Study of slowly evolving ‘living fossils’ reveals key genetic insights

March 4, 2024

Yale researchers have discovered evidence of why a fish group, considered “living fossils,” has existed largely unchanged for tens of millions of years. 

In 1859, Charles Darwin coined the term “living fossils” to describe organisms that show little species diversity or physical differences from their ancestors in the fossil record. In a new study, Yale researchers provide the first evidence of a biological mechanism that explains how living fossils occur in nature.

The study, published in the journal Evolution, shows that gars - an ancient group of ray-finned fishes that fit the definition of a living fossil - have the slowest rate of molecular evolution among all jawed vertebrates, meaning their genome changes more slowly than those of other animals.

By linking this finding to the process of hybridization - when two different species produce viable offspring - of gar species in the wild that last shared common ancestry during the age of the dinosaurs, the researchers demonstrate that slow evolution rate of their genome drives their low species diversity.

“We show that gars’ slow rate of molecular evolution has stymied their rate of speciation,” said Thomas J. Near, professor of Ecology and Evolutionary Biology in Yale’s Faculty of Arts and Sciences and the paper’s senior author. “Fundamentally, this is the first instance where science is showing that a lineage, through an intrinsic aspect of its biology, fits the criteria of living fossils.” 

For more information, click here for an article published by Yale News or here for an article published by Science.org.

News & Updates

Edward P. Bass Distinguished Lecture: The World Without Evolution? with Andrew Hendry

April 23, 2025
Dear YIBS community, Please join us in attending the Edward P. Bass Distinguished Lecture: The World Without Evolution? with Andrew Hendry Date: Wednesday, April 23rd from...
Noah Planavsky

Nonprofit built on research from YIBS Faculty Affiliate Noah Planavsky wins global carbon removal prize

April 23, 2025
Normally, throwing rocks at a problem isn’t the best idea. But in the multi-faceted fight to combat climate change, scientists are finding that crushed rocks judiciously...
Mixodectes pungens, small mammals that inhabited western North America 62 million years ago, weighed about 3 pounds, dwelled in trees, and largely dined on leaves. Illustration by Andrey Atuchin

A 62-million-year-old skeleton sheds light on an enigmatic mammal

March 11, 2025
For more than 140 years, Mixodectes pungens, a species of small mammal that inhabited western North America in the early Paleocene, was a mystery. What little was known about...