Aging doesn't necessarily resemble the human pattern
Today in Nature, evolutionary biologist Owen Jones and his colleagues have published a first-of-its-kind comparison of the aging patterns of humans and 45 other species. For folks (myself included) who tend to have a people-centric view of biology, the paper is a crazy, fun ride. Sure, some species are like us, with fertility waning and mortality skyrocketing over time. But lots of species show different patterns — bizarrely different. Some organisms are the opposite of humans, becoming more likely to reproduce and less likely to die with each passing year. Others show a spike in both fertility and mortality in old age. Still others show no change in fertility or mortality over their entire lifespan.
That leftmost of the five graphs, the one that shows in its shaded area the proportion of the hydra sample that still lives, confuses me. What could possibly cause a linear decrease in population? A constant probability of death given previous survival (podgps) would produce a decreasing exponential curve, but this requires a podgps for each individual that is exactly hyperbolically growing over time, for example through an internal candleclock that is at birth set to a uniformly distributed time between 0 and 1400 years.
(Yes, hyperbolically. As the time i...
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