The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [53]
The answer to the question ‘Would you not avoid paying the cost of maleness by being a hermaphrodite?’ is simple: yes, but there is no way to get there from here. We are stuck with two genders.
The Case of the Immaculate Turkeys
By separating their genders, animals ended the first mutiny of the organelles. But it was a temporary victory. The organelle genes renewed their mutiny, this time with the aim of driving all males into extinction and leaving the species all-female. This might seem to be a suicidal ambition, because a maleless, sexual species would become extinct in one generation, taking all its genes with it, but there are two reasons why this does not faze the organelles. First, they can, and do, convert the species into a parthenogenetic species, able to give virgin birth without sperm – in effect, they try to abolish sex – and second, they behave like cod fishermen or whale hunters, or the grazers of commons. They seek short-term competitive advantage, even when it leads to long-term suicide. A rational whale hunter does not spare the last pair of whales so that they can breed; he kills them before his rival does, and banks the proceeds. Likewise, an organelle does not spare the last male lest the species go extinct, for it faces extinction anyway if it is in a male.
Consider a ladybird’s brood. If the male eggs die, the female eggs in the brood eat them and get a free meal as a result. Not surprisingly, there are male-killing genes at work in ladybirds, flies, butterflies, wasps, bugs – about thirty species of insects so far studied – if, and only if, the young in a brood are in competition, one with another. These male-killing genes are not in organelles, however, but in bacteria that live inside the insects’ cells. Those bacteria, like the organelles, are excluded from sperm but not from eggs.31
In animals such genes are called sex-ratio distorters. In at least twelve species of small parasitic wasps called Trichogramma, a bacterial infection makes the female produce only female young even from unfertilized eggs. Since all wasps have a peculiar system of sex determination in which unfertilized eggs become male, this does not condemn the race to extinction and it helps the bacterium to get into the next generation, via the cytoplasm of the egg. The whole species becomes parthenogenetic for as many generations as the bacterium is there. Treat the wasps with an antibiotic and, lo and behold, two genders reappear among the offspring. Penicillin cures virgin birth.32
In the 1950s scientists at an agricultural research centre in Beltsville, Maryland, noticed that some turkey eggs began to develop without being fertilized. Despite heroic efforts by the scientists, these virgin-born turkeys rarely progressed beyond the stage of simple embryos. But the scientists did notice that vaccinating the fowl against fowl pox with live virus increased the proportion of eggs likely to begin developing without sperm from one or two per cent, to between three and sixteen per cent. By selective breeding and the use of three live viruses, they were able to produce a strain of Pozo Gray turkeys nearly half of whose eggs would begin to develop without sperm.33
If turkeys, why not people? Laurence Hurst has pursued an obscure hint of a gender-altering parasite among human beings. In a small French scientific journal, there appeared in 1946 the astonishing story of a woman who came to the attention of a doctor in Nancy. She was at the time having her second child, the first, a daughter, having