Adaptation never stops: Study challenges long-established evolutionary theory

Oct. 19 (UPI) — Scientists in Australia claim to have debunked a long-held evolutionary theory — the assumption that in a simple, static environment, organisms will eventually reach a “fitness peak,” a plateau of adaptation, and stop evolving.

New research out of Monash University suggests there is no such thing as a fitness peak.

To better understand the molecular details of adaptation, scientists at Monash tracked the evolution of E. coli bacteria across 67,000 generations — one of the longest-running evolution experiments in science history.

The ongoing experiment has been managed by Monash scientists for the last 30 years.

“In our study we found that even though the E. coli populations in our experiment have been evolving in a very simple environment for a long time, they are still adapting to their environment,” Monash researcher Mike McDonald said in a news release. “In other words the fit get fitter.”

The findings of McDonald and his colleagues — detailed in the journal Nature — run counter to the long-held assumption of evolutionary theory.

“The established theory tells us that adaptation should have stopped by now,” McDonald said. “Our work shows that this is not the case.”

Researchers hypothesize that as the bacteria adapts, evolves and changes, it alters its environment, thus inspiring more adaptations. If true, evolution may inspire a feedback loop of never-ending adaptation.

During the experiment, researchers were able to use high-resolution genomic sequencing technology to track more than 33,000 mutations over the coarse of thousands of generations — the equivalent of more than a million years of human evolution.

Because many diseases and medical problems are adaptations gone awry, an improved understanding of the mechanics of molecular adaptations could help scientists anticipate and combat cancer and other maladies. Such knowledge could also be used to thwart the adaptive abilities of bacterial strains with antibiotic resistance, or to anticipate the impacts of climate change on vulnerable species.

“The insights we provide into the rate, repeatability, and molecular basis of adaptation will contribute to a better understanding of these evolutionary processes and challenges,” McDonald said.

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