Have scientists discovered reverse evolution? Study shows how house dust mites have abandoned their parasitic lifestyle to become free-living just like their ancestors

When it comes to evolution, there has always been the deep-rooted belief that you can't go backwards.
But new research has been published which challenges the idea that evolution is only moving forward in one direction. 
The study was conducted by two scientists at the University of Michigan who carried out a genetic study of the common house dust mite.

Devolution: Two scientists from the University of Michigan carried out the study on the house dust mite

According to Dollo's law, a theory proposed in 1893 by French-born Belgian paleontologist Louis Dollo, evolution is 'unidirectional and irreversible. 
But this new study shows that tiny free-living house dust mites, which thrive in mattresses, sofas and carpets in even the cleanest of homes, evolved from parasites, which 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 in several habitats, including human habitations,' according to Pavel Klimov and Barry O'Connor.

Their study, called 'Is permanent parasitism reversible? Critical evidence from early evolution of house dust mites,' was published in the journal Systematic Biology.

Dollo's law was formulated by Louis Dollo, a French-born Belgian paleontologist

Mites are arachnids related to spiders, both have eight legs, and are among the most diverse animals on Earth. 
House dust mites, members of the family Pyroglyphidae, are the most common cause of allergic symptoms in humans, affecting up to 1.2 billion people worldwide.
Despite their huge impact on human health, the evolutionary relationships between these speck-sized creatures are poorly understood. 
According to Klimov and O'Connor, there are 62 different published hypotheses arguing about whether today's free-living dust mites originated from a free-living ancestor or from a parasite - an organism that lives on or in a host species and damages its host.
In their study, Klimov and O'Connor evaluated all 62 hypotheses. 
Their project used large-scale DNA sequencing, the construction of detailed evolutionary trees called phylogenies, and sophisticated analyses to test the hypotheses about the ancestral ecology of house dust mites.
The result was so surprising largely because it runs counter to the entrenched idea that highly specialized parasites cannot return to the free-living lifestyle of their ancestors.
The findings also have human-health implications, said O'Connor, a professor in the Department of Ecology and Evolutionary Biology and a curator of insects and arachnids at the University of Michegan Museum of Zoology.
The project started in 2006 with a grant from the National Science Foundation. 
The first step was to obtain specimens of many free-living and parasitic mites which was a hard task given that some mite species are associated with rare mammal or bird species around the world.
The research team relied on a network of 64 biologists in 19 countries to obtain specimens. 
In addition, Klimov and O'Connor conducted field trips to North and South America, Europe, Asia and Africa. 
On one occasion, it took two years to obtain samples of an important species parasitizing African birds.
A total of around 700 mite species were collected for the study.