London, May 31 : Scientists at the University of Leeds have reignited the contentious debate about why hundreds of species of insects and other animals evolved altruistic behaviour to put the interests of the colony over the individual, by finding that they do so to increase the chances that their genes will be passed on.
For the study, the team led by William Hughes, of Leeds University, UK, studied the orthodox theory of 'kin selection,' which says that an animal may pass on its genes by helping relatives to reproduce, because they share common genes, rather than by reproducing itself.
The concept of 'kin selection' was developed in 1964 by the evolutionary biologist William Hamilton, reports New Scientist.
But this paradigm was challenged in 2005 by the eminent academic E.O. Wilson, the founder of sociobiology, who pointed out that relatedness is rather low in some of today's social insects.
He suggested that highly social behaviour evolves solely because individuals do better when they cooperate than when they live a solitary life - a controversial theory which not only conflicted with 45 years of scientific research, but which also sparked a highly charged debate between Wilson and Richard Dawkins, author of The Selfish Gene.
Dr Hughes and colleagues at the Universities of Sydney and Sussex tested the two alternative theories by examining the level of relatedness between females in colonies of bees, wasps and ants, determined by DNA fingerprinting techniques, and using statistical methods to look at levels of monogamy in the ancestral social insects when they evolved up to 100 million years ago.
If females were monogamous, mating with one male, this would mean the members of the colony are highly related, and so Hamilton's theory would be correct.
If they were polygamous, with the female mating with many males, relatedness would be lower and so Wilson may be right after all.
The research found that in every group studied ancestral females were found to be monogamous, providing the first evidence that kin selection is fundamental to the evolution of social insects.
Dr Hughes said: "We have produced the first conclusive evidence that kin selection explains the evolution of social insects and that Wilson's hypothesis is most probably wrong."
"By challenging something that we have based all our understanding on for 45 years, Wilson has forced us all to examine the theory again and assess the logic of the arguments. In a recent media interview, he issued a challenge to the scientific community to prove his theory wrong and whilst many felt it was, there hasn't been any hard evidence until now."
Hughes contents that these results would seem to settle the longstanding debate revived by Wilson.
The study is published in the journal Science.