A recent paper on ancient pig genetics got me to thinking about how far back we can trace artificial selection or selective breeding by humans. The selective breeding of plants probably took off only after the last ice age (starting from about 12,000 years ago) when the hunter-gatherers settled down and stayed long enough in one place such that they could actually breed successive generations of plants.
While the systematic breeding of livestock was also surely enabled or enhanced by the conversion to a settled lifestyle, it must have been that hunter-gatherers started herding activities of aurochs or reindeer somewhat earlier in the mesolithic (30,000 to 10,000 years ago). In fact a nomadic life style with a dependence upon a particular species of migrating herd could itself have provided the transition from being completely foot-loose hunter-gatherers to becoming fully-fledged agriculturists. When following and living off wild herds some measure of artificial selection could have been – and probably was – used, though rather by the culling of overly aggressive or weak or handicapped individuals than by the active breeding for selected traits. But the selective breeding for particular traits must already have been known by then. Domestication of some animals occurred long before the last ice-age. And whether by accident or by human design – and probably by both – domestication was itself the exercise of artificial selection.
But which was the first animal that humans domesticated? The list of domesticated animals is long but any evidence prior to the start of settled agriculture is scanty. It is generally thought the first must have been the dog. Initially before DNA there was uncertainty as to whether dogs had genetically derived from jackals or foxes on the one hand or from wolves on the other. But now ” DNA evidence has ruled out any ancestor canine species except the wolf …. Based upon the molecular clock studies conducted, it would seem that dogs separated from the wolf lineage approximately 100,000 years ago. While evidence for fossil dogs lessens considerably beyond 14,000 years ago and ending 33,000 years ago, there are fossils of wolf bones in association with early humans from well beyond 100,000 years ago”. The earliest evidence – so far – of ancestral dogs being associated with humans is from about 32,000 years ago. “The fossil large canid from Goyet (Belgium), dated at c. 31,700 BP is clearly different from the recent wolves, resembling most closely the prehistoric dogs”.
So it would seem that it all started with some form of human – wolf association which was in place by around 100,ooo years ago. It is tempting to think that the wolf – dog divergence which also begins around 100,000 years ago must also be connected with this association. It is plausible that this association was first initiated by the wolves. Already by this time humans were probably among the most successful hunters of the age. It could have begun when a propensity for scavenging behaviour led some wolves to take advantage of first following behind human hunting parties and later to “hanging-out” by human campfires. These wolves then probably had some critical traits which encouraged this behaviour and which were then carried forward to their descendants. This selection for traits encouraging this behaviour may well be the point of divergence of the wolf – dog lines. The closer association with humans and the deliberate manipulation – by culling first and later by selective mating – of the canine line must have come later as humans began to appreciate the advantages provided by these companions. There is evidence that dogs may have been domesticated from wolves on different occasions and at different places and also that domesticated dogs were bred with wolves from time to time. Of course this cross-breeding may not have been instigated by humans, but I suspect that this was in a period where the concept of “domestication of wolves” by selective breeding was itself being disseminated among humans as they spread around the world.
Certainly by 32,000 years ago when ancestral dogs are being buried together with their human “masters” the relationship has developed much further and has become a partnership. It appears that Neanderthals did not have domesticated dogs and the dog-human partnership was created somewhere in the Middle East.
This puts the use of deliberate actions for selective breeding some time after 100,000 years ago and some time earlier than 32,000 years ago. This would have been after the leaving of Africa but before the great expansion of AMH from the Middle East. This leads me to place the earliest deliberate breeding of selected traits – both by culling and by selective mating – in the domestication of dogs at some 50 – 60,000 years ago in the Middle East.