AUSTIN, Texas -- Freeloaders can live on the fruits of the cooperation of others, but their selfishness can have long-term consequences, reports an evolutionary biologist from The University of Texas at Austin in a new study.

There is a historical dimension to cooperation, says Dr. Sam Brown, the Human Frontier Science Foundation Fellow in the Section of Integrative Biology. The act of a cooperator can continue to give benefits even after the cooperator is dead. Conversely, cheating will have consequences in the future.

Standard models of the evolution of cooperation assume that the benefits of cooperative versus selfish behavior depend only on the current abundance of cooperators in the population.

Brown has developed a new model showing that cooperators and cheaters can co-exist in a dynamic boom and bust state in the presence of long-lasting resources, known as durable goods.

Durable goods can outlast their producers, and then be passed on to future generations. They include things like antibiotics produced by populations of bacteria to kill off neighboring bacteria and public parks or buildings built by humans.

In the presence of a durable good, cheaters can increase in numbers with no immediate consequences. For example, cheaters could still enjoy the shelter of an ant nest or a building for some time even if it is not being maintained.

But freeloaders can also increase so rapidly that in a generations time the whole building collapses, says Brown.

If you have social dilemmas [where there are cooperators and cheaters] mediated by these longstanding, durable entities like buildings, ants nests, or biofilms in bacteria, then you introduce an instability, he says. Its almost as if there is a pact with the devil, because you pay nothing now for your cheating, but you pay double tomorrow, because everyones cheating and the costs come home to roost.

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Contact: Sam Brown
sam@biosci.utexas.edu
512-297-4013
University of Texas at Austin
3-Jul-2007