The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [32]
Sex, according to the Red Queen theory, has nothing to do with adapting to the inanimate world – becoming bigger, or better camouflaged, or more tolerant of cold, or better at flying – but is all about combating the enemy that fights back.
Biologists have persistently overestimated the importance of physical causes of premature death rather than biological ones. In virtually any account of evolution, drought, frost, wind, or starvation loom large as the enemies of life. The great struggle, we are told, is to adapt to these conditions. Marvels of physical adaptation – the camel’s hump, the polar bear’s fur, the rotifer’s boil-resistant tun – are held to be among evolution’s greatest achievements. The first ecological theories of sex were all directed at explaining this adaptability to the physical environment. But with the tangled bank, a different theme has begun to be heard, and in the Red Queen’s march it is the dominant tune. The things that kill animals or prevent them reproducing are only rarely physical factors. Far more often they are other creatures – parasites, predators and competitors. A water flea that is starving in a crowded pond is the victim not of food shortage but of competition. Predators and parasites probably cause most of the world’s deaths, directly or indirectly. When a tree falls in the forest, it has usually been weakened by a fungus. When a herring meets its end it is usually in the mouth of a bigger fish or a net. What killed your ancestors two centuries or more ago? Smallpox, tuberculosis, influenza, pneumonia, plague, scarlet fever, diarrhoea. Starvation or accidents may have weakened people, but infection killed them. A few of the wealthier ones died of old age, or cancer, or heart attacks, but not many.22
The ‘great war’ of 1914–18 killed twenty-five million people in four years. The influenza epidemic that followed it killed twenty-five million in four months.23 It was merely the latest in a series of devastating plagues to hit the human species after the dawn of civilization. Europe was laid waste by measles after AD 165, by smallpox after AD 251, by bubonic plague after 1348, by syphilis after 1492, by tuberculosis after 1800.24 And those are just the epidemics. Endemic diseases also carried away further vast numbers of people. Just as every plant is perpetually under attack from insects, so every animal is a seething mass of hungry bacteria waiting for an opening. There may be more bacterial than human cells in the object you proudly call ‘your’ body. There may be more bacteria in and on you as you read this than there are human beings in the whole world.
Again and again in recent years, evolutionary biologists have found themselves returning to the theme of parasites. As Richard Dawkins put it in a recent paper:
Eavesdrop [over] morning coffee at any major centre of evolutionary theory today, and you will find ‘parasite’ to be one of the commonest words in the language. Parasites are touted as the prime movers in the evolution of sex, promising a final solution to that problem of problems.25
Parasites have a deadlier effect than predators for two reasons. One is that there are more of them. Human beings have no predators except great white sharks and each other, but they have lots of parasites. Even rabbits, which are eaten by stoats, weasels, foxes, buzzards, dogs and people, are host to far more fleas, lice, ticks, mosquitoes, tapeworms, and uncounted varieties of protozoa, bacteria, fungi and viruses. The myxomatosis virus has killed far more rabbits than foxes have. The second reason, which is the cause of the first, is that parasites are usually smaller than their hosts while predators are usually larger. This means that the parasites live shorter lives and