Promiscuity is just a case of guppy love

FAMILIARITY REALLY does breed contempt, suggests a study showing males are more likely to be sexually attracted to females they have never met before. The scientists who did the research on guppies - small tropical fish renowned for their promiscuity - reserve judgement on whether the trait is shown by humans.

FAMILIARITY REALLY does breed contempt, suggests a study showing males are more likely to be sexually attracted to females they have never met before. The scientists who did the research on guppies - small tropical fish renowned for their promiscuity - reserve judgement on whether the trait is shown by humans.

Jenny Kelley, an evolutionary biologist, and colleagues at the University of St Andrews found that male guppies showed a "Coolidge effect" when courting new females.

This was named after the former US president John Calvin Coolidge. Visiting a chicken farm in the 1920s, his wife told the farmer to tell the president that roosters mated dozens of times a day. When told that roosters mated with different hens each time, the president said: "Tell that to Mrs Coolidge."

A study published in the journal Nature has now proved the Coolidge thesis by studying guppies living in enclosed pools where males and females are familiar with each other, and comparing them with a river where males are more likely to meet female strangers.

"We predicted that males confined to pools or aquaria would direct most of their courtship towards new females, whereas males from rivers would not discriminate between females from their own school and those from a different school," the scientists say.

This is exactly what they found when they caught guppies from rivers and pools and introduced new females into their aquaria. Males from enclosed pools flocked to the new females, but males from rivers showed as much interest in the new females as the other females captured with them.

Ms Kelley would not say whether this behaviour is found in humans. "Fish and people are very different," she said.