He explains why almost all sexually reproducing animals have two genders, with standardised roles in reproduction. The battle to determine which would survive could destroy the fertilised egg. Also, if only one of the partners provides a full cell, the offspring can inherit viruses and bacteria from only that partner, rather than both. All of the organelles in your body came from your mother, none came from your father. This is bad news for the genes, whose life s work, remember, is to pass into the next generation.
Every man is a dead end for organelle genes.
The most attractive solution for an organelle gene in a hermaphrodite is to divert all of the owner s resources into female reproduction and away from male. This is not pure fantasy. Hermaphrodites are in a state of constant battle against rebellious organelle genes trying to destroy their male parts. Male-killer genes have been found in more than a hundred and forty species of plant. It is only when he ventures onto the subject of human sexuality that Ridley s argument becomes visibly weak.