Jan 25, 2006 - 2:14:00 PM, Reviewed by: Priya Saxena
"After the last World War there was a dramatic increase in the number of boys born and this theory cannot explain how that was achieved. It's a very complex area of biology"
By IANS, [RxPG] Stress during a disaster particularly after natural calamities like earthquakes and severe famine can cause the death of weaker male foetus but those that survive may live longer than the average, says a study.
It is known that fewer boys tend to be born during times of hardship, such as a natural disaster. Male foetuses and embryos are weaker than those of females and are less likely to survive.
Researchers at the University of California examined data on Swedish births from 1751 to 1912 and found why the proportion of newborn boys often dips sharply during times of stress, reported the online edition of BBC News.
Mothers' bodies under stress have less tolerance for unhealthy embryos and foetuses and thus spontaneously abort offspring that would have been otherwise carried to birth, they said.
Writing in Proceedings of the National Academy of Sciences of the US, researchers concluded aborting boys may be a way to maximise the odds of survival of the bloodline.
According to them, only weak foetuses were selectively targeted by the mother's body, giving more robust males every opportunity to thrive.
They argued that actively culling weak male foetuses might increase the overall chance that a woman's genetic line will survive down the generations, as weak individuals were more likely to produce fewer offspring.
However Allan Pacey, an expert in andrology at the University of Sheffield says: "There must also be other mechanisms at play to manipulate the sex ratio in other situations.
"After the last World War there was a dramatic increase in the number of boys born and this theory cannot explain how that was achieved. It's a very complex area of biology," he said.
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