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Why is it that less than 5 per cent of mammal species are monogamous, compared with about 90 per cent of bird species?
Hazel Russman
London, UK
This is a consequence of what is known as Trivers’s cruel bind, named after the evolutionary biologist Robert Trivers.
A male animal that impregnates a female leaves her literally holding the baby. She then has to raise any infants to the best of her ability because they might represent her entire genetic investment for the year. The male is free to go off and impregnate other females, increasing his contribution to the…
