Sexual infidelity 'may be anti-social'

In contrast, staying faithful appears to promote cooperative behaviour.

The evidence comes from bird species which vary in their levels of promiscuity.

Among those with faithful females, chick-rearing duties are often shared between non-parent relatives. This did not occur when female birds had numerous male partners.

A link between low levels of promiscuity and social behaviour had previously been seen in ants, bees, wasps, termites and shrimps, but not vertebrates.

The researchers believe it could generally apply across a whole range of species, even humans.

"There is no reason why promiscuity rates couldn't account for the distribution of social systems in mammals, including primates," said study leader Dr Ashleigh Griffin, from the Department of Zoology at Oxford University.

"Sex, at least in evolutionary terms, is an antisocial force."

The scientists reported their findings in the journal Nature.