A Strange-Looking Fish, Frozen In Time

A group of fish called gar, dubbed “living fossils,” may have the slowest rate of evolution of any jawed vertebrate.

The term “living fossil” has been applied to any number of animals, from sharks to turtles to the coelacanth. It’s the idea that those animals look very much the same way their species may have looked millions of years ago, with limited evolutionary change over that time.

After analyzing the genomes of many different species on that “living fossil” list, researchers report they may have found an animal that evolves more slowly than all the others—a group of fish called gar. The rate of molecular change in gar genomes is the slowest of any jawed vertebrate, the researchers say. In fact, gar genomes change so slowly that two gar species that diverged from each other over 105 million years ago can still interbreed and produce fertile offspring. In evolutionary time, that’s comparable to the distance between humans and elephants. The researchers believe that the slow rate of change in gars may be due to an exceptional ability to repair mutations and other errors in their genes.

Dr. Solomon David, assistant professor of aquatic ecology at the University of Minnesota, and Chase Brownstein, a graduate student in Yale’s department of ecology and evolutionary biology, join Ira to discuss the findings, recently reported in the journal Evolution.

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