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 over-estimated 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 enemies of life. The great struggle, we are told, is to adapt to these conditions. The things that kill animals or prevent them from reproducing are only rarely physical factors. Far more often they are other creatures - parasites, predators and competitors.
-- Matt Ridley