Pets have been changing the course of human evolution for 50,000 years

14,000 years ago: recent analysis suggests a grave in Bonn, Germany containing a man, woman and puppy may be the earliest evidence of emotional attachment to a pet

10,000 years ago: cats finally start catching up with dogs, beginning the domestication process in the Middle East. But cats are still harder to train, which is why Street Cat Bob’s high-fiving is so impressive.

Dogs are not only the objects of our affection. As the first animals ever to be domesticated, they also hold the key as to how the human race began to adapt wild animals for its own use.It is unlikely that wolves could ever have been tamed unless those early dogs had been loved by their owners. First, there would have been no way their owners could have stopped those early dogs from mating with their wild cousins still living nearby, diluting the genes for “tameness” they carried and thus slowing the process of domestication to a crawl – or even reversing it. Second, in periods of famine the dogs might have left of their own accord to find food, or even been used for food themselves (we know that dogs were regularly eaten in prehistoric times). Either way, the “tame” genes that suited these dogs for life with people would have been lost, and domestication would have had to start again from scratch, when better times came along.

However, if these early dogs had been treated like we treat our pets today, they would have stood a good chance of becoming friendlier and friendlier with each generation. If dogs had shared their humans’ sleeping quarters, whether that be a cave or a temporary hut, their wild counterparts would have stayed away, so preventing interbreeding. Dogs given special social status, as some hunter-gatherers afford their pets even today, would have ensured that some food was kept for them even in times of hunger, and prevented their consumption as food. Kept isolated in this way, the newly semi-domesticated dogs would have evolved away from their ancestors’ wild ways, and become the affectionate and trainable companions we know today.

These early dogs may even have changed the course of human evolution. Innovative methods of hunting, using packs of dogs, made it possible for our ancestors to exploit larger prey, such as mammoths and rhinos. So successful were they that these giant mammals rapidly went extinct, and smaller prey such as antelope became scarce. Hunting became less profitable, so paving the way for the invention of agriculture.

Many of our other domestic animals probably also began their existence as pets. The DNA of today’s domestic stock reveals that most separated from their wild counterparts between 10,000 and 5,000 years ago: just as with dogs, it is not easy to see how this could have been achieved, if these cats, cattle, pigs and so on had been treated as mere possessions. The technologies available would have been inadequate to prevent unwanted interbreeding of domestic and wild stock, and famine would have encouraged wholesale slaughter – only much-loved individuals could have survived to give rise to today’s familiar farmyard animals.

The urge to bring animals into our homes is so widespread that it’s tempting to think of it as a universal feature of human nature, but there are plenty of people who feel no particular affinity for animals, whether pets or not. The pet-keeping habit often runs in families: this was once put down to children imitating their parents’ lifestyles, but recent research has shown that it has a genetic basis. Some people, whatever their upbringing, seem predisposed to seek out the company of animals, others less so. Thus the genes that promote pet-keeping may be unique to humans, but they are not universal, suggesting that in the past some societies or individuals – but not all – thrived due to an instinctive rapport with animals.

The very same genes which today predispose some people to take on their first puppy would have spread among the early farmers. Families which included animal empathisers would have flourished at the expense of those without, who would have had to continue to rely on hunting (without dogs) to obtain meat. Why doesn’t everyone carry the genes that make them feel love for animals? Because at some point in history the alternative strategies of stealing domestic animals or enslaving their human carers became successful, as shown by the millions of males in the world today who can trace their ancestry back to Genghis Khan, or the Irish warlords of the Uí Néill clan. But even if you happen to be one of these, that doesn’t necessarily mean you won’t have a dog – you might have inherited your pet-loving genes from your mother!

The Animals Among Us by John Bradshaw is out now (Penguin, £9.99)