A super efficient genome, thanks to a robust DNA repair system: this is the secret of living fossils, as animal species are defined that have remained practically unchanged for tens of millions of years, such as the coelcanth and the alligator gar.
The discovery, which could open a new way to fight tumors, is published in the journal Evolution and is due to research coordinated by Thomas Near of Yale University.
Charles Darwin coined the expression 'living fossil' in 1859 to indicate organisms that still seem perfectly identical to their ancestors who lived millions of years ago and whose testimony is told by fossils.
The best known of these is probably the coelacanth, a fish whose oldest fossils date back to 390 million years ago.
The mystery of these species lies in the fact that, despite having been subjected to tens of millions of years of evolutionary pressure through mutations and selection, they seem to have remained almost identical, while most other species have changed much more rapidly.
To try to solve the puzzle, the researchers analyzed the DNA of 12 living fossils to measure the rate of mutations in different individuals.
It thus emerged that what has allowed great stability to the species is a mechanism, still little known, capable of repairing any mutations very precisely.
Of the 12 species analysed, the one with the most advanced protection mechanism turned out to be the alligator gar, a species of which fossils dating back to 150 million years ago are known and whose DNA mutates three times more slowly than in other species.
If this hypothesis were confirmed it could also have important implications for medicine because "most tumors - said Near - are somatic mutations that represent failures of an individual's DNA repair mechanisms".
According to the researcher, "if we discovered what makes the pike's repair mechanisms efficient, we could start to think about potential applications for human health."
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