( Selfishness is not necessarily the best...)Survival of the selfless - scientists find cheats don't always prosper

Writing in the journal Nature today, the team reports that studies of lab-grown yeast populations suggest the benefits of cheating are eventually counterbalanced by the costs. This contradicts classic evolutionary theory, which states that in a competition for common resources the long-term winner will always be the individual acting selfishly rather than the one working as part of a group.

To test this theory, scientists set up a series of competitions between two strains of yeast. The strains are identical apart from the genes that determine whether they convert energy from resources such as sugar rapidly or if they convert it efficiently.

In one corner were the 'cooperators', which produce energy efficiently by taking in sugar slowly and fully converting into energy all that they ingest. This method maximises resources available to the group by avoiding any waste.

Against them were the 'cheaters', which produce energy rapidly by quickly taking in all the sugar they can and only partially converting it into energy. While this ensures swift energy production for the individual, it is a wasteful method that reduces resources available for the group as a whole.

The researchers were surprised to find that in a well-mixed population the cooperators were not excluded by the cheats. Further experiments and mathematical modelling established that this is because cheats accumulate toxins as a direct result of taking in resources more quickly than they can digest them, which limits the level of energy they derive from the sugar. This enables the cooperators to hold their own, meaning that the two different strains could coexist over the long-term without either being excluded. Lead researcher Dr Craig MacLean of Imperial College London says: