The extremely slow evolution of “living fossils” may affect human health

MINNEAPOLIS/ST. PAUL (03/13/2024) — The extremely slow evolution of gars, a freshwater fish species found in Minnesota’s lakes and rivers as well as in North and Central America, may provide new insights into modern human health.

The gars are from a lineage of fish that is over 150 million years old. Research recently published in Evolution reveals 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 that are often and unfairly considered trash,” said Solomon David, assistant professor at CFANS and principal investigator of the GarLab, which focuses on the ecology and conservation of native coarse fish.

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

The researchers compared rates of molecular evolution in the stations with those of more than 470 vertebrate species, many of which are 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 large animal groups, indicating that gars have the slowest rates of molecular evolution of all jawed vertebrates.
• The researchers linked the slow rates of molecular evolution to the low rates of speciation by studying the ability of the stations to produce viable, fertile hybrids between two species whose lineages split more than 100 million years ago: alligator and longnose.
• The next closest organisms that could produce viable hybrids after such a long divergence are two species of ferns that diverged more recently in evolutionary terms, 60 million years ago.

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

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

“Most cancers are somatic mutations that represent malfunctions 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 the gar DNA repair mechanisms are extremely efficient and discovers what makes them so, we can start thinking about potential applications for human health.”

David plans to create gars in his lab, contributing to genomic research with collaborators at Michigan State University and Yale University to better understand gene function and potential mechanisms for gar DNA repair. In addition, David will continue to study the population status of gar and other native coarse 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 fish provide value to our Minnesota aquatic ecosystems and even to human health.”

For the College of Food, Agriculture and Natural Resources
The University of Minnesota’s College of Food, Agriculture, and Natural Resources (CFANS) strives to inspire minds, nurture people, and sustainably improve the natural environment. CFANS has a legacy of innovation, bringing discoveries to life through science and training the next generation of leaders. Every day, students, educators, and researchers use science to address the world’s grand challenges today and in the future. CFANS offers an unparalleled variety of experiential learning opportunities for students and the community, with 12 academic departments, 10 research and outreach centers across the state, the Minnesota Landscape Arboretum, the Bell Museum of Natural History, and dozens of interdisciplinary centers. Learn more at cfans.umn.edu.