The story of how the dog got domesticated is literally a puzzle of missing pieces which ever so slowly is gradually becoming complete. Popular lore of how the dog became domesticated holds that as humans evolved from the Paleolithic period (during which time man captured his prey using axes and heavy stones) to the Mesolithic period (when the use of stone-blade tipped arrows became widespread) they began using dogs to hunt down their prey which they killed off with their newly devised weaponry.
Indeed firm archaeological evidence puts the dog as the first species of animal to have ever been domesticated, around the tail end of the last Ice Age when human subsistence still revolved around the hunter-gathering system. Presently the earliest evidence pointing to the domestication of the dog consists of a mandible found in a grave at Oberkassel in Germany dating back to the late Paleolithic period (approximately 14,000 years ago).
Such evidence though does not explain how the dog came into being as a species or how the long lasting relationship between dog and man evolved.
Man Tames The Wolf…maybe!
As far back as the Middle Pleistocene period wolf bones have been discovered in association with those of early hominids. Some examples include the 400,000 year old site of Boxgrove in Kent, England; the 300,000 year old Zhoukoudian site in North China; and the 150,000 year old cave of Lazeret located near Nice (southern France). Those commingled human and wolf fossils indicate that hominid populations of the time must have overlapped wolf territories. Humans probably killed wolves as a food source and also to use the wolf skin/furs as clothing.
Perhaps, on occasion, a wolf pup was adopted as a pet or companion. Could such “tamed” wolves have indeed been the precursor of the dog and could this have truly been the means by which the modern dog first evolved? Remains of these “tamed” wolves have been described from sites located in Central Europe and interestingly enough they exhibit morphological differences from those of wild wolves. The so-called tamed wolf was characteristically smaller in size, had a shortened facial region, compacted teeth and toe bones that were more slender than those of the average wolf.
A comparison of the head size of a dog weighing approximately 100 lbs (average weight of a mature wolf) with that of a wolf amply illustrates that the head of the dog is about 20% smaller. For a dog skull to approximate the same skull size as that of the average wolf, the dog would necessarily have to be one of the larger breeds (wolfhound) and that dog would have to weigh anywhere between 150-180 lbs. Curiously though the brain size of that dog (which outweighs the wolf by 50-80 lbs) is 10% smaller than the wolf’s!
Process Of Domestication
Characteristics that are extremely valuable for survival in the wild are by their very nature an impediment to domestication. Such characteristics include large size, wariness, big brain size and independence. In other words those features that jeopardize survival in the wild (lack of fear, high tolerance to stress, decreased intelligence and docility) are conversely highly desirable traits in domesticated animals. This makes a lot of sense because humans domesticate animals to do their bidding and a willful, overly intelligent independent animal would have a hard time existing within such confines.
The biological process of domestication closely resembles natural evolution by the manner in which a reproductive population of animals becomes isolated from the rest of the wild population and inbreeds within the confines of the separated group. Initially this “source group” of animals would be largely inbred but as their numbers multiplied the genetic pool would become more diverse and varied in response to their new environment, which in the case of the tamed wolves, would be an environment that revolved around humans.
It is postulated that the reduction in size of the wolf during domestication was due to the fact those initial tamed individuals were not fed sufficient quantities of food to attain the natural full size they would have otherwise attained in the wild. This scenario appears quite appealing especially when one takes into account that those wolves were tamed by hunter-gathering societies. It is natural to assume that the people would satiate themselves first before feeding their wolf pets scraps and any leftovers.
Smaller sized wolves, in an opposite scenario to that found in the wild, would have been better adapted to survive in captivity because of their diminished feeding requirements. It is even possible that their human caretakers perhaps drove off or more likely killed the larger individuals because of their high maintenance cost! As for the reduction in skull size, teeth size and brain those would have occurred naturally over time through hormonal changes in response to the requirements of the new environment. The shrinking head size would have come about due to the reduction in brain size which would have happened because a large brain requires more calories and was no longer warranted.
Other traits, which though highly valuable for survival in the wild but no longer useful in the tamed animal would also have been lost somewhere along the line, included acute hearing and vision and a hyper alertness to the wolves environment.
The above description for how the domestication of the dog came about seems very plausible except for one rather gaping flaw…
Tamed Wolves Do Not Produce Tame Offspring!
It seems very unlikely that the humans of 15,000 years ago (Mesolithic period; the time when it is believed dogs truly came into being) had the time or the intelligence to invest in a selective breeding program that aimed for a tamer wolf! The people of that period would have been too busy grappling with the basics of everyday survival: finding food, keeping warm and keeping safe. And on the rather implausible chance that they did have both the time and smarts to invest in such a breeding program there is not a shred of evidence that supports the likelihood that those people had a large enough tame-wolf population to embark on such a program.
Furthermore those folks would have had another problem on their hands; the fact that taming an individual animal does not automatically result in tame offspring even over a span of several generations. Modern day wolf researchers are well aware that tame wolves behave nothing like dogs and retain many of the characteristics undesirable in a domesticated animal; namely independence and wariness of people.
When a tame wolf gives birth, it produces naturally wild offspring which is in stark contrast to the offspring of dogs which are inherently tame right from the get go! If a wolf pup from a tamed individual is not socialized by humans before its eyes open that animal will have problems dealing with people; the same is not true of dogs even for much older puppies of several months! In other words, the taming of individual animals does not bestow genetic modification upon its offspring even over a span of many generations. Simply put, the idea that people from the Mesolithic period tamed the wolf and gradually transformed it into the domesticated dog seems to rest on very shaky ground indeed!
The Wolf Tamed Itself Into The Dog!
Instinctive as it is to assume that humanity tamed the wolf eventually into the domesticated dog, perhaps there is an alternative and somewhat more credible scenario…the wolf initiated the process of domestication!
In any population of animals there are always individuals that exhibit anomalous traits not apparent in the majority of the group and of little value or desirable for the survival of the species. Normally such individuals would not survive long in the wild and thus such undesirable traits would not be spread to the rest of the population through reproduction. But sometimes circumstances arise that ensure the continuity of such traits. Perhaps such an undesirable trait in the wolf led to the evolution of the domestic dog.
Around the time of the Mesolithic period is when humanity first started establishing permanent settlements; it is no coincidence that this is also the period that dogs are thought to have first appeared. One result of any area long populated by people is the creation of dump sites. Such a dump site would naturally have attracted animals including wolves which are not above scavenging.
Since even then man hunted wolves, they would have been wary of humans; and therein lies the wolf’s problem as an efficient dump scavenger. The wolf is far too skittish to make an efficient scavenger, running a long distance off at the slightest hint of danger or the approach of anybody. Compounding this skittish nature is the fact that most wolves will take an inordinately long time before daring to venture back to the dump site…all in all a rather inefficient means of feeding.
But just suppose there were certain wolves that didn’t display the usual level of skittishness the other wolves did. Maybe such wolves were less wary because they were driven by a need to sate their hunger. Such wolves would have been smaller than the other individuals in the wolf pack and thus would have been weaker and ranked lowest in the social structure of the pack. This meant they would have eaten last and gotten the least amount of nourishment thereby compounding their relatively small stature. A human dump site would have been especially appealing to such a wolf.
Over time this type of wolf may have dissociated itself from the pack and stuck around the human settlement instead. After all the settlement offered everything necessary for its survival without the wolf pack: a steady food source, relative protection (other animals would have been wary of the location) and comparative shelter.
Gradually such wolves would have become habituated to humans losing all fear of them altogether. The wolf had good reason to lose its fear because humans “ensured” it had a steady supply of food (dumping refuse). Eventually a couple of such wolves would have mated and raised a litter of pups which from an early age would have been in close proximity to people. This would have accounted for the isolation and inbreeding necessary for a species to evolve from another.
In conclusion, the last scenario which hypothesizes the wolf initiated the taming process to eventually evolve into the domestic dog is much more credible than the one which would have us believe that Mesolithic man conducted selective breeding programs to cultivate a tamer wolf; such a supposition would by necessity mean that Mesolithic humans had hundreds of tame wolves with which to select desired traits from!
Article On Dog Domestication by Kayye Nynne