Reference: “Dogs make us human”

But a study by Robert K. Wayne and his colleagues at UCLA of DNA variability in dogs found that dogs had to have diverged from wolves as a separate population 135,000 years ago. The reason the fossil record doesn’t show any dogs with humans before 14,000 years ago is probably that before then people were partnered with wolves, or with wolves that were evolving into dogs. Sure enough, fossil records do show lots of wolf bones close to human bones before 100,000 years ago.

If Dr. Wayne is right, wolves and people were together at the point when homo sapiens had just barely evolved from homo erectus. When wolves and humans first joined together people only had a few rough tools to their name, and they lived in very small nomadic bands that probably weren’t any more socially complicated than a band of chimpanzees…

This means that when wolves and people first started keeping company they were on a lot more equal footing than dogs and people are today. Basically, two different species with complementary skills teamed up together, something that had never happened before and has really never happened since.

Going over all the evidence, a group of Australian anthropologists believes that during all those years when early humans were associating with wolves they learned to act and think like wolves. Wolves hunted in groups; humans didn’t. Wolves had loyal same-sex and nonkin friendships; humans probably didn’t, judging by the lack of same-sex and nonkin friendships in every other primate species today. (The main relationship for chimpanzees is parent-child.) Wolves were highly territorial; humans probably weren’t – again, judging by how nonterritorial all other primates are today.

By the time these early people became truly modern, they had learned to do all these wolfie things. When you think about how different we are from other primates, you see how doglike we are. A lot of the things we do that the other primates don’t are dog things. The Australian group thinks it was the dogs who showed us how.

They take their line of reasoning even further. Wolves, and then dogs, gave early humans a huge survival advantage, they say, by serving as lookouts and guards, and by making it possible for humans to hunt big game in groups instead of hunting small prey as individuals. Given everything wolves did for early man, dogs were probably the big reason why early man survived and Neanderthals didn’t. Neanderthals didn’t have dogs.

But dogs didn’t just help people stay alive long enough to reproduce. Dogs also made it possible for humans to pull ahead of all their primate cousins. Paul Tacon, principal research scientist at the Australian Museum, says that the development of human friendship “was a tremendous survival advantage because that speeds up the exchange of ideas between groups of people.” All cultural evolution is based on cooperation, and humans learned from dogs how to cooperate with people they aren’t related to.

Maybe the most amazing new finding is that wolves didn’t just teach us a lot of useful new behaviors. Wolves probably also changed the structure of our brains. Fossil records show that whenever a species becomes domesticated its brain gets smaller. The horse’s brain shrank by 16 percent; the pig’s brain shrank as much as 34 percent; and the dogs’s brain shrank 10 to 30 percent. This probably happened because once humans started to take care of these animals, they no longer needed various brain functions in order to survive. I don’t know what functions they lost, but I do know all domestic animals have reduced fear and anxiety compared to wild animals.

Now archaeologists have discovered that 10,000 years ago, just at the point when humans began to give their dogs formal burials, the human brain began to shrink, too. It shrank by 10 percent, just like the dog’s brain. And what’s interesting is what part of the human brain shrank. In all of the domestic animals the forebrain, which holds the frontal lobes, and corpus callosum, which is the connecting tissue between the two sides of the brain, shrank. But in humans it was the midbrain, which handles emotions and sensory data, and the olfactory bulbs, which handle smell, that got smaller while the corpus callosum and the forebrain stayed pretty much the same. Dog brains and human brains specialized: humans took over the planning and organizing tasks, and dogs took over the sensory tasks. Dogs and people coevolved and became even better partners, allies, and friends.

Grandin, 304-306 ("Dogs Make us Human," from Geek Buffet)