Oxford, LSU, Tulane research questions aspect of Darwin theory

The Red-billed Scythebill (Campylorhamphus trochilirostris), a woodcreeper from the ovenbird family. Credit: Joseph A. Tobias
The Red-billed Scythebill (Campylorhamphus trochilirostris), a woodcreeper from the ovenbird family. Credit: Joseph A. Tobias

It’s considered the bedrock of the theory of evolution, but after more than 150 years, researchers at Oxford University in England, LSU and Tulane University have poked a hole in one aspect of Charles Darwin’s “Origin of Species.”

It was once thought that similar species living near each other evolved in order to avoid competition. Oxford researchers, with an assist from LSU, are now saying that’s not always the case.

Evolution theory, which is regarded as fact by the mainstream scientific community, says populations evolve over the course of multiple generations through the process of natural selection.

Natural selection is the idea that many more individuals were born that could be supported by the environment, meaning some had to die. The ones that died were those least well adapted to the environment. The idea is also known as “Evolve or Die.”

Darwin’s book, published in 1859, further says species living together in close proximity evolve differently to avoid competing with each other.

Take birds for example. Multiple species of birds can live together in a rainforest and eat many of the same insects, without coming into direct competition for food.

In the study published in Nature, a respected journal of science, however, the international research team found data that shows differences in a family of birds evolved long before the community was formed.

That finding isn’t opening the door for the creationism argument.

Robb Brumfield, director of LSU’s Museum of Natural Science and curator of the museum’s Collection of Genetic Resources, is quick to point out the study is not questioning the validity of the theory of evolution.

“Any time you have the word ‘evolution,’ you have the possibility that it starts up the creationism debate,” Brumfield said. “But with this research, that doesn’t apply.”

The study is saying evolution is still valid but it’s not entirely clear why it happens.

“It may just be random how these species evolved or, at least, it’s poorly understood how that happened,” Brumfield said. “This is just a very small part of the Origin of Species.”

This particular study looked at 350 species of ovenbirds, one of the most diverse bird families in the world.

The research was made possible through more than 30 years of expeditions where scientists lugged nitrogen tanks to some of the most remote places in the world to collect tissue samples from birds before freezing them in liquid nitrogen for further study.

Many of those materials are housed in Baton Rouge, where LSU has more than 62,000 tissue samples and 175,000 bird skins, known as specimens, tucked away in the basement of Foster Hall.

It was through those samples and specimens that researchers were able to “reconstruct the tree of life for different birds,” Brumfield said.

In layman’s terms, researchers used DNA analysis to construct family trees of bird species to map out how and when they branched out from one species into numerous others.

Brumfield said a scientist walking into one small part of a rainforest can observe distinct species of ovenbirds living near each other but exhibiting vastly different behaviors.

Woodcreepers, for instance, hunt for insects by pecking at tree bark. Leaftossers forage for insects on the ground, while foliage-gleaners find their food on tree leaves.

“Darwin says these differences evolved to avoid confrontation. We reconstructed the tree of life for different birds, and we saw when the different species evolved,” Brumfield said. “Their differences pre-date their co-occurrences.”

Joe Tobias, of Oxford University’s Department of Zoology, led the research.

“It’s not so much a case of Darwin being wrong, as there is no shortage of evidence for competition driving divergent evolution,” he said in the study’s findings. “But we found no evidence that this process explains differences across a much larger sample of species ... we found that most ovenbird species only meet their closest relatives several millions years after they separated from a common ancestor. This gives them plenty of time to develop differences by evolving separately.”

In addition to scientists from Oxford, LSU and Tulane, researchers from Lund University in Sweden and the American Museum of Natural History in New York, also contributed to the study.

Visit www.lsu.edu/researchnews for more information.