Lewis Wolpert: 'When humans walked across the Bering Strait to the New World 12,000 years ago, dogs walked with them'

Ignore claims that, with the sequencing of the mouse genome, it is they and not dogs who are man's best friends. I love dogs and, as a child, mine was my best friend. They are a truly remarkable group – just consider that the greyhound, the terrier and the St Bernard all come from the same stock, a stock that has its origins millennia ago, when humans took primitive wolves and befriended them. They have been part of human life longer than any other domesticated animals.

How is it that they alone have evolved to have such special social skills? One theory is that early humans raised wolf puppies and selected the most docile offspring. There is also the possibility that some became less fearful of humans and fed off their leftovers, and so survived the best, and may even have lived among their feeders. These early dogs also acquired the ability to read human behaviour – an advantage in relation to being looked after.

They do indeed have cognitive skills that are not found in our closer primate relatives such as chimpanzees. For example, they understand pointing, which primates do not. If food is hidden in one of two containers and the researcher points at one of them, chimps don't understand where the food is, but dogs get it right almost every time.

This ability is inborn, not learnt, as shown by experiments in which some puppies were raised only with dogs, and so had little experience of humans. These did just as well in the test as those raised with people. There is still controversy about this, but there is no doubt that some behavioural characteristics are genetically determined – the collie's ability to herd, for example.

When did all this begin? It's a mystery. An important finding was made in Israel, where a woman had been buried with what was believed to be her puppy, 12,000 years ago. And nearby, a man was found buried with two small dog-like animals. A more scientific approach involved looking at the DNA of the mitochondria of a wide variety of dogs, as well as wolves, coyotes and jackals.

Mitochondria are structures in cells that produce all the energy for the cell and have their own DNA code for some of their proteins. But more important for the study of relationships and evolutionary history is that mitochondria are all inherited from the female's egg – the male contributes nothing. This makes looking at relationships much easier.

The conclusion from these analyses is that dogs arose some 135,000 years ago. But other scientists disagree and say that it was around 25,000 years ago. There is agreement, however, that when humans walked across the Bering Strait to the New World more than 12,000 years ago, dogs walked with them.

The variety of dogs is a wonderful example of evolution in action. No matter how long it took, selection for different behaviours by humans resulted in Pekinese and borzois. It illustrates nicely how selection for small differences in, for example, the length of snout can result in the poodle or the greyhound. I love dogs and identify with them. It would not surprise me if it were shown that people do choose dogs that they resemble. My granddaughter wrote a story at school about a man who thought he was a dog – she was thinking of me.

Lewis Wolpert is professor of biology as applied to medicine at UCL