Saturday, April 05, 2008

Darwinism looks to explain collective behavior

Wired has a great article on what the next frontier, or hurdle if you will, is for the explanatory power of modern neo-Darwinism — the development of groups and collectives. This includes bees in a hive, ants in a colony, bacteria in a collective, and even more complex things such as the vast array of bacteria that make up 90 percent of the cells in our own “human” bodies.

The main question is, how can neo-Darwinian theory as currently constituted explain these developments of evolutionary biology — if it can?

Down in front, creationists and IDers. Wired is a serious magazine and isn’t asking for “explanations” from you.

But, some of the evolutionary biologists quoted in the story say that something, either a greatly modified neo-Darwinianism or else some appended theory of emergent properties, based on things like chaos theory, complexity theory, and the “tipping points” popularized by Malcolm Gladwell, is going to be needed to do the trick.
”There’s nothing wrong with neo-Darwinian evolution in its own right,” Carl Woese said, “but it’s not large enough to encompass what we know now.”

Woese’s specialty is bacteria, and he’s not afraid of bold theories that turn conventional scientific wisdom on its head. In 1977, he and colleague George Fox rearranged the animal kingdom from five branches into three, two of which comprise microbes.

Microbes make up much of Earth’s biomass, and they also cast into relief the shortcomings of neo-Darwinian evolution. A bucket of seawater can contain 60,000 bacterial species, and to Woese, these must be seen as a collective rather than as disparate units.

At the collective level, said Woese, bacteria exhibit patterns of organization and behavior that emerge suddenly, at tipping points of population variation and density called “saltations.” Natural selection still favors — or disfavors — the ultimate outcome of these jumps, but the jumps themselves seem to defy explanation solely through genetic changes or individual properties.

Such jumps don’t just call into question whether evolution is capable of producing sudden rather than gradual change. That debate raged during the later stages of the last century, but has been largely settled in favor of what paleontologists Niles Eldredge and Stephen Jay Gould termed punctuated equilibrium. By contrast, Woese invokes yet-to-be-quantified rules of complexity and emergence. These, he said, may also explain other exceptional jumps, such as the transition from protein fragments to single cells and from single-celled organisms to multicellular ones.

Contrary to IDers, creationists, or New Agers, etc., Woese works with rules that have a basis in science and/or mathematics, rules that are ultimately testable through construction of hypotheses.

Part of the issue hinges on debate over an idea stated most forcefully by philosopher Daniel Dennett: Is neo-Darwinism algorithmic or not? I am guessing Woese would either say “I don’t know,” or “possibly not.” Other evolutionary biologists might agree with Dennett, yet others might reject his claim forcefully.
”Selection probably happens at all scales, from gene to individual to species to collection of species to ecosystem to we don’t even know what,” said Maya Paczuski, head of the Complexity Science Group at the University of Calgary.

Paczuski’s group sees evolution as taking place at all these levels, with what happens in ecosystems rippling down to individuals, back up to populations, across to other populations, and so on — all simultaneously, and in tandem with the mysterious dynamics of networked complexity.

But does it all happen mechanically? Or does evolution obey some larger imperative?

University of Nevada evolutionary biologist Guy Hoelzer calls that imperative biospheric self-organization. "The idea of evolution is embedded within self-organization,” he said. “It coordinates the ecological roles of species so that ecosystems persist and process a great deal of energy.”

I, too, doubt Dennett’s idea, though as a scientific layperson (but not a philosophical one), I don’t think I have enough of a scientific background to be able to reject it forcefully. I do think that, to some degree, the developmental processes we eventually discover in the emergent properties of biological groups, collectives and ecosystems will show enough discontinuity with neo-Darwinism to be likely to develop as separate subfield within evolutionary biology.

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