology and Zhang Yaping, a researcher with the program at the Kunming Institute of Zoology under the Chinese Academy of Sciences, looked at the differences between the DNA of dogs and that of wolves. The finding for the latest timing of the changeover was interesting indeed.
Domesticated dogs found 40,000 years ago
“We think it’s about 15,000 years ago, so this [paper] looked great because it married up really nicely with the archaeological record,” said Roberts. “In that same paper, those scientists actually said it could be 15,000 years ago, but it could also be 30,000 to 40,000 years ago.”
Savolainen and Zhang’s team focused on stretches of DNA from the cells’ mitochondria, which passes from the mother to its offspring. Based on similarities in that genetic material, 95 per cent of the sampled dogs had come from just three lineages in East Asia.
A second international research team investigated whether dogs in America became domesticated from wolves on that continent or whether the two groups were related.
Researchers at UCLA compared the DNA sequences of New and Old World dogs, including some Latin American and Alaskan dogs that pre-dated European colonization.
This study showed that these DNA sequences indicated that all the dogs share a common ancestor. However, a certain cluster of sequences from ancient Latin-American dogs did not match any modern dogs, indicating that these dogs weren’t used to create modern breeds.
“I think the earlier date was viewed with some skepticism,” said Roberts.
But at least the geneticists had helped move the needle.
“When they started looking at nuclear DNA, an earlier date started to look more likely,” explained Roberts. “The first genome, the first draft genome of the domestic dog, was published in the journal Nature in 2005 and it proved that the dog was most closely related to the European grey wolf.”
According to Roberts, these early dates–especially the earliest possible date of 40,000 years ago, pushed the archaeology, paleontology, and paleozoology communities to reexamine existing finds.
“One team went back to look at archival material, items, objects, and skulls that already had been dug up at various archaeological sites and had been sitting on shelves in museums,” said Roberts.
They used radiocarbon dating to examine nine canid skulls found at sites in Belgium, Ukraine, and Russia dating between 10,000 and 36,000 years ago. Skull measurements also were taken and compared with a recent sample of more modern dogs and wolves.
“What they found was that in that sample of nine skulls, five of them appeared to be quite comfortably wolf, one was impossible to pin down, and three of them were closer to dog than wolf,” she said.
For this sample range of between 10,000 and 36,000 years ago, two of the dog-like skulls were around 10,000 years old, but one was older. The oldest skull in the sample was about 36,000 years old.
Goyet Cave reveals Ice Age treasure
“The Goyet Cave in Belgium is a complete treasure trove of Ice Age artifacts, including all sorts of objects like shell necklaces and a bone harpoon, as well as bones from lots of animals: mammoths, red deer, cave lions, and a large canid that starts to look very much like a dog,” said Roberts.
While a single find may be an aberration, the fact that more ancient dog skulls have been found helps make the case for an earlier date. In Razboinichya Cave in the southern Siberian Altai Mountain range, for example, another skull has been found that dates to 33,000 years ago.
According to the researchers, the Razboinichya Cave specimen appeared to be part of wolf domestication that was disrupted by the climatic and cultural changes associated with the last glacial maximum (LGM). When combined with the Goyet skull, found thousands of kilometers away, it suggests that dog domestication also was multiregional.
“You’re not going to see that there’s a massive change globally overnight in all these different anatomical features,” explained Roberts. “You’re going to see that they change gradually over time.”
Still, with only two examples. It was hard to make a case. Geneticists tended to place the date of domestication in a later period (around 10,000 years ago) and that the dates of 30,000 to 40,000 years ago possibly was a red herring.
DNA sequencing shows ancient dates possible
In June 2015 scientists performed an extraction and DNA sequencing on a rib bone of a 35,000-year-old wolf. When compared to the DNA of a modern wolf, the scientists were able to track the mutation that has occurred in the species over time.
This mutation rate even deviated from the accepted rate … it was slower by about 60 per cent, which made the dog/wolf split genetically possible 30,000 to 40,000 years ago.
Evidence of interbreeding
Another variable that pushed the dog/wolf split back in time was a longer period of interbreeding between the two sets than previously thought.
“We need to completely get away from the idea that once species diverge, that they isolate from each other very quickly,” said Roberts. “In fact, what you get is interbreeding carrying on as long as they’re still compatible with each other.”
What the animal skulls found in Goyet and in Razboinichya show is something unusual. The mitochondrial DNA itself looks unusual, suggesting that it’s possible that the Goyet and Razboinichya animals were distinct from both wolves and dogs.
We were left wondering what goyet really was. Is it an early experiment in domestication that led nowhere?— Alice Roberts
“We are then left wondering what Goyet really was. Is it an early experiment in domestication that led nowhere?” Roberts posited.
A sophisticated 3D analysis of the Goyet skull’s shape published in 2015 revealed that it looks more wolf-like than dog-like. So maybe it is just an odd-shaped wolf. The Razboinichya animal, on the other hand, still appears to fit nicely in the dog camp, especially with its mitochondrial DNA, which still is present in today’s dogs.
Who trained who?
There is enough evidence that early humans used early dogs, but what was the relationship like?
“It may have started as a very gentle symbiosis,” said Roberts, “maybe a kind of loose partnership based on mutual benefit. When we think about the origins of domesticated animals, we often assume that humans are in control and that humans are making choices. But I think it’s actually very likely that in this case, it was the wolves that were essentially making the choices.”
Roberts doesn’t see some kind of canine master plan, just opportunity and time.
“It’s just the fact that you’ve got these two species living alongside each other, and I think there’s a grain of truth in that idea that the archaeologists had about wolves being drawn to middens, even though they were discussing it in the context of Neolithic farming settlements,” she said. “If you look at nomadic camps, there’s plenty of food left around the camp, like discarded carcasses. There is plenty for wolves to eat, and you can just imagine those wolves coming out of the forest in the night to do just that.”
It’s not a giant leap to get from this informal, side-by-side living arrangement between humans and wolves to one that surpasses simple toleration and becomes encouragement.
“The wolves clearly had something to offer in exchange for food, and I think that something may be quite obvious,” said Roberts. “If you team up with another predator, you are going to form a really, really formidable team. So we can imagine these humans with their early dogs being absolutely formidable predators.”
But it wasn’t just hunting that these wolves-turned-dogs provided to early humans.
“I do think we miss out on something if we just focus on nutrition because there’s something that’s rarely mentioned in theories of domestication,” explained Roberts. “Maybe it seems too frivolous, but it’s hard to imagine it didn’t play a role, and that is companionship. If you have a dog, or if you’ve ever had a dog, then you will know about that intense bond and companionship and the fun that comes with having a dog.”
We know early humans had to eat. So do we. But they also had to have fun.
They’re like us.
“I don’t think it’s inconceivable that some Ice Age parent would have capitulated to the same kind of pressure. We’ve spent a long time with dogs. It’s a great story,” she said.