These gars are remarkable examples of ‘living fossils’.

 The concept of "living fossils," coined by Charles Darwin in 1859, refers to species that have maintained similar characteristics for millions of years, raising questions about whether they have evolved little or just resemble their ancestors. A recent study published in Evolution reveals that some living fossils, particularly gars, exhibit a remarkably slow rate of molecular evolution due to their effective DNA repair mechanisms. Gars, ancient-looking fish, have the slowest rates of molecular evolution among jawed vertebrates, with some species diverging very little even after more than 100 million years. The study gathered genetic data from various species and found that while some living fossils like coelacanths and the hoatzin bird have slightly faster mutation rates, gars stand out for their exceptionally slow evolution.

The study suggests that gars' ability to repair DNA efficiently has kept their genomes stable over millions of years, preventing significant genetic changes despite environmental shifts. Other factors contributing to gars' slow evolution include their slow metabolic rates, long generation times, preserved chromosome arrangements, and reduced impact of genetic rearrangements. Surprisingly, the study also found that gars from two different genera, having split 20 million years ago, shared nearly identical sequences in their DNA, showcasing their minimal genetic divergence. Moreover, researchers observed natural hybridization between two gar genera that diverged over 100 million years ago, leading to fertile offspring and breaking records for the oldest split among eukaryotes capable of producing viable hybrids.

The team's findings not only shed light on the mechanisms behind living fossils' lack of genetic change but also have potential implications for understanding human DNA repair pathways and diseases like cancer. Future research may involve investigating the specific DNA repair mechanisms in gars by introducing gar genes into zebrafish models, although this presents challenges due to the fundamental nature of DNA repair genes. Overall, the study underscores the importance of studying species like gars to unravel the mysteries of evolution and genetic stability over vast timescales.

In conclusion, "These gars are the ultimate 'living fossils'" study provides valuable insights into the fascinating world of ancient species and their unique evolutionary strategies that have allowed them to persist virtually unchanged for millions of years. The research opens up new avenues for exploring the mechanisms behind genetic stability and has broader implications for understanding the complexities of evolution and DNA repair mechanisms in both ancient organisms and humans. [Source: https://www.science.org/content/article/these-gars-are-ultimate-living-fossils]