Evolution in reverse: How did mites get less specialized?
But the microscopic dust mite also turns out to be a peculiar example of evolution “in reverse”—or more precisely, despecialization—according to a new study by University of Michigan biologists Pavel Klimov and Barry OConnor. And this counters a long-held assumption in evolutionary biology known as Dollo’s law (after the 19th-century Belgian paleontologist Louis Dollo), which stipulates that once you gain a complex trait, you can’t return to the simpler states of your distant ancestors.
This poses a conundrum in the mite world. The distant ancestors of dust mites evolved to be able to feed directly on a bird or mammal—to become parasitic and therefore more complex. So how did the free-living dust mites get to be free living, and thus less complex? There were 62 different hypotheses in the academic literature trying to answer this question. …
But the result was clear. “The authors have made a compelling case that free-living dust mites evolved from a parasite, thus providing another counterexample to Dollo’s law,” says Jeff Gore, a biophysicist at the Massachusetts Institute of Technology who did groundbreaking work on bacterial evolution. As Klimov explains, “we found that very specialized organisms like parasites can drastically become despecialized.”