The Bishop of Edinburgh is not the first nor probably the last cleric to look to nature for an explanation of human sexual desire. A century or more ago, a Reverend FO Morris, a keen amateur naturalist, was so impressed by the tranquil monogamy of the common hedge sparrow, or dunnock, that he implored his congregation to follow suit. The dunnock ''exhibits a pattern which many of a higher grade might imitate, with advantage to themselves and benefit to others through an improved example,'' he wrote with the pomposity of a true Victorian clergyman.
Unfortunately, scientists have since exposed the dunnock for what it is, an animal that engages in promiscuous liaisons with abandon. Often one female dunnock can be found being serviced by two males. If Morris's congregation had followed his advice ''there would have been chaos in the parish,'' according to Nick Davies, the Cambridge zoologist who studies the dunnock's bizarre sex life.
The bird has shown that promiscuity, even for supposedly monogamous species, is more common in nature than was once supposed. What is surprising is that this is true for females as well as males, the traditional sowers of wild oats. Females, it seems, are not averse to a bit on the side if it gives her offspring a better chance in life. Sneaky sex with the well- endowed male next door is not a bad evolutionary strategy, providing your own partner does not find out and abandon the nest as a result.
This is all very well for songbirds, but what about humans? To understand our own complex sexuality, biologists frequently look to our closest living relatives, the great apes, paying particular attention to the size of their testicles. It has long puzzled biologists as to why men should have such relatively large testicles, similar in comparative size to the highly promiscuous male chimpanzee, which copulates hundreds of times with dozens of females. On the other hand, a male gorilla, which faithfully waits for up to a year to mate with his female, is not so well endowed.
To suggest that men are rampant chimps at heart, purely on the basis of their testicle size, is probably one logical jump too many. There is, for instance, another species of chimp, the bonobo or pygmy chimp, where promiscuity of both sexes is taken to the extremes of free love. In bonobo society, promiscuity, even between members of the same gender, acts like a glue that keeps the society together.
What makes humans so different from other apes is the complexity of our behaviour and social organisation, which is not under the direct control of our genes. In human societies, polygamy, life-time or serial monogamy and even polyandry all exist. Which system predominates often depends on the disparities in the wealth of the society in question. Very rich men living alongside very poor men often take many wives, whereas poverty- stricken societies, such as the farmers of Tibet, often result in a women taking two husbands to help rear a family.
The Bishop of Edinburgh is right to say that we are all sexual animals, with a genetic predisposition to promiscuity. He is also right to say that life is never a simple case of genetic determinism. It would be foolish to believe that we are slaves to our genes. Far from it, the fact that we have liberated ourselves from many of the rules laid down by nature is the very essence of humanity, which is a sentiment no doubt shared by the bishop.Reuse content