In humans and many other animals, males age faster and die earlier than females. Now scientists think they may have discovered why – sex.

Males in monogamous species such as the dwarf mongoose tend to survive as long as females (credit Miika Silfverberg (MiikaS), Finland)

Scientists at the University of Cambridge compared monogamous species with polygynous species, in which each male mates with many females. Males in monogamous species, such as the barnacle goose or the dwarf mongoose, naturally compete less over females than ones in polygynous species, such as the savannah baboon.

Researchers Tim Clutton-Brock and Kavita Isvaran found the more polygynous a species was, the more likely their males were to age faster and die earlier than females. The researchers explained that as competition among males for sex grows more intense, each male on average has less time to breed. As such, there is no strong incentive to evolve longevity among males in such species.
The team think that their findings relate to humans as men age faster and die earlier than women.

Clutton-Brock, Prince Philip Professor of Ecology and Evolutionary Biology, said: “At the time when current human physiology evolved, perhaps around the late Stone Age, polygynous breeding was the norm. Of course, this doesn’t provide any justification for polygyny or promiscuity now for males.”

Clutton-Brock and Isvaran detailed their findings in the journal Proceedings of the Royal Society B.