Evolution is Reversible, New Study on Dust Mites Shows

First Posted: Mar 09, 2013 04:12 PM EST

Reverse evolution is possible, a new study on house mites – of all things – has revealed.

The mainstream scientific belief has always been that evolution was an unidirectional mechanism – that is, once organisms develop new evolutionary traits, they don’t get to go back to their previous state. This idea has been so pervasive in the scientific community that it has even made into law – the Dollo’s law: "that evolution is not reversible; i.e., structures or functions discarded during the course of evolution do not reappear in a given line of organisms.” The hypothesis was first advanced by a historian, Edgar Quinet.

However, a new study conducted by a research team led by two biologists from University of Michigan seems to challenge this long held belief. The research carried on common house mites that live on mattresses, sofas and carpets shows that certain organisms can undergo reverse evolution.

According to the study, these mites have evolved from parasites that have in turn evolved from free-living organisms millions of years ago.

"All our analyses conclusively demonstrated that house dust mites have abandoned a parasitic lifestyle, secondarily becoming free-living, and then specialized in several habitats, including human habitations," according to Pavel Klimov and Barry OConnor of the U-M Department of Ecology and Evolutionary Biology.

The scientists discovered that the mites have gone back to the ways of their ancestors by beginning to live independently; a phenomenon which contradicts the idea that evolution only moves forward.

"This result was so surprising that we decided to contact our colleagues to obtain their feedback prior to sending these data for publication," said Klimov, the first author of the paper and an assistant research scientist in the Department of Ecology and Evolutionary Biology.

The phylogenetic tree of the mites showed that the mites' close relatives are the Psoroptidia, which are full-time residents in the bodies of birds and animals. Also, the immediate ancestor of the mice in carpets and mattresses are the mites that live in the fur of dogs and cats.

"Parasites can quickly evolve highly sophisticated mechanisms for host exploitation and can lose their ability to function away from the host body," Klimov said. "They often experience degradation or loss of many genes because their functions are no longer required in a rich environment where hosts provide both living space and nutrients. Many researchers in the field perceive such specialization as evolutionarily irreversible."

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