Our oldest friends in the animal world is the dogs. The relationship goes back as far as 40,000 years by estimation. However, not much is known about how this relationship was built up.
Animals can be described as domesticated when:
- they become genetically different from their wild forebears, and inherit a human-friendly demeanor
- they become dependent on humans for food and reproduction
- breeding with wild counterparts become difficult
- they bear the physical hallmarks of domestication syndrome such as a smaller skulls
Based on these criteria, some people argue that cats are not fully domesticated. They haven't changed much physically or genetically from their ancestors, and they still choose their own mates and hunt for food. Interestingly, on the contrary to cats, some researchers insist that we (humans) have domesticated ourselves. We may have began weeding out people with an overdose of reactive aggression, and selected among themselves for tameness. We share similar physical hallmarks of domestication as other domesticated animals: our faces are shorter with smaller brow ridges, and males' and females look quite similar.
How these process went along was basically a matter of mystery. We only had some archaeological bases, so we just assumed that some people, somewhere, brought wild things under human control. Or the wild creatures exploited new ecological niches created by humans, gradually habituating themselves to people and, in essence, domesticating themselves.
Recent development of genetic science is trying to disentangle some of these mysteries. It is revealing when and where domestication started to take place, and how it spread around the world. For example, it was assumed that people captured just a few stallions and bred them to many different mares. However, recent analysis found a wide variety of Y cromosomes in domesticated horses living 2,500 years ago. This means that there are much more diversity, and many stallions contributed DNA to horses’ gene pool for at least the first few thousand years of domestication. Genetic analysis is also assessing how domestication can be described by changes in the genes.
There might be much more stories coming up in this area in the next few years.