The idle ramblings of a Jack of some trades, Master of none

Apr 2, 2007

Going to the Dogs

Here's an interesting story. It's widely accepted that dogs evolved from wolves in an evolutionary process taking about 14000 years. But Susan Crockford, an evolutionary biologist at the University of Victoria, claims that this domestication could have taken as little as forty years - well within the lifespan of one human being. She bases her contention on a forty-year experiment by a group of Siberian geneticists, who bred silver foxes for docility. That group, led by Dmitry Belyaev found that within twenty generations - or about twenty years, as foxes breed annually - the appearances of new cubs changed remarkably. Curled tails, drooping ears and piebald markings appeared. Some even began to bark. (It is known that wolf cubs bark, but they tend to lose this ability as they grow older.) Wolves breed every two years, so it is entirely feasible that a similar breeding programme in the wild millennia ago resulted in dogs in as few as four decades.

Crockford says that this timeline would explain the burial of dogs on top of humans in the Americas. The dogs, having seen to have morphed from wolves in a human lifespan, might have given rise to myths of transformation, and assigned supernatural powers. Hence the ritual burials of the dogs in curled positions, as though asleep.

The reason for the rapid domestication of the wolf may have been owing to evolutionary pressures on thyroid production. First of all, only the more docile wolves would have stayed on in human settlements, even if in the first place, low food supplies at the close of the Pleistocene era drove them into the settlements to hunt. Further, the hormone, thyroxin, is known to coordinate growth and behaviour, so selective breeding of the docile wolves by the humans could have resulted in physical and behavioural changes over time.

I guess I should read Crockford's Rhythms of Life: Thyroid Hormone and the Origin of Species to pontificate about this some more. But the precis at this location provides more detail than I really want. And anyway, dogs, wolves, they are all the same to me.


Post a Comment