Like a Virgin, Prasad, Aarathi [free children's ebooks pdf .TXT] 📗

Still, against the odds, the human Y chromosome does not seem to be taking its destruction lying down. Even though it is at a distinct disadvantage by not having a perfect partner match in the cell, it has developed ways to ensure its survival. To get rid of accumulating damage and mutations, the Y chromosome has been swapping its bad bits with intact bits of itself. While this has fixed the problem to a certain degree, it has introduced other places where mistakes can happen. Once the DNA on a Y chromosome is broken up so that it can be swapped, the pieces sometimes end up being put back together incorrectly. This self-protection stratagem triggers a whole range of sexual disorders in otherwise healthy men, including less sperm production, sterility, and sex reversal, as in de la Chapelle syndrome.

Should the Y chromosome crumble into scant genetic bits and bobs, and then disappear altogether, it would not necessarily mean the end of a species. There is hope. Some animals, such as the mole vole (Ellobius lutescens) and the Japanese Ryukyu spiny rat (Tokudaia osimensis), have two sexes but no visible sex chromosomes. The voles, a rodent that burrows underground throughout a wide swathe around the Caucasus mountains, are extremely interesting for one reason: it is impossible to distinguish a female from a male by looking at their chromosomes; both carry only a single X. What is more, scientists have been unable to pick up any bits of SRY gene on any chromosome in the mole vole species. Since SRY normally acts as the primary switch that initiates the development of a testis out of the undecided mass of cells in an embryo, you would expect to see it in an animal that looks male. It’s not there.

Unlike with the XX male cocker spaniels, pigs, and goats, sex reversal is the norm of the male mole vole, not the rare exception. How does the species survive? Male mole voles do have small testes and problems in generating healthy sperm, but no hermaphrodites have ever been recorded in these animals. It appears, however, that testosterone is not very efficient in the males; the prostate gland, in fact, seems to be insensitive to the effects of the hormone. Still, in captivity at least, mole voles seem to have little problem breeding. Fifty percent of early embryos perish, but certain mole vole couples have been seen to give birth to a litter of up to six pups – and they did that every four to six weeks, eleven times.

The mole vole story may give us a hint about the future of humanity. Even if the human Y were to disappear, it wouldn’t necessarily follow that men will vanish, too, though male fertility would likely become substandard, adding another spanner in the works of making babies whenever you like. Infertility might one day affect all young, otherwise healthy men. And if the trend for women having babies later and later in life continues, the health and quantity of their eggs will also be an issue. The limits of time is undeniably something we need to address, perhaps by correcting genetic mistakes in embryos, a technique that is already being discussed but raises the spectre of eugenics in many circles.

Better answers will probably come from social policy rather than biology: discussing with young people the biologically optimal time to have babies, at the same time as they are taught how to prevent pregnancies; more support for people who have children at a young age; more extensive childcare, benefits, and incentives to allow for family and work to exist side by side. After all, right now, IVF treatments are invasive, difficult, and very expensive. For many people, however, ‘losing’ their youth to parenthood is neither an ideal nor a practical life choice. It’s very hard to get away from the uncomfortable fact that it is educated women who tend to have babies later in life. It has even been suggested that an effective way to control overpopulation would be to increase women’s rates of literacy. In any case, many women who have access to education and work opportunities are not going to turn them down in order to have babies at a young age and at the risk of slipping behind their male colleagues on the career ladder. The goal

should be to give everyone these opportunities, not to snatch them away from those who have won them.

In a world where men and women now very often face the same social prospects, our reproductive biology has not kept pace. Normally, men produce sperm, women under thirty-five have eggs, women bear children, and men cannot. There is a clear division between the sexes. That, however, is set to change.

8

REAL MEN BEAR CHILDREN

Women’s liberation is just a lot of foolishness. It’s the men who are discriminated against. They can’t bear children. And noone’s likely to do anything about that.

Golda Meir, quoted in Newsweek, October 1972

In 2008, scientists at the New South Wales Department of Primary Industries, in Australia, developed the first artificial womb. It was a plastic container specially designed to hold fluids, bacteria, and the other stuff that is needed to mimic the conditions found inside the mother as an embryo develops. It was a phenomenal breakthrough. Especially if you were a grey nurse shark, the species for which the womb had been developed.

For aquatic ecosystems scientist Nick Otway, the artificial womb was a tool for addressing a terrible problem. The grey nurse shark, also known as the sand tiger shark, has roamed the world’s oceans for more than seventy million years, but in the past century, the species has been decimated by increased fishing. Though it is not the target of the fishing