I had a call from a young woman in... from, well, she was in Boston then, and she was a graduate student doing her degree in economics and her name was Emily Oster. And she said that she'd read about the stuff, about the gender ratio and she'd gotten very interested in… in that and she had spent the next year or more collecting data to test in effect the predictions that you'd make from that model. Well, one of the predictions were if you looked just at broad population data, you'd expect there'd be a direct correlation between gender ratio, that is, males and females and the prevalence of hepatitis B. You know, the higher... if you have high prevalence, you have high gender ratios. If you have low prevalence of hepatitis B, you have low gender ratios. Well, she collected all that data from the medical literature and from demographic data from WHO and so forth and sure enough, there's a very high correlation, including China, you know, where they have one of the highest prevalences of HBV and one of the highest gender ratios, male to female. Okay, so that was pretty convincing. Then she went on to do some other things. She's very mathematically-oriented and she made some really fascinating mathematical models for all this.

So then the next thing was there'd been a nearly universal vaccination program in Alaska because Inuits, Eskimos, have a very high prevalence of hepatitis B, strangely. Other Native Americans, Indians, don't and… and Europeans of… and… and Alaskans of European origin don't have particularly high frequency, but the vaccination program was in place for about 15 years. It had been highly effective. Among the Native Americans back before vaccinations, they had 200–300 cases of hepatitis a year, after 10 years, zero. It was acute hepatitis and the prevalence went down. So she looked at the vaccination data. So the model is, okay, you would expect that you would get a decrease in gender ratio in the Inuits and the Eskimos because they were under… they were influenced by the hepatitis infection but not the Indians or in people of European origin. That's exactly what she found and she did a similar but rather more sophisticated study in Taiwan and the results were complex but generally speaking...Okay so that, first of all that… that was a direct test of the model, right? And now that meant it's ideologic and it causes the germ because if you remove it, the gender ratio changes... That's not a disease, you know. Having a boy or a girl isn't a disease. That… effect, a profound effect on human populations. Now it's hard to tell what, you know, there're a lot of things that determine gender ratio. At an individual level, it might be hard for anybody to know, but at a demographic level, at a population level, in a place like China which is moving towards a universal vaccination and where they have one child, there's a one child rule, which is pretty strictly adhered to, except, with some exceptions by the way, foreign families, minorities, you know, can have more than one child. Now, there may be some effect, you know, may not influence single childs [sic] as much as it does whole communities. We never actually did a study in China but nevertheless this raises that… this raises that question about the demographic effect. Now as far as I know, nobody's ever looked in humans anyhow on viral effects on gender ratios. There… there are studies in other… in other species and I… and there… I'm sure there are other… there other factors that have maintained this in the population.

[Q] That's fascinating. And no idea what the mechanism is?

Well, we have a bunch of ideas but we haven't… we haven't tested, you know, I'm not… I don't have a lab any more and… but I think particularly since… since Emily's research, I think there'll be more… be more work on it and I continue to speak on it and people… but you see it's… it's not the sort of thing you would do, you know, if you’re trying to, you know, if they tell you, in your department… well, listen we got to develop drugs. Are you going to work on gender ratio? Well, the answer is yes, you should because among other things, if you can figure out what that... that is, you're not going to, I mean I hope it's never used for determining, you know, for influencing gender outcome in humans, but think of what it would do in cattle raising. You know, you… you have a herd where you… you want… you have really great cows and… and you… you want to increase them or you want to raise steers, you know, your beef production, you know, your... you know, dairy production and you want… you want to be able to affect, you know, gender ratio.