A coworker just e-mailed me a little blurb about how more males are born during war time, nature replenishing the herd, etc. etc. Going strictly on anecdotal evidence, this bears out among us here in the office (two expecting boys), my son’s daycare (four of us expecting boys) and my family (three more boys!), but I’m a bit skeptical that it is actually true overall. Are there any studies that have actually borne out this claim?
That wouldn’t make sense from an evolutionary standpoint anyway. Increasing the percentage of males does nothing to accelerate population growth or replenish a diminished population, since it’s (obviously) the females that bear the young. Certainly large-scale warfare hasn’t been going on long enough for there to have been any significant evolutionary repsonse to it. I haven’t found a study on this one way or the other, but for now, I’m going to have to call BS on this one.
Certainly males die disproportionately during war. But the fact that the extra males ostensibly conceived during the time of war wouldn’t be sexually viable for quite some time. Then, fifteen to eighteen years hence, there would be a glut of men.
I can see why this would be a compelling story (and incidentally, my own anecdotal sample bears it out 
) but sounds glurgey.
That’s what I was thinking too guys. Glad I’m not just a hopeless cynic. 
Well, I’d be really interested in how, exactly, the Y sperm know there’s a war on and put forth that extra effort to “support our troops”, so to speak.
Anecdotal evidence is bad because it’s a really small sample. Hell, everybody I know who’s pregnant or just had a baby has girls.
Here I go with the book recommendations again. Matt Ripley’s The Red Queen: Sex and the Evolution of Human Nature is, I believe, the source of a related factlet that I recall. The basic theory is that while the X and Y sperm don’t know that a war is on, war obviously causes a lot of stress. Stress interferes with the mother-to-be’s hormone level, which can affect the sexual orientation and development of the fetus. So IIRC, wartime was not necessarily related to more males or females being conceived, but to the development of more homosexuals developing.
Maybe the fellow that just transported him here was wearing a battle helmet?
Two sperms swimming along:
Sperm 1 - Are we nearly there yet?
Sperm 2 - You must be joking, we’ve only just passed the epiglotis.
Yes more boys are born during war time, but more boys are also born during peace time. I think it’s 105 male births to every 100 female births in the US, which is pretty standard if things are done naturally. In China though, the the figures of reported live births is somewhere close to 115 to 100, at least as I remember.
This is probably attributable to selective abortion, male children being considered in that society more desirable than females. IIRC India has a similar tale to tell.
Apropos the original question, what is supposed to be the mechanism for an increase in males? Do women hear of the war and somehow change their metabolism? It seems hard to imagine how this would work.
And there is the important point that evolution works on the gene level, not the level of a society. Though I suppose you could postulate a gene that “sees” an “opening” for males that could be exploited.
Nearly. Ridley states the “returning-soldier” effect to be a fact - more males are born during and shortly after wars. There is a good deal of evidence that the hormone levels in the mother (gonadotrophin) and father (testosterone) affect the sex of the offspring. It has been postulated that war changes the role of the typical women, which affects her hormone levels, resulting in more males.
Interesting, because i once read an article that explained how male homosexuality was a group survival adaptation. The idea was that homosexuals are basically a natural version of eunuchs - they had the strength and other assets of men but the warriors could leave them with their women without fear of losing them to men at home.
If anything, I would expect a greater proportion of girls to be born in war-time, due to poorer diets and increased stress. See Is there anything we can do so we have a boy?.
I have attempted to find statistics for the Sex Ratio at Birth for the United Kingdom in the 20th Century - it would seem to me that the above implies more girls during the Second World War and I am confident that the data exists … somewhere! I’m just not familiar enough with demographic resources on the Web to find it other than by dumb luck, however, and I’m not having much tonight.
The appropriate paragraphs from Ridley’s Red Queen are reproduced here, about two-thirds of the way down the page.
In the book, Ridley also mentions some animals producing more females in times of stress. The theory is that as the females are smaller, they are easier to “grow” and therefore less likely to be spontaneously aborted. I don’t know that this would apply to humans, though, where there is little difference in size between males and females at birth.
Could be a thread killer as has happened before. I was once told by a father of all girls that " Anyone can make a boy, but it takes a real man to blow the nuts off 'em"