Why female mammals live longer than males but female birds die first

Scientists have found that while lifestyle and environment are important, genes also play a part

Male and female Eurasian bullfinch (Pyrrhula pyrrhula). The inheritance mechanism in birds is the opposite of the mammal one. It’s the female who is ‘heterogametic’ — she has both a W and a Z chromosome. Male birds with their second Z, therefore, are less prone to suffer mutation damage than females. And so they live longer.

‘For no man at all can be living for ever, and we must be satisfied’ — Maurya in Riders to the Sea

The heroine of JM Synge’s 1896 play, set in Inishmaan, has lost her husband and five sons to the sea. News arrives that a body has been washed up in Donegal. The clothing shows it’s that of Michael, another son. Bartley, the last of Maurya’s boys, is sailing to Connemara to sell a horse. He too perishes; a ghost-rider has been seen. "They’re all gone now," says the grief-stricken mother, "and there isn’t anything more the sea can do to me".