Olivia Judson is a research fellow Imperial College London.
In 1853, the Reverend Francis Morris urged everyone to imitate the virtuous, humble behaviour of the dunnock, a small brown bird that lives in hedges. He was hardly the first to advocate that people take moral lessons from nature. More than a century before, Isaac Watts wrote a series of ghastly, saccharine poems to admonish children - for example: "Birds in their little nest agree / And 'tis a shameful sight / When children of one family / Fall out, and chide, and fight"; and "How doth the little busy bee / Improve each shining hour, / And gather honey all the day / From every opening flower!".
In the 20th century, leading thinkers justified social policies - such as forced sterilisation of the "mentally unfit" - on "natural grounds". Even today, it is common to hear that some behaviour or other is "unnatural" and therefore wrong, or "natural" and therefore okay. But is nature really a great source for our moral code? The reverend might have been less enthusiastic if he'd known what dunnocks really got up to. Had his parishioners engaged in real dunnock behaviour, they would have been rewarded with more exciting sex lives than most of us have now. If Mr Watts had known that some birds routinely murder their brothers and sisters - among some eagles, for example, the first chick to hatch kills the second - he, too, might have been less quick to appeal to nature as a role model.
Even honeybees are not so exemplary. Sure, the females work hard, but they also engage in cannibalism, eating alive larvae that have genetic defects. And what about the drones, who do not help collect nectar but laze about waiting for their chance to mate? Then there is the sex act itself. The queen mates on the wing with any male who can catch her. Any male who does, explodes - literally - and falls to the ground leaving his amputated genitalia in situ.
In human terms, the natural world is often a dark place. In her book, The Chimpanzees of Gombe , Jane Goodall writes that "infants, juveniles, and adolescents typically copulate with females". Bottlenose dolphins don't restrict their sexual advances to their own species. Males have been recorded attempting to copulate with sharks, turtles, seals, eels and, occasionally, humans. In the mite Acarophenax mahunkai , brothers and sisters copulate with each other inside their mother, who then bursts. Male lions kill all the cubs they can find when they take over a pride. The male Japanese cardinal fish broods his young in his mouth. But if he sees a female more attractive than the one he mated with, he swallows his offspring and hurries over to the new female to press his suit. For the endangered Hawaiian monk seal, the biggest cause of death is other Hawaiian monk seals. Mobs of amorous males frequently batter females to death. As Darwin observed: "What a book a devil's chaplain might write on the clumsy, wasteful, blundering, low, and horribly cruel works of nature!"
Why does all this go on? Nature is amoral; it has nothing to do with right and wrong. A behaviour that helps an individual to have more and healthier children can spread through a population irrespective of whether it is harmful to others or benign. Among lions, for example, killing cubs brings the females back into heat. It is a common misconception that evolution is about propagating a species. It is about individuals propagating their genes. Species can become extinct as a result of the collective effects of individual behaviours.
Like all other organisms, humans have evolved. Thus, the study of animal behaviour and genetics can tell us a lot about why we are the way we are - and why some urges are so hard to control. But as a guide to how we should try to live? Forget it.
Olivia Judson's book, Dr Tatiana's Sex Advice to All Creation , is published by Chatto and Windus.