Giant tortoises have been a staple of the Galapagos and can live up to 100 years in captivity. Lonesome George may have been the last of his species, Chelonoidis abingdonii, but he has provided an insight into the genetics of longevity. Genetic analysis of DNA from Lonesome George and samples from other giant tortoises were found to possess a number of gene variants linked to DNA repair, immune response, and cancer suppression not possessed by shorter-lived vertebrates. The tortoises’ slow metabolism and large size tend to correlate well with long life and infrequent reproduction.
Decline Of The Giant Tortoise Population
These large creatures began disappearing after the arrival of humans in the Galapagos since they were hunted for their oil and meat. Two centuries of exploitation caused the loss between 100,000 to 200,000 tortoises. It’s estimated that only 20,000 – 25,000 live on the islands today.
Tortoises tend to move slowly, leaving them open for hunters and breed too infrequently to compensate for the loss. A female tortoise can lay 1-4 nests over their nesting season (June to December). The number of eggs varies but can range from 20-25 eggs for domed tortoises.
This number may seem like a lot but their eggs and young are easy prey for other species like rats and birds. Lonesome George’s species population size has been in decline for about one million years. However, this is expected for a large species confined to a small island that reproduces slowly.
The Secret Of Tortoise DNA
Adalgisa “Gisella” Caccone, the senior researcher in Yale’s Department of Ecology and Evolutionary Biology and co-senior of the research, began sequencing the whole genome of Lonesome George to study the evolution of the tortoise population on the Galapagos in 2010.
The data was then analyzed by Carlos Lopez-Otin at the University of Oviedo in Spain in order to find gene variants that are usually associated with longevity. He explained that they “had previously described nine hallmarks of aging and after studying 500 genes on the basis of this classification, they found interesting variants potentially affecting six of those hallmarks in giant tortoises, opening new lines of aging research.”
Although the genetics of longevity has been explored in long-lived mammals, extending to tortoises should illuminate general hallmarks of the genetic basis of longevity.
New Lines Of Aging Research
These new details of the giant-tortoise genomes could shed light on aspects of the peculiar evolution and development of tortoises, such as their shell. Duplications of genes involved in DNA repair have also been noted to be related to longevity and exists in not only giant tortoises but also several other species.
However, these lessons about the longevity of tortoises should not be applied to the human species without some form of caution. The longevity of any species is the blueprint of who they are and their entire life’s history. The research surrounding giant tortoises is not over and according to Caccone, “Lonesome George is still teaching us lessons.” It will be interesting to see where Lonesome George will lead us next.