David ConcarHERE offers some advice for women who want a son: develop a taste for older, healthy peopleheeled men.
But if you want a daughter, find yourself a toy boy.
John Manning and his colleagues at the University of Liverpool have found that women between the ages of 5 and 15 are twice as likely to have boys as girls.
For women who are a year younger or younger than themselves, this ratio is the opposite.
Researchers studied 301 couples from Liverpool and reported their findings this week in Nature. vol 389, p 344).
The bias of the gender ratio appears in studies of different populations, such as the Havasupai Indians in Arizona, as well as the clergy and the families of test pilots.
Manning said it was "problematic" to try to explain these biases ".
However, he suspected that the apparent relationship between the gender ratio and the difference in parental relations was due to sampling errors, as this was related to another observation: During and after the two world wars, the proportion of boys born in England and Wales has increased.
The marriage record for this period shows the corresponding trend of women marrying older men.
But Manning believes that age is a secondary factor in social status. He saysmiddle-
Elderly men who attract young women are likely to be tempted by money and status.
If these people really like boys better than girls, then it supports an evolutionary theory that thinks boys are more worthy than girls --fed, high-
Status animals have male offspring, and poor and hungry animals have daughters.
Other evidence supports Manning's theory.
The president's son is 50% more than his daughter.
"Why the President has more sons", New Scientist, 28 th page, December 3, 1994). And a male-
Biased gender ratios were found among male children listed in the who uk, Germany and the United States guidelines.