Study of ‘Living Fossils’ Reveals Remarkably Slow Evolution, Offering Insights for Human Health

The remarkably slow evolution of gars, freshwater fish species found in Minnesota lakes and rivers as well as North and Central America, could provide new insights for modern human health.

Gars are from a lineage of fishes that is over 150 million years old. Research recently published in Evolution, uncovers evidence of a biological mechanism for living fossils like gars, those organisms alive today that closely resemble their fossil ancestors.

“We have a lot to learn from animals often, and unfairly, considered trash fish,” said Solomon David, an assistant professor in CFANS and principal investigator of GarLab, which focuses on the ecology and conservation of native rough fish.

Led by Yale University,  the team includes researchers from the University of Minnesota, University at Buffalo, Chinese Academy of Sciences in Beijing and the University of Southern Mississippi.

The researchers compared rates of molecular evolution in gars to those of over 470 vertebrate species, many of them often considered living fossils, including crocodiles, turtles, sharks and coelacanths.

The research found:

• Gar DNA evolves up to three orders of magnitude slower than other major animal groups, indicating gars have the slowest molecular evolution rates among all jawed vertebrates.
• Researchers linked slow rates of molecular evolution to low rates of speciation, studying the ability of gars to produce viable, fertile hybrids across two species, whose genera split over 100 million years ago: alligator gar and longnose gar.
• The next closest organisms that could produce viable hybrids after such a long divergence are two species of ferns that separated more recently in evolutionary terms, 60 million years ago.

The team speculates that gars have an unusually efficient DNA repair mechanism, correcting alterations to DNA more efficiently than most other vertebrate groups. This mechanism may be responsible for low species diversity, hybridization across long-diverged genera, and overall slow rates of evolution.

Identifying the mechanism for this strong DNA repair could also have implications for medical research and human health.

“Most cancers are somatic mutations that represent failures of an individual’s DNA repair mechanisms,” said Tom Near, a professor at ​​Yale University and senior author of the study. “If further study proves that gar DNA repair mechanisms are extremely efficient, and discovers what makes them so, we could start thinking about potential applications to human health.”

David plans to spawn gars in his lab, contributing to genomics research with collaborators at Michigan State University and Yale University to better understand gene function and potential gar DNA repair mechanisms. Additionally, David will continue studying the population status of gars and other native rough fish in Minnesota ecosystems, a priority of the Minnesota Department of Natural Resources.

“True living fossils exist and can give us new insights into evolution and biodiversity,” said David. “These unique native fishes provide value to our Minnesota aquatic ecosystems and even human health.”