Research directions
Facts, patterns and records
Collect consequential facts about ageing, look for patterns and test which hypotheses fit them.
Facts to compare
A record with uncertainty. The largest Greenland shark in a 2016 study was estimated at 392 ±120 years, with a 95.4% probability interval, using eye-lens radiocarbon dating.
A cross-species pattern. Across 16 mammalian species, longer lifespan was associated with fewer new mutations per year in intestinal crypt cells. Crypts are recesses in the intestinal lining.
An experimental result. Removing intestinal DAF-2 nearly doubled worm lifespan under the study conditions. Comparisons with other interventions require the protocol and original survival data.
Keep the evidence that every explanation must fit
Longevity records show the range that biology can achieve. Population patterns reveal how that range is organised. Experimental results show what has changed under intervention. Keeping these kinds of evidence distinct makes it possible to compare claims and see what a new result actually adds.
What to investigate
Separate maximum lifespan, median lifespan, age-specific mortality and time lived in good health.
Record species, sex, husbandry, sample size, controls and the method used to estimate age.
Retain uncertainty intervals, negative results and independent replications alongside the headline finding.
Evidence to build on
Nielsen and colleagues used eye-lens radiocarbon dating in Greenland sharks. For the largest sampled animal, they estimated an age of 392 years with an uncertainty of ±120 years, reported as a 95.4% probability range. This is an age estimate from a model, with its uncertainty retained.
What remains unresolved
An exceptional animal establishes a documented observation, while typical survival needs population data. Comparisons across species also require attention to age estimation and the conditions in which animals lived.
The next useful experiment
Audit a striking longevity claim from the original measurements to the final estimate, then test whether it holds with another method or independent sample.
Proposed experimentsThe wider strategy
The presentation uses survival experiments as the basis for comparing interventions. This approach provides the common evidence record on which those comparisons depend.
The Death-Fighting Spectrum presentation