A PNAS study led by researchers at The University of Tokyo has produced a nearly complete genome for the Greenland shark, the longest-lived vertebrate known to science. The assembly covers 96.7 percent of its genetic material and reveals several features that could help its cells endure for centuries.
The team found genetic signatures associated with DNA maintenance, immune activity, cancer resistance and the packaging of chromosomes. Researchers also identified unusual changes in a protein called histone H1.0. Computer predictions suggest that these changes could stabilize the shark’s genetic material against damage.
These clues offer a molecular view of an animal whose life unfolds at an almost unimaginable pace. A large Greenland shark swimming today may have entered the Arctic Ocean centuries before modern genetics, steam power, or industrial medicine existed.
A lifespan measured in centuries
The Greenland shark, or Somniosus microcephalus, inhabits deep and cold waters across the North Atlantic and Arctic. It grows slowly and can reach lengths of several meters. Much of its life passes far from sunlight in an environment where low temperatures help shape its exceptionally slow biology.
Scientists established the species’ remarkable longevity through a 2016 study in Science. Julius Nielsen and his colleagues estimated the ages of 28 female sharks by analyzing proteins in the lenses of their eyes. Those proteins form early in life and remain chemically stable, which allows them to preserve evidence from the animal’s birth period.
The researchers used radiocarbon dating to estimate when those eye-lens proteins formed. Their largest shark was assigned an estimated age of 392 years with an uncertainty of 120 years in either direction. The results established a lifespan measured in centuries and placed the species beyond other known vertebrates for longevity.
Greenland sharks also appear to mature at an extraordinary age. Estimates suggest females may reach sexual maturity at around 150 years. Slow growth and delayed reproduction make the species especially sensitive to deaths caused by fishing or other disturbances.
Mapping 5.9 billion DNA letters
The University of Tokyo team assembled a Greenland shark genome containing about 5.9 billion DNA base pairs. That total is close to twice the size of the human genome. The sequence was organized at chromosome scale with an N50 length of 233 million base pairs, a measure of how continuous the assembled sections are.
According to the study abstract, “Here, we report a chromosome-level assembly of the Greenland shark genome.” The researchers combined modern sequencing approaches to build long stretches of DNA and determine how those stretches fit together inside chromosomes.
The final chromosome-level genome assembly reached a completeness score of 96.7 percent. This level of coverage gives scientists a detailed reference for identifying genes and examining how genetic regions changed during the shark’s evolution.
A high-quality assembly also allows meaningful comparisons with related animals. The team examined the Greenland shark alongside the Pacific sleeper shark and other shark species. These comparisons can reveal gene families that expanded, contracted, or accumulated distinctive changes within the Greenland shark lineage.
Genetic clues to cellular endurance
Living for centuries creates a demanding biological problem. DNA experiences damage through ordinary chemical reactions, cellular metabolism and copying errors. Mutations can accumulate as cells divide. Proteins may lose their shape, while inflammation and other forms of cellular stress can gradually disrupt tissues.
Long-lived animals need effective ways to preserve cellular function across many decades or centuries. In the Greenland shark genome, the researchers detected features linked to DNA repair, immune enhancement and cancer resistance. Each system could contribute to survival by controlling a different source of molecular damage.
DNA repair proteins find damaged sections of genetic material and help restore the correct sequence. Tumor-suppression systems monitor cells for dangerous changes. Immune pathways remove threats and coordinate responses to injured tissue. The balance among these systems may be especially important for an animal with such a long potential lifespan.
The study’s genetic associations remain starting points for laboratory work. Researchers will need to test the shark’s proteins in cells and compare their activity with equivalent proteins from shorter-lived species. Those experiments could reveal which changes have substantial effects and how they work together.
Histone H1.0 may protect the genome
One of the most intriguing findings concerns histone H1.0, a protein involved in organizing DNA. A cell stores its long strands of DNA by wrapping and folding them into a compact structure called chromatin. Histones help create and maintain that structure.
The Greenland shark carries unique amino acid substitutions in the rounded central region of histone H1.0. Computer modeling predicts that these substitutions may strengthen chromatin stability. Tightly managed chromatin can help shield DNA and regulate access to genes.
Stable packaging could become valuable over a lifespan that extends through several human centuries. It may reduce opportunities for damaging molecular interactions and help cells preserve the organization of their chromosomes. This proposed benefit still requires direct functional testing.
