These gars are the ultimate ‘living fossils’

In 1859 Charles Darwin coined the term “living fossil” to describe lineages that have looked the same for tens of millions of years, such as the coelacanth, sturgeon, and horseshoe crab. The term captured the popular imagination, but scientists have struggled to understand whether such species just resemble their long-ago ancestors or have truly evolved little over the eons. Now, in a study published today in Evolution , researchers confirm that in some–but not all—living fossils, evolution is at a virtual standstill . The most striking examples are prehistoric-looking fish called gars, which have the slowest rate of molecular evolution of all jawed vertebrates. The team also proposes a mechanism to explain gars’ timelessness: superb DNA repair machinery. That repair has likely kept gar genomes so stable that species and even genera whose last common ancestor lived more than 100 million years ago have diverged very little, and some can still hybridize today to produce viable offspring. “That’s amazing,” says Tetsuya Nakamura, an evolutionary developmental biologist at Rutgers University who was not involved in the work. “This paper has a lot of interesting work into this question of what makes a living fossil, but when I read that, I was shocked.” To see whether several putative living fossils evolve more slowly than other vertebrate groups, the team gathered published sequences from more than 1100 exons (the...
Source: Science of Aging Knowledge Environment - Category: Geriatrics Source Type: research