Richard Pallardy is a freelance science writer based in Chicago. He has written for such publications as National Geographic, Science Magazine, New Scientist, and Discover Magazine.
Gars are the ultimate living fossils, having changed at an incredibly slow pace since their ancestors emerged during the dinosaur age 150 million years ago, scientists have revealed. This leisurely rate of change means these prehistoric fish have the slowest rate of molecular evolution among all jawed vertebrates.
The term is contentious because while many such species resemble their fossil relatives, they have actually undergone evolutionary changes, even if they are not immediately evident. To be a living fossil, an organism needs to have ancient common ancestry with extinct lineages, have changed little in physical form from fossil relatives and diversified into a relatively small number of related species, lead author Chase Brownstein, a first year graduate student at Yale, told Live Science.
Substitutions result in physical changes. The low rates of substitution in this group of fish thus correspond to low rates of speciation — meaning the lineage has not diversified into huge numbers of new, physically distinct species as other groups have. Instead, the few species that have emerged have remained stable over long periods.
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