Best Friends

I am more a cat person than a dog person. Not that I dislike dogs but I just find cats easier to care for and better adapted to a suburban environment. Our three cats come and go as they please through cat doors and, apart from waking us if we oversleep, seldom demand anything more regular feeding and occasional attention, which provides us with pleasure too.

Dogs, however, have a long history with humans.

A recent study traces the domestication of dogs back to about 32,000 years ago in China. In the split from wolves, apparently dogs have developed many adaptations to make them more like humans, including the ability to metabolize foods the wolf cannot and, of course, a better disposition. One theory is that dogs split from wolves when wolves became scavengers around human settlements. The tamer of the wolves became appreciated as watch dogs and the more vicious were killed or run off. Occasionally orphans may have been adopted as pets. Through this inadvertent interaction we domesticated wolves and changed them into dogs.

“The researchers note that scientists have long-held the notion that domestication of dogs and other animals has been associated with people and animals living in close quarters in relatively tight communities. Such conditions, they contend would almost certainly have a similar impact on people as well as the animals living in the same environment. They note that dogs, for example, in addition to exhibiting similar genes, also suffer from many of the same kinds of diseases, e.g. breast cancer, obesity, epilepsy and even obsessive-compulsive disorder.” (1)

What is amazing about this is the relatively quick time period – possibly less than a few thousand years – in which these adaptations occurred. These adaptations must have parallels in human evolution. In our case, however, we domesticated ourselves. I have speculated that the final stages of this transformation from early human to modern human may have occurred in Southern Africa approximately 90-100,000 years ago. During that period, humans may have changed themselves from small pack hunting groups, much like wolves, to larger tribal groups living of people living in close proximity. The demands of close living drove our own self-domestication.

We apparently have something else in common with dogs, possibly as a holdover from our pack hunting days. Dogs like humans experience a runner’s high. Endocannabinoids, chemicals similar to the active ingredients of marijuana, have been found in dogs after aerobic exercise. “A neurobiological reward for endurance exercise may explain why humans and other cursorial mammals habitually engage in aerobic exercise despite the higher associated energy costs and injury risks, and why non-cursorial mammals avoid such locomotor behaviors.” (2) Dogs like us (or some of us at least) enjoy running.

Notes

1- http://phys.org/news/2013-05-dogs-domesticated-earlier-thought.html

2- http://jeb.biologists.org/content/215/8/1331.abstract

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