Was Darwin Wrong? An Alternative Theory Emerges

(Aug. 26) -- Until now, Charles Darwin's concept of survival of the fittest and natural selection has been considered the key to the evolution of all living things.

But a new study by researchers at the University of Bristol in England and published in Biology Letters suggests "living space," not competition between species, is responsible for evolutionary patterns throughout history.

Using fossils to focus on land animals, the research team suggests that animals have survived more easily in favorable environments that offered more food and less chance of being hunted and eaten by other animals.

At Yale University in Connecticut, evolutionary biologist Stephen Stearns isn't convinced by the study findings.

"They have an interesting pattern, but I think they misinterpreted it. Basically, what they show is that a lot of evolution is driven by organisms moving into new roles or onto land or into new areas, and they argue that that's evidence that competition is not so important," Stearns told AOL News.

Stearns, the author of "The Evolution of Life Histories" (Oxford, 1992), says it doesn't make sense for animals to just pack up and move from one environment to another.

"Why would they move if everything was comfortable where they were? So, competition probably is one of the things that drove them into the new environment," he said.

"It's a trade-off: 'Should I stay here and deal with what I've got here, or should I go somewhere else?' Well, going somewhere else is always a challenge, because wherever you have been, you're always pretty well adapted to that, and the only reason to go somewhere else is if the conditions here are deteriorating."
One of the authors of the British study, Mike Benton, told the BBC that "competition did not play a big role in the overall pattern of evolution."

"Even though mammals lived beside dinosaurs for 60 million years, they were not able to out-compete the dominant reptiles. But when the dinosaurs went extinct, mammals quickly filled the empty niches they left and today, mammals dominate the land."

But Stearns says the pattern the British researchers have documented isn't sufficient evidence to determine what actually caused the pattern.

Over time, he said, "conditions are probably going to be deteriorating because other organisms are evolving to be better at extracting resources from your environment than you are, or they're evolving to be better at eating you.

"I think they overinterpreted their results when they claimed that they can conclude that competition wasn't driving it."

Stearns explains the concept of "living space" doesn't only relate to a location or a physical place where animals live.

"When you're talking about 'living space,' it's not really geography -- it's like, what role do you play in the community? You can't really have squirrels until you have trees. That's what they mean by 'living space.'"

While Stearns and the British researchers don't see eye to eye, he welcomes the study because it fuels scientific debate. And because evolution is an ongoing, long process, he believes the study will add to scientific knowledge.

"It will have a standard academic impact, and there will be some critical commentary and other people will see if they can actually replicate the results -- scientists don't usually believe a result until it's been independently replicated, and that hasn't happened yet.

"I think that after it has been criticized and sifted and we know what parts of it stand up, it might become a textbook example. It might, but we don't know yet."