Dog domestication remains a controversial topic among researchers.
Some facts are becoming clearer, but many theories still exist and much is still to be nailed down. The popular belief for sometime was that early humans stole wolf pups and then these tamer animals became the founding animals for a species that was to become the domestic dog. But researchers today, who work with wolves and who on a regular basis “steal” the wolf pups at 10 days of age – right as the sensitive period for socialisation begins, have found that this is a tricky process and although the pups are heavily socialised with humans, from soon after birth, they in no way end up behaving like dogs as they mature. It is highly unlikely that neolithic humans, some 10 000 years ago, would have had the energy and time to commit to this. Humans today can barely train their much more approachable dogs!
A more robust theory is that some wolves, who began to scavenge from the outskirts of human settlements, as neolithic man moved to living in villages and no longer roamed as a hunter gatherers, managed to survive better and were more likely to reproduce. Being less shy around the humans, who scraps they fed off, gave them a reproductive advantage over their more risk averse counterparts. Over time these less wary wolves may have made phylogenetic leaps (saltations) that saw their morphology change.
So this evolution was a process that occurred without the active input of people, but similar to any other evolutionary process whereby an animal’s morphology and behaviour changes to meet its niche. The new animals were ones that lived on the periphery of human settlements, adding starch to their diet some 10 000 years ago, not fleeing when humans approached, becoming disestrous (coming in to heat twice a year) and no longer cycling according to seasons because of the adequate supply of nutrients. In the same way as we have domestic rats, mice, cockroaches and pigeons – dogs just came to be. We also learned to live around them – we evolved along side.
Wolves (Canis lupus) may have remained wary and untrusting of people, moving away when people were in sight, and the subset of wolves that went on to become dogs (Canis familiaris) became less and less like wolves in behaviour and appearance. This may have occurred in fact quite quickly as the Silver Fox experiments of Balyaev demonstrates. When he began selecting silver foxes for “tameness” ( not moving away from the outstretched hand) – a whole swathe of morphological characteristics followed suit – the foxes began to show floppy ears, paler colours, bark and play more. In a mere twenty generations, by selecting for a single behavioural characteristic and only breeding these animals together, the whole appearance of the tame fox had changed. This model is helpful when when think of how dogs may have come into being.
The vast number of breeds that we have today are not a reflection of natural selection but rather an example of “unnatural” selection that has occurred for the last few hundred years. Their characteristics do not offer a survival advantage if they were to compete for food ( in the maelstrom of a “village”) and reproductive fitness is definitely lacking in some breeds. The mutations (that arise in any population) have produced desirable breeds, such as the chondrodystrophoid ( dwarf ) and the brachycephalic ( flat faced) dogs and are examples of what can happen when a random mutation is maintained and promoted through capricious breeding by people, but their presence is very far from what would happen when village dogs the world over breed without the interference of humans.
The household dog of the Western world makes up a mere 15% of the world wide population of domestic dogs. Village dogs exist much like their ancestors did – scavenging on human detritus – often maligned and considered dangerous and dirty. Their presence might have some impact on reducing waste but they are not working for the humans they surround.
Household dogs differ in that they are more reliant on the humans they live with, but sadly when humans have selected dogs and constructed “modern” breeds they often have done this with little thought of the desirable traits of a modern pet. Instead they may be selecting on colour, genealogy and unhealthy morphologies that humans find attractive ( eg flat faces) but are not conducive to general health. The end result are individuals with a long list of possible hereditary diseases and behavioural abnormalities who we continue to breed and therefore exacerbate the issues further. In our manipulation of the domestic dog we have sometimes created munted animals that really have a limited niche (a caregiver able to afford expensive healthcare) and whose lives are foreshortened by pain and discomfort. We call dogs “man’s best friend” but is our manipulation of them in their and our best interest?
For more reading on this and on domestication and genetics see:
Grandin, T., & Deesing, M. J. (Eds.). (2013). Genetics and the behavior of domestic animals.