Dogs Evolved To Eat Human Scraps As We Started Farming

Domestica dogs can easily digest starch, unlike their wild ancestors. Anneka/Shutterstock

Josh Davis 10 Nov 2016, 16:13

As man’s best friend, dogs are thought to have started hanging around with humans around 15,000 years ago. How this special relationship between two predators first kicked off has been a bit of a mystery, but a new study published this week in Royal Society Open Science may give new hints as to the origins of the domestic dog. It turns out that dogs started evolving the ability to digest starch at around the point humans started farming, suggesting that the mutts may have been scavenging on our scraps.

In all wild species of canine, from jackals to coyotes to wolves, their DNA contains only two copies of the gene involved in starch digestion, known as Amy2B. This is presumably because their diets tend to be rich in protein, supplementing it occasionally with berries and plant material, though how much vegetation they actually consume is still not fully known. This is in stark contrast to domestic dogs, with some breeds found to have up to a whopping 30 copies of Amy2B, giving them the ability to easily digest starch, which is more common in domestic dog diets.

At what point these duplication events occurred has, until now, been unknown. Some have suggested a more recent origin, within the last few hundred years as selective breeding has created most of the shapes and forms of dogs we see now. But this latest study has found a much more ancient origin. Analyzing the DNA from the remains of four dogs that lived between 8,000 and 4,000 years ago in what is now Romania, Turkey, and France, the researchers found that they had already started duplicating the Amy2B gene, and had eight copies of it.

There has been considerable debate as to how, and where, dogs first became domesticated. Some suggest that their wolf ancestors were first recruited by hunter-gatherers to aid in taking down prey, and then benefitted from the spoils left over, while others argue that the animals instead started hanging around human camps eating scraps left behind. This latest study feeds into this discussion, showing that at the same time we began developing agriculture, the dogs’ ancestors were evolving to exploit this new food source.

Interestingly, this duplication of the genes involved in starch digestion is one mirrored by ourselves. During the same period of time that this was occurring in dogs, humans were also acquiring more copies of these genes to help break down a diet becoming increasingly heavy in starch as we developed farming. This indicates that there has been a similar process of evolution between the two species as we shared not only our environment, but also our food.

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