August 24, 2010

Living Space, Not Competition, Evolutionary Catalyst

The amount of available living space--not competition, as Darwin believed--may have been the catalyst of evolution, according to a new study published in the August 23 edition of Biology Letters.

As part of the study, researchers at the University of Bristol analyzed the fossils of birds, mammals, reptiles, and amphibians dating as far back as 400 million years ago. According to BBC News science reporter Howard Falcon-Lang, "the scientists showed that the amount of biodiversity closely matched the availability of 'living space' through time."

"The new study proposes that really big evolutionary changes happen when animals move into empty areas of living space, not occupied by other animals," Falcon-Lang said, noting that birds developed the ability to fly in order to gain access to areas not open to other animals, and that the extinction of dinosaurs helped mammals by creating more open space.

"This concept challenges the idea that intense competition for resources in overcrowded habitats is the major driving force of evolution," the BBC News reporter added.

"Competition did not play a big role in the overall pattern of evolution," professor and study co-author Mike Benton told Falcon-Lang. "For example, 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."

However, Yale University Professor Stephen Stearns had a different view of their findings, telling BBC News that he "found the patterns interesting, but the interpretation problematic."

"To give one example, if the reptiles had not been competitively superior to the mammals during the Mesozoic, then why did the mammals only expand after the large reptiles went extinct at the end of the Mesozoic?" he added. "And in general, what is the impetus to occupy new portions of ecological space if not to avoid competition with the species in the space already occupied?"

On his return to England in 1836, Darwin tried to solve the riddles of these observations and the puzzle of how species evolve. Influenced by the ideas of Malthus, he proposed a theory of evolution occurring by the process of natural selection. The animals (or plants) best suited to their environment are more likely to survive and reproduce, passing on the characteristics which helped them survive to their offspring. Gradually, the species changes over time.

According a biography posted online at the's history page, Darwin's theory of natural selection states that biological life forms are more likely to survive and reproduce when they are well-suited to their environments, and adaptations occur over time in order to help organisms adapt and thrive. The Shrewsbury-born naturalist began working on his theory in 1836, and ultimately published his landmark book "On the Origin of Species" in 1959.


On the Net: