Dogs may have been a better friend to humanity than we ever realized, according to an article by Dr. Pat Shipman in American Scientist. They may have played a crucial role in helping modern humans outcompete our Neanderthal cousins.
Many theories have been proposed for why Neanderthals couldn't seem to compete with the invaders, when modern humans arrived in Europe some 35-45,000 years ago, including climate change, the newcomers' better social organization, or their greater facility for language. But new lines of evidence are beginning to suggest another possibility: that it might have been the domesticated dog that gave H. sapiens sapiens the edge over Neanderthals (and, one must presume, Denisovans). There's now mounting evidence that modern humans were domesticating dogs by 35,000 years ago, during the same period when modern human populations began to increase and Neanderthal populations were in decline. Dogs were used for hunting and as pack animals, as they are used even into modern times by some groups. Studies reveal that dogs can significantly increase the success of a hunt and the amount of meat brought in to a community who uses them.
If the dogs carried the meat, humans would have saved a lot of energy, so each kill would have provided a greater net gain in food—even after feeding the dogs. Additional food generally has marked effects on the health of a group. Better-fed females can have more babies, can provide them with more milk and can have babies at shorter intervals. Before long, using pack dogs could have caused the human population to increase.
Dogs may also have contributed more directly to human hunting success. To discover how big a difference dogs could make, Vesa Ruusila and Mauri Pesonen of the Finnish Game and Fisheries Institute investigated what may be the closest easily studied analog to a mammoth hunt: the Finnish moose hunt. Finns use large dogs such as Norwegian elkhounds or Finnish spitzes to find moose and keep them in place by barking until humans can approach and shoot them. In hunting groups of fewer than 10 people, the average carcass weight per hunter without dogs was 8.4 kilograms per day. With dogs, the yield went up to 13.1 kilograms per hunter per day—an increase of 56 percent.
Shipman reminds us, too, that domestication is a two-way street: as dogs were selected to communicate better with humans, there might have been selective pressure making humans also better able to communicate with dogs. Interestingly, humans have a unique feature among living primates, which might have aided in our domestication of canids: the whites of our eyes.
The mutation causing white sclerae is universal in humans, but it turns up occasionally in apes, too. In decades of observations at Gombe National Park in Tanzania, Jane Goodall observed two chimps, probably brothers, who had white sclerae. A third, female chimp developed white sclerae as an adult. But the trait has not spread or reappeared in that population. The advantage of the white sclerae must be related to something that ancient humans did commonly and chimps don’t do or do rarely. Although chimps hunt small prey, often cooperatively, meat makes up less than 2 percent of their diet, whereas Paleolithic humans hunted much larger game that apparently provided a significant part of their diet. Obviously, silent communication among humans would be advantageous for hunting in groups. But there is another skilled gaze-reader: the domestic dog.
A dog will follow the gaze of a videotaped human if the human first attracts the dog’s attention by speaking to it and looking at it, according to results published by Ernõ Téglás, of the Central European University in Budapest, Hungary, and his colleagues. Indeed, dogs perform as well as human infants at following the gaze of a speaker in tests in which the speaker’s head is held still.
But why didn't Neanderthals domesticate dogs? We might wonder. Could it be that, like other extant primates, they also didn't have visible sclerae, putting them at a disadvantage with the wolves?