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Monkey 'murderers' may be falsely accused

作者:随针贷    发布时间:2019-02-28 02:01:06    

By Rosie Mestel DO male primates kill infants to improve their chances of passing on their genes? A well-established theory which says they sometimes do has been challenged by three American scientists, who call it an “almost mythological belief” with scant data to support it. The “sexual selection” theory for infanticide was proposed in the 1970s by anthropologist Sarah Blaffer Hrdy, now at the University of California at Davis. Hrdy studied the sacred monkeys of India – Hanuman langurs – and noted that males would sometimes snatch infants and wound them. Occasionally, the infants would be killed. Hrdy suggested that male langurs entering a new group try to kill off unweaned infants, who will have been fathered by another male. Female langurs remain infertile as long as they are breast-feeding. By killing unrelated young, the incoming males would free the infants’ mothers for mating. Since then, infanticide has been reported in a range of species, including other primates, lions and mice. Now Robert Sussman, James Cheverud and Thad Bartlett at Washington University in St Louis have looked again at the data for infanticide in non-human primates, and argue that there is precious little evidence to support the sexual selection theory. In all the literature on primates, they found only 48 cases of observed killings. In only eight of these cases was the male then seen to mate with the mother, the researchers add. Sussman and his colleagues believe that the killings may just be accidental. Inquisitive infant primates, they say, have a tendency to run towards the action, and could simply have been killed because they got in the way of an aggressive male whose anger was actually directed at some other animal (Evolutionary Anthropology, vol 3, p 149). The researchers also argue that proponents of the theory need to prove that the tendency to kill infants has a genetic basis, and that males killing infants actually pass on more of their genes to future generations than those who do not. “This is a nice, elegant theory. Now it has to be tested,” says Sussman. Other critics argue that some of the populations in which infanticide has been observed were crowded and disturbed by human interference, and so their behaviour might have been aberrant. Hrdy and her colleagues say that their critics are setting up unfairly high standards. No primate behaviour, they say, has a proven genetic basis. And while they agree that direct observations of infant killing may be few and far between, they say that there are many more deaths that look suspicious. Infant death rates have been seen to jump when new males enter the group, both in the wild and captivity. Furthermore, Hrdy says she has seen males stalking infants “day after day”. In future, genetic studies could help settle the argument once and for all. By genetically “typing” different animals, primatologists could be certain that males are killing unrelated infants, and could test whether infanticidal males have more offspring. This is more feasible now that DNA can be extracted from hair and animal droppings – but even so, both sides agree,

 

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