Evolutionary Entropy Shapes Lifespan of the Greenland Shark

The Greenland shark (Somniosus microcephalus) is among the longest-lived vertebrates known, with female maturity estimated at about 156 years and maximum ages approaching four centuries. We use the entropic theory of life histories and an open-group Leslie model to determine which reproductive windows are compatible with this extreme demographic profile. The model yields generation times, reproductive quantiles and entropy-maximizing reproductive endpoints. A critical value of reproductive persistence, $q_c\approx 0.9763$ , separates two regimes: below it, evolutionary entropy increases towards an asymptote; above it, entropy is maximized at a finite reproductive endpoint. Longevity-calibrated scenarios lie on both sides of this threshold and imply generation times near or above two centuries, with reproductive contributions extending into the third, fourth and fifth centuries of life. As an independent benchmark, an empirically parametrized Leslie model for the bowhead whale yields comparable entropy-based demographic quantities while allowing the reproductive and survivorship parameters to be calculated directly. The method provides quantitative constraints on reproductive organisation in exceptionally long-lived species for which detailed demographic data are unavailable.