Cambridge, MA - July 15, 2009 - This year marks the the 200th anniversary of Charles Darwin's birth. And while The Origin of the Species remains the bedrock of modern evolutionary theory, scientists still cannot agree how the tremendous diversity of life came to be. A new study published in this week's Nature magazine comes closer to settling the debate. The study's authors demonstrate that diverse species can arise just from the arrangement of organisms across an area, without any influence from geographical barriers or even natural selection.
In recent years, two views of the process of "speciation" have come to dominate evolutionary theory. One requires a physical barrier such as a a glacier, mountain, or body of water to separate organisms, enabling groups to diverge until they become separate species. In the second, an environment favors distinct characteristics within a species, encouraging divergence as members fill different roles in an ecosystem. Other ideas have been discussed but never considered to account for more than a few special cases.
However the researchers of this week's article have developed a computer model that shows the formation of diverse species is possible even without physical boundaries or distinct niches in the ecosystem. The study found that over generations the genetic distance between organisms in different regions increases, and groups of organisms spontaneously form groups that can no longer mate, causing a patchwork of species across the area. The number of species increases rapidly until it reaches a relatively steady state.
"One can think about the creation of species on the genetic level in the same way we think about the appearance of many patterns, including traffic jams," said Yaneer Bar-Yam, President of The New England Complex Systems Institute. "While the spatial environment may vary, specific physical barriers aren't necessary. Just as traffic jams can form from the flow of traffic itself without an accident, the formation of many species can occur as generations evolve across the organisms' spatial habitat."
Particularly intriguing is the fact that the simulation showed the distribution of species formed patterns similar to those that have occurred with real organisms all around the globe.
"Compared to prior simulations, this single theory matches a never before seen range of species data," said Marcus de Aguiar, a collaborator on the project. "It's supported by data from both animals and plants, both around the world and throughout time. We found it matched years worth of data observed by British bird watchers, data from an exhaustive study of Panamanian shrubs and trees, records of ray-finned fish populations, North American songbirds, marine invertebrate fossils and the mammal fossils of Kansas."