Monsters bred for vanity of man

Domestication allows humans to produce animals in colours and shapes that would never survive in the wild. Tim Birkhead argues that it is time for us to put a brake on the process

The issue of genetically engineered pets has exploded into public consciousness. A few weeks ago, we might have smiled at the sight of a wrinkly shar-pei; but many of us are now asking whether it is ethical to breed such genetic disasters simply to satisfy human vanity. The pros and cons of breeding cosmetic pets raised by the impending animal welfare bill have been well aired, and debate will open a can of worms. What has not been discussed is why we are so obsessed with breeding domestic monsters.

Ever since people started keeping pets such as dogs several thousand years ago, they have been changing them by selective breeding to suit their owners' needs. This process of genetic modification is what we call domestication. The term is not easily defined, but we all feel we know a domestic animal when we see one. A white mouse, a white rabbit, a white duck are all "domesticated" because they are different from their wild and cryptically coloured counterparts. Subconsciously, we know that a white rabbit would have much less chance of survival in the wild than a naturally coloured one. And this is the nub of domestication - it allows humans to produce animals in colours and shapes that wouldn't make it in the wild.

The passion for selective breeding, which began in earnest in the 17th century, blossomed in Victorian times. Everyone knew about it - the 19th century saw the development of large numbers of farm animal breeds, as well as dogs, cats, pigeons and canaries. Clubs were established to allow animal breeders to show the products of their efforts. The notion of improving animals via selective breeding was so widely known that Charles Darwin used it as an accessible analogy for his notion of natural selection, fully aware that, by comparing animal breeders' selection and rejection of breeding stock, everyone would grasp his principle. And they did. Before Darwin no one had paid much attention to the "science" of domestication, but it was part of Darwin's genius that he saw so clearly that domestication - once described as the greatest experiment ever conducted - provided the perfect analogy to sell his revolutionary ideas.

On The Origin of Species (1859) focused on the parallels between natural selection and domestication. But Darwin also realised that the process of domestication much more closely reflected his other great idea - sexual selection. Natural selection was caricatured as "survival of the fittest" but, as Darwin well knew, surviving is only part of the story - individuals also have to reproduce. The focus of natural selection was differential survival, but sexual selection was about differential reproductive success.

Eunuchs live a decade longer than intact men, but their genetic legacy is usually nil. Darwin's idea of sexual selection was based on two processes: competition between males to mate and female choice. The first of these was common sense: every farmer, pet owner and pub landlord had seen males fighting for females. Female choice was more controversial - not least because sexist Victorians wondered whether women were smart enough to make such tricky decisions.

Time has proved Darwin right, and both processes are now known to be important. Sexual selection is now recognised as an extremely powerful evolutionary force. The two processes often work hand in hand. The male peafowl's preposterous 2m-long train is a classic product of sexual selection. In the past, females chose to mate with long-tailed males, driving tail length longer with every generation. A longer tail would be sexier still. So why aren't peacock tails 3m long? The answer is that natural selection has put the brake on sexual selection. Peacocks with tails longer than 2m are easily captured by predators and would not survive as well as those with 2m tails.

In nature, natural and sexual selection work together to produce organisms best suited to their environments; the optimal compromise between the need to survive and the need to reproduce. In captivity, the constraints of natural selection can often be cast aside, allowing animal breeders to produce what many now call monsters and others think of as merely beautiful. The red jungle fowl (wild ancestor of the chicken) has a fancy tail as part of his seduction tackle. It is about 30cm long but, under the guiding hand of man, domestic cockerels of the Japanese Onagadori breed have been selectively bred with tails that trail 5m long.

Darwin kept many different pigeon breeds at his home in Down, Kent, so he could witness them at first hand. His favourite was the almond tumbler.

Selected for its colour, tumbling flight and stubby face, each and every almond tumbler chick was born by the avian equivalent of a Caesarean operation. Its beak was so short that it was incapable of hatching unaided and had to be helped out of the egg by its owner. In much the same way, today's bulldogs are all delivered by Caesarean because their heads are too big to allow natural birth. Whether almond tumblers suffer as a result of their reduced beaks is debatable.

Not only was domestication a convenient parallel to sexual selection for Darwin, as he himself wryly noted, sexual selection was the very reason men bred these bizarre creatures in the first place. "The action of unconscious selection, as far as pigeons are concerned, depends on a universal principle in human nature, namely on our rivalry, and desire to outdo our neighbours." Men appropriated the traits in animals, many of which had evolved through sexual selection, so that they could show off what wonderful breeders they were. The kennel clubs, canary clubs and pigeon societies were all stages on which men (it was and still is mainly men) could exhibit the products of their breeding skills. Fancy pets are an example of what Richard Dawkins calls an "extended phenotype" - an extension of our own seduction tackle. No one wants a loser.

Of course, the animal welfare bill is not restricted to pets. Farm animals are included, too. Just like pets, farm animals have also suffered at the hands of man. Darwin noted that "an attempt was once made in Yorkshire to breed cattle with enormous buttocks but the cows perished so often in bringing forth their calves that the attempt had to be given up".

Stockbreeders dressed up their efforts as a patriotic response to a need for more meat by a rapidly growing human population. But they were no different from pet fanciers, driven by their own prestige. The livestock breeders' self-indulgent endeavours resulted in beasts best remembered now by quaint portraits of the Durham ox. Those huge-bodied, tiny-brained cattle have now disappeared because they were practically useless. But they have been replaced by others no less monstrous. These include cattle with Pamela Anderson-sized udders, giant turkeys that are too obese and wobbly on their feet to mate naturally, diminutive Dexter cattle (which may suffer from the same problems as achondroplastic dwarfs), and prematurely ageing cloned sheep. Just because we eat them, do farm animals merit a different set of rules from pets? I don't think so.

We are all products of sexual selection to some extent. Expecting people to give up their pet-based quest for status is like asking them to give up sex. They won't: it is part of human nature. The best we can hope for is that the animal welfare bill will act like natural selection and put a sensible brake on the sexual selection process.

Tim Birkhead's book The Red Canary (Weidenfeld and Nicholson) describes the first genetically modified animal and is published on August 14; he will discuss his book at the Royal Institution on September 16. For tickets, call 020 7670 2985.