From pets at play to the evolution of man

MY dog is like a canine Peter Pan.

He’s six or seven years old — I don’t know his age exactly as he had several previous owners — but that is respectable middle age for a dog. Yet he still behaves like a puppy — he refuses to take life seriously, everything revolves around play.

Retaining juvenile characteristics into adult life is called neoteny by biologists and it’s an interesting subject which seems to be a significant force in evolution.

Actually all dogs are neotenous. They are all descended from wolves but only wolf puppies bark, adults never do, though most dogs bark until their dying day. My dog also has floppy ears and a fawning attitude — two other characteristics of wolf puppies. There seems to be something about domestication which retains infantile characteristics into adulthood. Some toy dog and lapdog breeds even retain foetal characteristics.

There is a classic experiment that documents this process. In Siberia workers in the fur farm industry took wild silver foxes and for 60 years bred them to select for friendliness to human beings — in other words, they domesticated them. Over this period increasing numbers of the foxes started retaining the characteristics of fox cubs into maturity. They developed shortened faces, floppy ears and curly tails.

Similar things occur all over the natural world. Flightless birds have a tendency to resemble newly-hatched chicks. Think of an ostrich. Some of the most obvious examples are among the amphibians. There are several species and races that never grow up but the best known is the axolotl (below) — a tadpole that never turns into a salamander. It reaches sexual maturity and then dies in its ‘larval’ stage, breathing with gills and swimming in water.

But the importance of neoteny in evolution is most apparent in one species — Homo sapiens. We retain a large number of physical and behavioural traits of immature great apes and this may explain why we are so successful.

We have large heads, relatively hairless bodies and many of us have a lactose tolerance that allows us to drink milk as adults. We are also incredibly slow to mature, continuing to develop and learn for the best part of 20 years. Louis Bolk concluded: “Man, in his bodily development, is a primate foetus that has become sexually mature.”

The ability to continue to learn for a great number of years has obvious evolutionary advantages — you get to be a smarter species. But the advantages of a large head, hairless body and the ability to drink milk are not so obvious. One researcher has come up with an ingenious, though possibly far-fetched, theory.

It suggests that at certain critical points in our pre-history we were in conflict with other hominid species. Neanderthals were particularly formidable rivals. They were superior to us in almost every respect, including brain size. But this theory suggests that we developed a cute, baby-like appearance to divert their aggression and then, rather sneakily, overcame them.

That may or may not be how it happened but there is little doubt that reverting to juvenile appearance and behaviour can sometimes be a very effective ploy in evolution. The survival of the fittest can mean the survival of the most immature.

To get back to my dog, wolves have been extinct in Ireland for about 250 years and are endangered in most other countries. But dogs, with their engaging wolf-puppy antics, are doing very well. Is there a lesson in this? Does the human race, if it wishes to survive, have to learn to be more childish?

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