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Fabien asked:

I have recently heard that during a war the proportion of male births increases. Statistics show a more
than sensible augmentation of the male birth rate — as if we had some "social compensating" organ.
That would mean we are less individuals than we thought. If this is true which are the actual
explanations or theories about it?

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Aha! The supposed problem is this; if a population becomes embroiled in a war, many males will be
killed, and so the ratio of males to females will fall. Yet, mysteriously, go and examine the same
population a few years later and the ratio is back to normal. How can we possibly account for the
apparent change in the birth ratio of males to females?

There are two famous explanations. The first is that God has intervened to alter the normal course of
nature and correct the gender imbalance. By this, he not only restores His order, which foolish
mankind had upset, but demonstrates His very real existence and His willingness to intervene in
human affairs. I have heard exactly this explanation put forward by adherents of the Particular
Brethren.

The other explanation is that during the earlier phases of the human female's monthly fertile period,
the likelihood of conceiving males is equal to the likelihood of conceiving a female. But, later in the
cycle, males are more likely to be conceived. As a female can only become pregnant once in a
particular cycle, if a couple are having sex at fairly regular intervals it is likely that conception will
occur earlier in the cycle. If, however, men suddenly appear on the scene, after being absent for
some while, as happens when the menfolk return from war, then the chance of conception occurring
later in the cycle is increased, resulting in more male births. The work of the geneticist Koltzoff is
usually cited to support this one.

Convinced? I do hope not, because, with a little analytic application, we will see that the problem
does not, in fact exist. And we don't even need to look at any empirical statistics.

It is often difficult to examine clearly those problems which are full of fiddly little numbers. So let's
imagine an extreme case, and see what would happen there. Say that every man on earth, except
one, was killed. That would leave 1 man to about 3000 million women, a spectacularly extreme sex
ratio. Whether that one man was particularly sexually active or not, all the offspring of his unions
would appear, as they always do, roughly in the proportion of 1 male to 1 female baby. Go and have
a look at the population, a year later and we'd find that some babies had been born. Let us assume
that he had been busy and sired 100 children, 50 males and 50 females. The sex ratio over the entire
population would then have gone from 1:3000M to about 50:3000M, a fifty-fold increase in the
proportion of males. This looks impressive, until you realise that to get there the proportion of male to
female births was never anything other what we ordinarily expect.

As if that was not enough to damn the proposition, I'm afraid the "social compensation organ" couldn't
exist either. For what use would be extra infant boys to an excess of women short of mates? Those
boys would not become available as mates for 15 to 25 years, by which time the women would likely
be to old to make use of them.

So, now we've done the analysis, let's, like good philosophers, check our results against the facts. I
have the figures for Wales to hand, a small country which suffered great losses in the two world wars.
The male-to-female birth ratio is typically taken to be 1.07:1, though it varies quite a lot. True, the ratio
in Wales before the first world war was about 1.037:1, and after it rose slightly to 1.053:1, but even
that was still very much on the low side. But before and after the second world war it remained the
same at about 1.05:1. In fact the greatest male surplus was around war-free 1930 when it reached
1.147:1, and it has had upward 'blips' again in 1975 and 1996.

So, there's no need to invoke Godly intervention. I'm afraid the fertility-cycle-conception thing turns
out to be nonsense as well, though that doesn't seem to have stopped some less-than-honest clinics
trying to sell gender-selection services on the back of it, usually accompanied by an ingenious
twisting of Koltzoff's discoveries.

So, are we less individual than we thought? You and I are as individual as we think we are, but when
we're considering whole populations then individuality, of necessity, is lost. After all, we are only
humans.

Glyn Hughes