Genome of 194-year-old tortoise Jonathan reveals 287 unique variants and youthful mitochondrial genes

Genetic analysis of a bicentenarian giant tortoise

Scientists from an international research team have mapped the genome and epigenome of Jonathan, a 194-year-old Seychelles giant tortoise recognized as the world's oldest living land animal. The findings, published on 7 October 2026 in the journal Science Advances, describe molecular mechanisms that prevent cellular decay across nearly two centuries of life. Researchers collected DNA samples through mouth scrapings and saliva swabs to avoid invasive procedures on the protected animal. The study team, led by Benjamin Vaisvil alongside researchers from institutions across the United States, the United Kingdom, Denmark, and Germany, compared Jonathan's genetic material against four other Aldabra giant tortoises of varying ages. The sequencing identified 287 distinct genetic variants present exclusively in Jonathan, covering biological pathways tied to DNA repair, inflammation reduction, insulin regulation, telomere protection, and cancer suppression.

Mitochondrial stability and epigenetic patterns

Beyond individual sequence variants, the study examined DNA methylation, which consists of chemical tags that regulate gene activity over time. While methylation patterns across most of Jonathan's genome resembled those of typical older tortoises, the markers on genes governing mitochondrial function matched the profiles of young animals. Mitochondria generate cellular energy, and their progressive breakdown is a primary biological driver of aging and degenerative illness in animals. Study co-author Justin Gerlach from the University of Cambridge described how energy regulators in the tortoise maintained their operational integrity.

We found that the genetic regulators involved in energy production and DNA repair have remained incredibly stable in Jonathan for nearly two centuries.

Senior study author Stephen Clark, a neuro-oncologist at the Kallel Foundation and former Vanderbilt University faculty member, noted that maintaining pristine cellular power generation offers fundamental insights into organismal survival.

We're still trying to work out how ageing occurs and Jonathan gives us a real window on to what happens over a long period of time. His mitochondria must be especially stable and that's an insight into longevity in general. It's important that the mitochondria are kept as pristine as possible.

Life at Plantation House on Saint Helena

Jonathan is a specimen of Aldabrachelys gigantea hololissa, a subspecies of the Aldabra giant tortoise native to the Seychelles. Historical records indicate he hatched around 1832 and was transported across the South Atlantic Ocean to Saint Helena in 1882 as a gift for future governor Sir William Grey-Wilson. The tortoise was approximately 50 years old upon arrival and has resided on the grounds of Plantation House for 144 years. Despite complete blindness and typical age-related ailments, Jonathan remains in good health under veterinary supervision. On 1 April 2026, false death claims circulated on social media before being dismissed as a fraudulent fundraising scheme.

Future clinical trials and longevity research

Researchers at the Nashville-based Kallel Foundation plan to use the genetic findings to design intervention studies focused on human longevity. The next phase of research seeks to test whether stabilizing or replacing cellular mitochondria can prolong healthy lifespan in laboratory settings. Stephen Clark stated that the non-profit aims to evaluate generic pharmaceutical compounds that showed positive outcomes during prior animal testing. Clinical trials investigating these mitochondrial preservation strategies could begin as early as next year if sufficient research capital is secured.

We want to do clinical trials that no drug company wants to do.