The study confirms it evolved only once

May 13, 2010 10:58 GMT  ·  By

For many years, researchers have been hypothesizing that it may have been possible for life to appear and develop several times. Basing their idea on the fact that the natural world shows countless examples in which the same ability evolves in different species through different mechanisms, the researchers argued that the same conditions that led to the original emergence of life may have repeated themselves. However, a new statistical analysis demonstrated beyond a reasonable doubt that this was not the case, and that all lifeforms on our planet indeed share a common origin, Wired reports.

According to Brandeis University biochemist Douglas Theobald, one of the most important provisions of the theory of evolution is the fact that life evolved from a single source. In fact, the expert adds, this idea is a “central pillar of evolutionary theory. But recently there has been some mumbling, especially from microbiologists, that it may not be so cut-and-dried.” The researchers set out to get his facts straight after hearing other scientists argue that that the tree of life may be more of a web. This belief was prompted by the fact that microorganisms tend to swap genes, even if they belong to different species.

This led some to say that originally there was more than one primordial lifeform. All of these structures may have contributed in equal amounts to the development of life per se. This would indeed mean that life on Earth is a web, not a tree featuring a single root. Theobald decided to investigate which of these two ideas held more merit. In order to do that he applied extremely rigorous statistical testing to a number of evolutionary ancestry models, belonging to both “camps.” In a paper appearing in the May 13 issue of the esteemed scientific journal Nature, the expert reveals that the research yielded considerable more evidence for the single-ancestor model than for any others.

Theobald's calculations show that chances of life having developed from a single source are about 102,860 times higher than it having emerged from multiple sources. “ In one sense, we are not surprised at the answer, but we are very pleased that the unity of life passed a formal test,” explains Massey University Allan Wilson Center researcher and theoretical biology expert David Penny. In an accompanying essay to the paper, he and colleague Mike Steel, who is based at the University of Canterbury, say that this is the first time such a rigorous batch of tests has been applied to the theory.

“The universal common ancestor (models) didn’t just explain the data better, they were also the simplest, so they won on both counts,” Theobald reveals. The model “doesn’t tell you where the deep ancestor was. But what it does say is that there was one common ancestor among all those little beasties,” Penny concludes.