Reading path: Types of sharks →
A closer look at the evidence
| Question or feature | Explanation | What it does not establish |
|---|---|---|
| Eye-lens core | Early-forming proteins turn over very little, preserving a radiocarbon record. [1] | Radiocarbon and calibration still require a model to infer calendar age. [2] |
| Largest sampled female | 502 cm; modeled age 392 ± 120 years, with a 95.4% probability range. [2] | The approximate 272–512 range is not a directly observed age or lifespan maximum. [2] |
| Study sample | Lens-core radiocarbon was analyzed from 28 female sharks. [2] | Does not independently establish male longevity or ages for all sharks of a given size. [2] |
| Maturity estimate | Female maturity was estimated at at least about 156 years, with reported 22-year uncertainty. [2] | An estimate, not a precise age applying to every female or a lifespan value. [2] |
The tissue behind the age estimate
The Greenland shark (Somniosus microcephalus) is a slow-growing cold-water shark studied in the Arctic and North Atlantic. Its exceptional longevity is supported by a specific measurement approach: a 2016 study analyzed radiocarbon in the nuclei of eye lenses from 28 female sharks. These measurements provided evidence about when lens material formed; they did not directly reveal a shark’s birthday. [1] [2]
Lens-core proteins form early and undergo very little turnover, so the core can preserve a chemical record unlike tissues that are continuously renewed. This persistence makes the lens useful for age inference. Vertebrae in this species do not provide the usual clear calcified growth marks, which is one reason researchers used the lens method. [1]
The researchers also used the radiocarbon pulse associated with nuclear testing to help distinguish younger sharks from older, pre-bomb animals. Most of the sampled sharks lacked the elevated bomb-era signal found in the smallest individuals. That pattern is part of the evidence, not a direct calendar label attached to each shark. [2] [1]
What “392 years” means
The largest sampled female measured 502 centimetres and had a modeled age estimate of 392 years, with uncertainty of 120 years on either side. The study expressed the estimates as a midpoint and the extent of a 95.4 percent probability range. In plain arithmetic, 392 ± 120 gives an approximate range of 272 to 512 years for that animal under the model. [2]
That range is not a set of observed ages. Calling the shark “512 years old” would report the upper end as a known age and hide both the midpoint and uncertainty. Nor is 512 a demonstrated maximum lifespan for the species: it is the upper edge of an estimate for the largest female in this sample. [2]
The distinction resembles reporting a measurement with its uncertainty rather than selecting the largest plausible value. The midpoint communicates the model’s central estimate; the interval communicates how far the inferred age may extend. Neither turns an inferred age into an observed birthday. The study supports exceptional longevity while requiring that uncertainty remain attached to the number. [2] [1]
From chemical signal to calendar age
Radiocarbon dating depends on calibration and on the carbon incorporated into the tissue being measured. Lens measurements therefore require a model to infer calendar age from the chemical signal. The nuclear-testing pulse helps identify whether tissue formed before or after that signal, but the pulse alone does not produce a complete age for every shark. [2] [1]
A useful evidence-reading exercise is to separate three steps: a laboratory measurement of lens-core radiocarbon, interpretation of that signal against the nuclear-testing pulse and calibration, and a modeled age with a probability range. If a report skips the last two steps and presents a single number as directly counted years, it overstates what this method measures. [2]
The source material also makes a sample boundary clear: 28 females were studied. Their results do not independently establish male longevity, and they do not mean that every Greenland shark of a given size has the same age. The largest sampled animal’s length and age estimate belong together as a specific observation and model output, not a universal size-to-age conversion. [2]
Maturity is another estimate, not a lifespan
The study estimated female maturity at a very late age, at least about 156 years, with a reported 22-year uncertainty. This is a separate biological estimate from the age assigned to the largest sampled female. It speaks to when females may reach maturity under the study’s analysis; it does not set a species-wide lifespan or provide an exact maturity age for every individual. [2]
A late maturity estimate, slow growth and the evidence of centuries-long ages together describe a life history with long timescales. Still, each claim answers a different question: lens radiocarbon supports age inference, the maturity estimate concerns reproductive timing, and the 502-centimetre measurement describes the largest sampled female. Combining them is informative only if the distinctions stay visible. [2] [1]
The strongest summary is therefore measured and specific: radiocarbon from the lens cores of 28 females supports exceptional longevity in Greenland sharks, and the largest sampled female’s modeled estimate was 392 years with a broad interval. The evidence does not establish a directly observed birthday, male age distribution or definitive maximum lifespan. [2]
Sources & further reading
Have a correction or a source to suggest? Send a note →