Chromatin also affects which genes become active in a cell. Changes to histone behavior could therefore influence DNA protection and gene regulation at the same time. The shark’s version of H1.0 gives researchers a specific molecule for experiments on cellular durability.
Expanded defenses against damage
The 2026 analysis found gene-family changes involving established longevity pathways. These included genes associated with immune function, resistance to cancer and the repair of damaged DNA. The genome also contains an expanded family related to iron storage.
A gene called FTH1b was present in unusually high copy numbers. It contributes to ferritin, a protein complex that stores iron inside cells. Managing iron matters because free iron can promote chemical reactions that damage membranes and other cellular structures.
Other expanded families were associated with the NF-κB signaling pathway. This network helps regulate inflammation, immune responses and cell survival. Its activity requires careful control because inflammation can protect tissues during injury while persistent activation can contribute to long-term damage.
A separate genome project led by Arne Sahm reported preliminary findings on the bioRxiv preprint server in September 2024. That international team described a genome rich in transposable elements, which are DNA sequences capable of copying or moving within the genome. Its analysis proposed that these elements may have helped duplicate genes involved in DNA repair.
The 2024 preprint identified 81 repair-related genes that appeared duplicated in the Greenland shark while remaining single-copy genes in the other sharks examined. As a preprint, that work represents an early analysis awaiting the full scrutiny associated with peer review. It offers a complementary hypothesis about how extensive genome duplication may have supported stronger cellular maintenance.
A possible link to ferroptosis
Iron storage connects the Greenland shark genome to another research question. The PNAS team highlighted a potential relationship between the shark’s distinctive gene repertoire and ferroptosis, a form of regulated cell death driven by iron-dependent damage to fatty cell membranes.
Cells must keep iron available for essential chemistry while preventing it from triggering destructive reactions. Ferritin helps maintain that balance by storing iron in a controlled form. The expansion of FTH1b may therefore influence how Greenland shark cells respond to oxidative stress and membrane damage.
Ferroptosis has drawn attention in research on cancer, aging and neurodegenerative disease. Its possible role in the shark remains a hypothesis generated from genome comparisons. Experiments will be needed to measure iron handling and ferroptosis directly in Greenland shark cells.
This line of investigation could reveal how multiple protective systems interact. Iron storage, inflammation, DNA maintenance and cell death pathways all influence tissue health. The shark’s extreme lifespan may emerge from the combined effects of several molecular defenses.
Limits of the age estimates
The famous 392-year figure includes a wide range of uncertainty. The largest shark in the 2016 analysis was estimated to be 392 years old plus or minus 120 years. That range reflects the difficulty of dating animals that lack common age markers such as annual growth bands in hard tissue.
Radiocarbon dating also depends on changes in atmospheric carbon over time. Nuclear weapons testing during the 1950s and 1960s produced a distinct radiocarbon signal that helps identify younger animals. Dating sharks born centuries earlier requires calibration against older environmental records.
The evidence supports a lifespan extending for several centuries. The exact maximum remains open to refinement as scientists develop improved dating methods and examine more specimens. Even the lower portion of the estimated range places the Greenland shark among Earth’s most extraordinary vertebrates.
Similar care applies to the genomic findings. Gene expansions and unusual protein sequences can generate strong biological hypotheses. Their influence on lifespan becomes clearer through cell experiments, protein studies and comparisons across animals with different longevities.
What the discovery means for aging research
The Greenland shark genome gives scientists a new reference for exploring how evolution can preserve an animal for centuries. Researchers can now compare its genes with those of bowhead whales, giant tortoises, naked mole rats and other species known for long lives.
Each lineage may emphasize a different combination of protective mechanisms. The Greenland shark points researchers toward chromatin stability, iron control, immune regulation and genome maintenance. Studying those systems together could provide a broader picture of biological aging.
For human aging research, the immediate value lies in identifying molecules and pathways that deserve closer examination. The shark’s proteins can be recreated in laboratory systems and tested for effects on DNA protection or cellular stress. Researchers can also investigate whether similar mechanisms already operate in people.
Direct medical applications would require years of functional studies and safety testing. Human cells operate within a very different metabolism and body plan. A mechanism suited to a cold-water shark may produce different effects in human tissue.
The genome also has value beyond longevity. It can support research into shark evolution, deep-sea adaptation, population history and conservation. For an animal that may spend hundreds of years moving through Arctic darkness, its DNA now offers a detailed record of survival across an exceptional span of time.
