Testing these predictions is difficult in biological systems because it is hard to take a group of organisms that are all acting altruistic toward their relatives and experimentally give them a new ability to base altruism on genetic similarity.
"One of the great things about digital evolution is that it allows scientists to explore alternative evolutionary trajectories besides those that have already occurred on Earth," Clune said. "This experiment raises the interesting prospect that life on other planets may not revolve around familial units, but could instead be based on shared genes."
Another possibility was that organisms may choose to help only individuals who carry specific markers to indicate the presence of an "altruism gene." The mechanism, described as a "greenbeard gene," involves a conspicuous marker, such as a green beard, which indicates the presence of the altruist gene. It was theorized that in such a system all organisms with green beards would recognize and be altruistic toward each other.
Clune and his collaborators gave the digital organisms the equivalent of greenbeard genes to see if they would use them to choose who to help.
"To our surprise," said team member Heather Goldsby, "the digital organisms did not evolve to base altruism on the presence of greenbeard markers instead, they continued to rely on overall genetic similarity."
Why did the digital organisms ignore the greenbeard markers? It was discovered that the greenbeard mechanism was too inflexible: It did not allow the organisms to adjust how altruistic to be.
"The greenbeard mechanism cannot evolve to increase the minimum amount of altruism that needs to be performed to join the greenbeard club," Clune said. "For that reason, greenbeards have an incentive to do the minimal amount necessary to reap the benefits of being in the club, and no more. Unfortunately for them,
|Contact: Tom Oswald|
Michigan State University