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[escepticos] Parental age gap determines sex of first child



Hola, hola.

Esto está relacionado con el tema que surgió por aquí hace tiempo del
sexo relacionado con el momento de la concepción (dentro del ciclo
menstrual, no con relación a Júpiter) y aquello del nacimiento de
varones tras las guerras.


Parental age gap determines sex of first child

LONDON (Reuter) - Women who marry much older men are more
likely to have a son as their first child, British researchers said
Wednesday. John Manning and colleagues at the School of Biological
Sciences at the University of Liverpool in northern England studied
301 families and recorded the differences in the age of mothers and
fathers and the sex of their children.
``We show that the age difference between parents predicts the sex of
the first child,'' he said in a letter to the scientific journal
Nature. Women whose husbands were more than five years older tended
to have boys first, but if their partner was younger or the same age
their first child was usually a girl.
``We found that this was the case but only for first born children.
We don't know why, but that is the case in our data,'' he said in an
interview. Manning's findings support other studies showing more boys
are normally born during and shortly after periods of war or
hardship.
``We predicted from our data that might arise because marriages
during those kinds of periods of stress may involve a greater than
usual age difference between partners,'' he said.
In most societies men are an average two years older than their wives
or partners, but studies in England and Wales have shown that the age
gap increased during both World Wars, and there was a corresponding
rise in the number of male births.
Manning said that rank in many animals is related to the
sex of their offspring and the same is true of humans.
``Human elites tend to have more sons than daughters. If
you look at American presidents on the whole the number of sons they
had exceeded the number of daughters. It is also the case for
European royalty and aristocracy and business leaders.''


Saludos, Carlos Ungil