Lonesome George DNA Analysis Reveals the Secrets to Becoming a Centenarian
When Lonesome George died at the age of 102 he was considered the rarest animal on Earth. He was the last known member of his species, the Chelonoidis abingdonii — a giant tortoise native to Pinta Island, a remote fraction of the Galápagos Islands. When his caretaker of 40 years found him dead in 2012, George had died of natural causes. So what about George allowed him to live significantly longer than the average American?
Scientists explored the secrets of George’s longevity in a study published Monday in Nature Ecology & Evolution. Genetic analysis of George’s DNA, along with the DNA taken from other giant tortoises, revealed that his genetic code contained variants linked to DNA repair, cancer suppression, and a powerful immune response.
The team, made up of researchers from Yale University, the University of Oviedo, the Galápagos Conservancy, and the Galápagos National Park Service, are hopeful that learning more about George’s DNA will not only aide future conservation efforts — it will also provide insights that will bolster the study of human aging as well.
Co-author and biochemist Carlos Lopez-Otin, Ph.D., says that before this study, scientists had described nine hallmarks of aging. Now, after studying 500 more genes, Lopez-Otin announced that they “found interesting variants potentially affecting six of those hallmarks in giant tortoises, opening new lines for aging research.”
The scientists obtained DNA from blood samples taken from George prior to his death, sequenced that DNA, and compared it to genetic material taken from the related Aldabra Giant Tortoise, one of the largest tortoise species on Earth. Both species of tortoises are known for their ability to live past a century. The genomes of these tortoises revealed gene families associated with positive selection for metabolic regulation and immune response — key strengths for living long while also being large.
Cancer tumors are also very rare in giant turtles — something that the scientists note as odd because organisms that live longer lives are theoretically at a higher risk of developing cancer. To explore this conundrum, the team analyzed more than 400 genes within the tortoises’ DNA classified as oncogenes and tumor suppressors, finding that the giant tortoise genome contains duplications of the genes that suppress tumors.
The team theorizes that these genes contain mutations that block tumors from growing beyond the control of the immune system, but state that more research is needed to know for sure. With further study, they can gain a better understanding of tortoise biology, which can bolster conservation efforts.
“Our study hints at specific evolutionary strategies linked to increased lifespan, and expands our understanding of the genomic determinants of aging,” the scientists write. “These new genome sequences provide important resources to help the efforts for restoration of giant tortoise populations.”