NOT all the victims of 9/11 died in the towers or the crashed planes. A higher than average number of male fetuses died in the US in the following months, a study of birth rates suggests.
At times of great stress, such as the social and economic turmoil that followed the reunification of Germany in 1990, sex ratios become slightly skewed towards females (New 杏吧原创, 30 August 2003, p 20). But until now it has not been clear whether this is because fewer males are conceived, or whether fewer males already in the womb survive.
Ralph Catalano鈥檚 team at the University of California at Berkeley examined records of birth and miscarriages in the state, where all fetal deaths after the 20th week of pregnancy must be recorded. The researchers found that about 2 per cent fewer healthy males and 29 per cent fewer low-birthweight males were born in December 2001 than expected. Figures for October and November showed that a quarter more male fetuses died than would normally be expected (Human Reproduction, vol 20, p 1221).
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Catalano thinks high levels of stress hormones in pregnant women could be to blame. The phenomenon might be an evolutionary mechanism designed to cull the weakest males when times are hard. 鈥淚t鈥檚 not in the interest of the herd to have small, weak males around,鈥� he says.
