Mendel’s Demon by Mark Ridley, Weidenfeld & Nicolson, £20,
ISBN 0297646346
THIS is a book about sex. Why is it an essential requirement for the
existence of complex creatures like us? Cloning is a much more straightforward
mode of reproduction. Bacteria and many other creatures are happy to reproduce
this way. So why bother with sex?
When an organism copies its DNA, mistakes—mutations—inevitably
occur. Natural selection can remove these from the gene pool, but only if the
mutation rate is low enough.
This strategy works for bacteria. They only have to copy about 5000 genes.
Humans have tens of…
