Feeding dogs on the streets may seem second nature to many people now, but millions of years ago, dogs’ ancestors—wolves—and Homo sapiens’ predecessors may have competed for the same kinds of food, living as they did in harsh climates when glaciers covered huge parts of the earth. How then did they learn to live together and share?
That’s the same question that a group of five researchers from Europe, who study Arctic peoples, had. Or as they put it in a paper published on 7 January, “How could humans possibly have domesticated a competitive species?” Both wolves and humans were carnivores, hunted in packs in the same spaces, took down large animals as prey, and were capable of killing each other over food. The difference, the researchers conclude, might lie in the way the two species digested the proteins in the meat they ate.
When resources—in this case, game—are abundant, species share, but in the harshness of the last Ice Age, somewhere between 2.5 million and 11,700 million years ago, it was unlikely. Animal-based diets were more popular, since the cold limited the availability of plants. Humans evolved from gatherers to hunter-gatherers as the climate changed so our bodies are less adept at digesting meat than plants. “Humans are not adapted to a solely carnivorous diet and are only able to digest about 20% of their energy needs from protein,” the scientists write. Wolves, on the other hand, because of their evolutionary history could easily digest all forms of protein. So, the ancient hunters of Eurasia who found the excess protein in their prey a bit hard to digest probably tossed it out to the wolves nearby—and in time, wolves became domesticated.
The researchers, led by Maria Lahtinen of the University of Helsinki, write: “We suggest that the differences between dietary constraints of wolves and humans enabled dog domestication in harsh environments in the Late Pleistocene. Excess protein decreased dietary competition and enhanced the possibility of sympatric existence.” And then, quite charmingly, they add: “This could have been a significant impetus for wolves to become ‘our best friend’.”
Previous theories have suggested that early humans tamed wolves—this isn’t likely the scientists say as its hard to imagine a competing species cooperating with us. The other theory is that they were attracted to waste. The authors dismiss this with, “During the Palaeolithic, it is unlikely that humans occupied sedentary or semi-sedentary sites where substantial amounts of waste could be generated.” Or more simply, we just didn’t stay in one place long enough, have enough resources, or consume enough to generate the monumental amounts of garbage we do today and which many stray animals feed on.
“According to our theory, late Pleistocene hunter-gatherers in Eurasia would have had enough free/excess animal derived calories to feed proto-dogs/captured wolves during lean winter months and therefore humans and canids would not have been in competition over resources. Given that there would not have been competition over resources, even a small benefit from keeping captive wolves, such as hunting aid or protection against predators, would have been advantageous for both species,” the study observes. In other words, food started a friendship that’s lasted across the ages.