Looking at the selfless love our canine companions often bestow on humanity many people have asked: “What did we do to deserve dogs?” The answer may be not being able to handle a high-protein diet.
Considering the importance of canine companionship to human success, we don’t know much about how it happened. We know that dogs split from their wolf ancestors between 27,000 and 40,000 years ago, and that dogs became domesticated sometime between 18,000 and 30,000 years ago, with the earliest known pet dog burial dated to 14,200 years ago. We don't know whether domestication happened once or twice, though, let alone how we came to love what had once been a rival and threat. After all, even after we had made dogs part of our homes, the “big bad wolf” lurked in our nightmares and fairy tales.
The most popular theories for how canine domestication came about involve cooperative hunting with wolves, or lurking around campfires for waste (them, not us). Dr Maria Lahtinen of the University of Helsinki in Finland points out that the more wolves competed with our ancestors, the less likely we were to tolerate their presence nearby. She sees overlap in diet as the key measure of how strong this competition would have been.
In Scientific Reports, Dr Lahtinen points out all the earliest examples we have of dog burials come from Arctic or sub-Arctic sites towards the end of the last Ice Age. Winters were so fierce at the time humans would have had few plants to supplement meat-rich diets.
Moreover, she notes, the human liver cannot handle a diet too high in protein, a legacy of our herbivorous heritage. In summer with abundant fruits, nuts, and seeds this would not have been a problem, but Lahtinen argues fatty cuts would have been preferred over leaner meat come winter.
Wolves have no such restrictions. Although partial to blueberries in season, they can live on a diet of nothing but protein-rich meat for months if necessary.
Lahtinen looked at the protein content of all species considered to be winter prey in late Ice Age north-central Eurasia. Aside from weasels, all were so protein-rich people would have needed a part-vegetable diet to digest the leanest cuts. Why not give what was left for the wolves?
For some prey, such as adult caribou, the excess protein is small and probably insufficient to form the basis of a lasting relationship. However, rabbits and bison are so protein-rich there would have been plenty to share.
Wolves fed on meat humans didn’t want would have posed less threat to the prey we did, and as time went on the close relationships forged over a carcass made room for companionship and joint hunting. In summer the mixed diet would have allowed humans to eat the leanest cuts, but with abundant food available, it would have been easy to leave some aside for our winter friends.