Selfishness 'can sometimes help the common good'

Researchers in Europe analysed populations of yeast and found that a mixture of "cooperators" and "cheats" grew faster than a more utopian one of only "cooperators".

For their study, the researchers from Imperial College London, Bath University, Oxford University, University College London and Max Planck Institute for Evolutionary Biology used laboratory experiments and a mathematical model to understand why and how a little "selfishness" can benefit the population.

In the study, the "cooperator" yeast produce a protein called invertase that breaks down sugar (sucrose) to give food (glucose) that is available to the rest of the population. The "cheats" eat the broken down sugar but don't make invertase themselves, and so save their energy.

Lead researcher Prof Laurence Hurst of University of Bath said: "We found that yeast used sugar more efficiently when it was scarce, and so having 'cheats' in the population stopped the yeast from wasting their food.

"Secondly we found that because yeast cannot tell how much sucrose is available to be broken down, they waste energy making invertase even after there is no sugar left. This puts a brake on population growth. But if most of the population are 'cooperators' and the remainder are 'cheats', not all of the population is wasting their energy and limiting growth.

"For these effects to matter, we found that 'cooperators' needed to be next to other 'cooperators' so they get more of the glucose they produce. If any of these three conditions were changed, the 'cheats' no longer benefitted the population."

Added co-researcher Ivana Gudelj of Imperial College London: "Our work illustrates that the commonly used language of 'cooperators' and 'cheats' could in fact obscure reality.

"When the addition of more invertase producers reduces the fitness of all, it is hard to see invertase production as cooperation even if it behaves in a more classical cooperative manner, benefitting all, when rare."

The findings are to be published in an upcoming issue of the 'PLoS Biology' journal.