Researchers at the University of Michigan said in a study published on Friday that house dust mites are living evidence against the popular theory that organisms cannot reverse their own evolutionary process.

"All our analyses conclusively demonstrated that house dust mites have abandoned a parasitic lifestyle, secondarily becoming free-living, and then speciated in several habitats, including human habitations," said Pavel Klimov and Barry O'Connor in the study, published in the journal Systematic Biology.

According to Science Daily, Klimov and O'Connor's research indicated that dust mites evolved from parasitic organisms known as skin mites, commonly found on livestock, cats and dogs. The skin mites are themselves descended from independent lifeforms millions of years ago.

The two biologists collected 700 mite species for their study, which used large-scale DNA sequencing, statistical analyses and reconstructed evolutionary trees to evaluate 62 different theories regarding dust mites' origins.

Klimov said their findings were surprising, given that, according to Dollo's law, evolution can only move forward over time. In the case of parasites, he said, they can often lose the ability to function independently as they become better-equipped to feed off of the resources available thru their host lifeforms.

"[Parasites] 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," he said. "Many researchers in the field perceive such specialization as evolutionarily irreversible."

According to Klimov and O'Connor's study, dust mites were able to use some of their ancestors' traits -- increased weather tolerance and adaptability in seeking hosts, and the development of enzymes allowing them to eat more kinds of biological material -- to gradually wean themselves off of living exclusively off any given host.

[Image of house dust mites via Wikipedia Commons]