February, 2005:
quotes from the article:
The Avida team makes their software freely available on the Internet, and creationists have downloaded it over and over again in hopes of finding a fatal flaw. While they’ve uncovered a few minor glitches, Ofria says they have yet to find anything serious. “We literally have an army of thousands of unpaid bug testers,” he says. “What more could you want?”
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Bringing diversity into Avida has brought more bad news for those who think complexity cannot evolve. Ofria decided to run the complexity experiment over again, this time with a limit on the supply of numbers. “It just floored me,” he says. “I went back and checked this so many ways.” In the original experiment, the organisms evolved the equals routine in 23 out of 50 trials. But when the experiment was run with a limited supply of numbers, all the trials produced organisms that could carry out the equals routine. What’s more, they needed only a fifth of the time to do it.
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Human society depends on countless acts of cooperation and personal sacrifice. But that doesn’t make us unique. Consider Myxococcus xanthus, a species of bacteria that Lenski and his colleagues study. Myxococcus travels in giant swarms 100,000 strong, hunting down E. coli and other bacteria like wolves chasing moose. They kill their prey by spitting out antibiotics; then they spit out digestive enzymes that make the E. coli burst open. The swarm then feasts together on the remains. If the Myxococcus swarm senses that they’ve run out of prey to hunt, they gather together to form a stalk. The bacteria at the very top of the stalk turn into spores, which can be carried away by wind or water to another spot where they can start a new pack. Meanwhile, the individuals that formed the stalk die.
This sort of cooperation poses a major puzzle because it could be undermined by the evolution of cheaters. Some bacteria might feast on the prey killed by their swarm mates and avoid wasting their own energy making antibiotics or enzymes. Others might evolve ways of ensuring that they always end up becoming spores and never get left behind in the dead stalk. Such cheaters are not theoretical: Lenski and his colleagues have evolved them in their lab.
The Avida team is now trying to address the mystery of cooperation by creating new commands that will let organisms exchange packages of information. “Once we get them to communicate, can we get them to work together to solve a problem?” asks Ofria. “You can set up an information economy, where one organism can pay another one to do a computation for it.”
If digital organisms cooperate, Ofria thinks it may be possible to get them working together to solve real-world computing problems in the same way Myxococcus swarms attack their prey. “I think we’ll be able to solve much more complex problems, because we won’t have to know how to break them down. The organisms will have to figure it out for themselves,” says Ofria. “We could really change the face of a lot of computing.”ooOoO00
Ofria has been finding that digital organisms have a way of outwitting him as well. Not long ago, he decided to see what would happen if he stopped digital organisms from adapting. Whenever an organism mutated, he would run it through a special test to see whether the mutation was beneficial. If it was, he killed the organism off. “You’d think that would turn off any further adaptation,” he says. Instead, the digital organisms kept evolving. They learned to process information in new ways and were able to replicate faster. It took a while for Ofria to realize that they had tricked him. They had evolved a way to tell when Ofria was testing them by looking at the numbers he fed them. As soon as they recognized they were being tested, they stopped processing numbers. “If it was a test environment, they said, ‘Let’s play dead,’ ” says Ofria. “There’s this thing coming to kill them, and so they avoid it and go on with their lives.”
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More: http://devolab.cse.msu.edu/
The Evolutionary Origin of Complex Features: R.E. Lenski, C. Ofria, R.T. Pennock, and C. Adami in Nature (2003), pages 139-145.
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