JAD DAVENPORT/National Geographic
Lonesome George, the Galápagos tortoise who became famous as the sole survivor of his species, may have had a souped-up immune system, top-flight DNA repair, and increased resistance to cancer, according to an analysis of his genome.
George, the last member of the tortoise species that formerly lived on the Galápagos island of Pinta, was about 100 when he died in 2012. Researchers have now sequenced his genome and that of a giant tortoise from a different species that inhabits the Aldabra Atoll in the Indian Ocean. The results, reported today in Nature Ecology and Evolution, divulge some clues about why the reptiles can live so long.
For one thing, the immune systems of both tortoises appeared to be anything but sluggish. Mammals harbor one copy of a gene that enables immune cells to punch holes in invading or abnormal cells; the two giant tortoises carried 12 copies. George and his giant counterpart also sported a version of a DNA-fixing enzyme that may be more efficient, one of the signs that they are particularly good at mending genome damage. Duplications of two genes that may quell tumor growth, along with other genomic differences from mammals, suggest the tortoises may have evolved stronger defenses against cancer, which older animals are susceptible to. Other turtles share some of these adaptations, but some are unique to the giant species.
However, the study offers no insight into why George remained lonesome to the end, unable to father any offspring.