Masculinity affected by female genes says scientist

An extra set of female genes appears to make males more masculine (New Scientist, 10 March 2012). This suggests that sex chromosomes, rather than hormones, have a role in directing behaviour, says Emilie Rissman of the University of Virginia in America.

Rissman suggests that it commences soon after birth. Male foetuses are exposed to testosterone from four weeks of age, while females are not.

To determine whether sex chromosomes affected sex-specific behaviours beyond dictating the presence of hormones, Rissman took advantage of a mutation in mice that causes the sex-determining region of the male Y chromosome to jump to a non-sex chromosome. The mice are male, but have two X chromosomes (typically female chromosomes). [Genetically, if an animal or human has XX chromosomes, it is female; if it has XY chromosomes, it is male.]

While the XX male mice had the same level of testosterone as normal XY male mice, they displayed more masculine sexual behaviours, such as mounting females more often and ejaculating more frequently. To confirm that the differences were a result of a hidden factor on the X chromosome and not the lack of the Y chromosome, Rissman compared XY male mice with XXY male mice which carried an extra X chromosome. The result was that the XXY mice also showed more male sexual behaviours.

The extent to which these findings are generalizable and transferable to humans remains to be determined. However, the idea might provide an explanation for evidence that XXY men have more sex than men with the regular XY chromosomes. If Rissman can identify a part of the X chromosome linked to sexual activity, its protein products could be a target for libido-boosting therapies.

Interestingly, my novel, Bardot’s Comet (2011), set in The Sixties about a genius-level female mathematician raised by a migrant single father, discusses feminism, masculinity, androgyny, and sexual behaviours through a discourse on chromosomes.

A modified excerpt is as follows:

     “I heard a scientist talking about genes. I interviewed him actually. He talked about how foetuses with XY sex chromosomes develop into boys and those with XX sex chromosomes develop into girls. He was saying that, if a foetus is not sensitive to androgens, such as testosterone, then XY foetuses develop into girls and not boys. He was speculating it happened to you: that you had XY chromosomes, male chromosomes, but that you developed into a woman.” The tape-recorder clicked off and Philip flipped the tape and re-inserted it.

     “That’s interesting. Tell me more,” she smiled.

     “Well, he said that if that happens, a person looks like a woman; she has breasts and she doesn’t have excessive hair or anything like that, but she may look a bit manly.”

     “Really?”

     “Well you’ve got to admit that you have strong masculine shoulders. You’ve got muscles and you’re fit. And you don’t have a big butt like most women have.”

     Prudence laughed. “Big butt! So I don’t have a big butt! That’s good. Anything else?”

     “He said, the scientist said, that outwardly you’re female, but you might have smaller breasts than most women, have a high incidence of osteoporosis and other bone diseases, you might not menstruate, and therefore you might not be able to conceive children. That’s why you don’t have children. That’s what he said. He said, basically, that you are really a man.”

     “But don’t some people think that I’m a radical, lesbian feminist too?”

     “Well yes, but the scientist doesn’t think that. His theory is that you’ve got male chromosomes; you look like a woman but you’re really a man. You’ve got the mind of a man. Your brain is like a man’s brain. That’s why you’re good at mathematics and science. That’s why the scientist thinks you’re not really a woman. Do you see what I mean? He says if you are a man that likes women, you are therefore not a lesbian. But if you are a man that likes men, then you are homosexual. He even said that it would be interesting doing psychological tests on you to assess your personality. He thinks it might prove that you have a man’s brain. That’s what he said.”

     Prudence was laughing. “Sorry Philip, I can’t stop laughing at how ridiculous this is. I’m so glad you told me. And it’s all so confusing. So, am I a lesbian, a gay man in a woman’s body, androgynous, or am I just an ordinary person? You tell me. This scientist believes that I’m a man. Who is this scientist? What’s his name? I want to see his work and his analysis. Who is this scientist?” She was leaning forward, expecting an answer.

     “But Professor, if his theory is true for women, could it be true for men? Like, could some men have XX sex chromosomes and still look male, but have the qualities of a woman? It couldn’t be true, could it?”

     “I don’t know. I’m not a doctor. What’s the scientist’s name and I’ll ask him?”

     “I shouldn’t have mentioned it. I can’t tell you his name. He said that his work is experimental and that people wouldn’t believe him yet. I’m not even allowed to write about it. He said that if anything is printed and his name is mentioned, he’d sue me, or kill me: one or the other. He said that he’d make his work known sometime in the future, in the next couple of years, maybe.”

MARTINA NICOLLS is an international aid and development consultant, and the author of:- The Shortness of Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet (2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).