GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2009-10 > 1256803865
From: "Alister John Marsh" <>
Subject: Re: [DNA] Significance of "First Mutation" in aTree. Sexof Childrendetermined by fathers DNA.
Date: Thu, 29 Oct 2009 21:11:05 +1300
Note what the author says about the example trees:
The trees, below, illustrate how the gene works. It is a simplified
example, in which men either have only sons, only daughters, or equal
numbers of each, though in reality it is less clear cut.
I wondered if by the "in reality it is less clear cut" comment, he was
really referring to the FM and MF cases. He showed them with exactly half
boys and girls. The reality is that if the FM and MF fathers statistically
would "average" 50/50 boys/girls, in more individual cases than not they
would not have "exactly" 50/50 which was shown in the example. They might
have 2 girls/ 4 boys, or 4 boys/2 girls, or 1 boy/ 5 girls, 5 boys/ 1 girl
etc, or even 6 boys or 6 girls
In my view he was inferring that MM would only produce boys, and FF would
only produce girls. Those cases would I suggest always absolutely follow
the rule, but in the FM or MF case, you can't in just 1 or 2 examples
represent all of the possibilities for a statistical probability of 50/50
for each birth.
I agree with you the more sons after wars scenario as put forward was a bit
of speculative leap. It is likely more complicated than that.
More sons after a war might even be caused by a psychological effect.
Perhaps after a war fathers producing sons, like hypothetically MM fathers,
might for some reason be psychologically motivated to keep producing sons,
while a FF father producing daughters might stop at half a dozen. The
effect may be psychological changes in the father from his war experiences,
or an effect coming from the society as a whole.
After a war, if the male population has been significantly reduced in
proportion to females, there might subliminally be social approval of MM
fathers producing many sons, which may psychologically motivate those
fathers to respond to the societal approval by continuing at stud longer.
I know someone who lost 3 sons, and as a consequence the surviving son was
perhaps regarded with more importance than his sisters. If there is seen to
be a societal need for an increase in male numbers, or more "value" placed
on males because of a recent loss of males, the societal approval of more
sons may affect the self esteem of the MM fathers producing sons, to
encourage them to keep at stud longer.
This might be tested by checking trees to see if fathers who had 6 sons were
more inclined to keep breeding longer than fathers who had 6 daughters. If
that were the case, it might be a result of the MM and FF biases which
enables increased male births in circumstances of need.
If for some reason society had a shortage of girls, FF fathers producing
daughters might respond to subliminal societal approval and keep at stud
There you go... I have a weird hypothesis of my own. I could no doubt think
of a dozen more equally improbable reasons also.