Sir

In this bicentennial year of Charles Darwin's birth, it is gratifying to see Nature devoting a wealth of comment to the great man and to evolution. But like much other scholarly perspective, your emphasis is on natural selection, the first of Darwin's great ideas.

Yet his second great thesis, on sexual selection, is in some ways his greatest work, because it is far less obvious than natural selection. After all, Alfred Russel Wallace also discovered natural selection, but no one else envisaged anything like sexual selection, which, even after Darwin's exposé, remained something of an anathema. Sexual selection is responsible for some of the most spectacular behaviours and characters in nature (picture the peacock's tail), but it was largely ignored during the modern synthesis and only really became mainstream in the 1970s.

Since then, we have come to realize the importance of sexual selection for much of biology, from driving rapid molecular evolution to speciation, the subject of Darwin's best-known work, On the Origin of Species. In this celebratory year, we need also to acknowledge the importance of this historically maligned mechanism of evolution.