[Via Grasping Reality with Both Hands: Economist Brad DeLong’s Fair, Balanced, and Reality-Based Semi-Daily Journal]
From Underbelly:Underbelly: The Luckiest Horse in the Fifth Millennium BCE: The subject for the day is the domestication of the horse, where and when and how and why, as recounted by David W. Anthony in his fascinating and absorbing new book, The Horse, the Wheel, and Language (2008)—and also a salute to the luckiest horse.in the Fifth Millennium BCE.
Per Anthony, the date is about 4800 BCE; the place is in what he chooses to call “the Pontic-Caspian steppes,” just above the Caspian Sea. The “why” is interesting: apparently not for riding, but for food—horses were big and meaty and could live over the winter in cold climates (riding came later).
AS to “how,” the flip answer is “it wasn’t easy,” which is not surprising when you stop to think of it: horses—or, more precisely, stallions—are a notoriously tricky lot and they wouldn’t take kindly to being stabled or hobbled or slapped into harness.
This sounds like a very interesting story. Being able to track male and female lines of horses has turned up some unexpected facts.
But as to precisely how, the DNA evidence provides a remarkable clue. Per Anthony:
the female bloodline of modern domesticated horses shows extreme diversity. Traits inherited through the mitochondrial DNA, which passes unchanged from mother to daughter, show that this part of the bloodline is so diverse that at least seventy-seven ancestral mares, grouped into seventeen phlogenetic branches, are required to account for the genetic variety in modern populations around the globe. Wild mares must have been taken into domestic horse herds in many different places at different times. (196)
So much for the ladies. What of the gents? Anthony continues:
Meanwhle the male aspect of modern horse DNA, which is passed unchanged on the Y chromosome from sire to colt, shows remarkable homogeneity. It is possible that just a single wild stallion was domesticated. (Id.)
So humans actually were a part of the environment that selected for a a certain trait and allowed those particular genes to be passed down. The only thing I would like to see, and perhaps the book discussses it, is what the genetic makeup of wild horses looks like. Do the male lines show as great a diversity as the female lines? Or are many of the wild horses seen today descended from escaped domesticated horses? Was there ever real diversity in the stallions seen 5000 years ago?
Got the picture yet? “The standard feral horse band,” explains Anthony, “consists of a stallion with a harem of two to seven mares and their immature offspring.”
Mares are…instinctively disposed to accept the dominance of others, whether dominant mares, stallions—or humans. Stallions are headstrong and violent, and are instinctively disposed to challenge authority by biting and kicking. … [A] relatively docile and controllable stallion was an unusual individual—and one that had little hope of reproducing in the wild. Horse domestication might have depended on a lucky coincidence: the appearance of a relatively manageable and docile male in a place where humans could use him as a breeder of a domesticated bloodline. From the horse’s perspective, humans were the only way he could get a girl. From the human perspective, he was the only sire they wanted.
Of course, we see a similar thing when we have looked at dogs. It turns out that many dogs carry genes that make them small, compared to their nearest cousins. It is very likely that the first canine that was domesticated bore this gene, making it much easier for us to tame them. A gene that would have been detrimental in the normal environment became a big plus.