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The Mathematics of the Lifespan of Species
skade88 writes "NPR is reporting on a study in which the author claims to have found the formula to predict the average life span of members of a species. It does not apply to specific individuals of that species, only to the average life span of members of the species as a whole. From the article: 'It's hard to believe that creatures as different as jellyfish and cheetahs, daisies and bats, are governed by the same mathematical logic, but size seems to predict lifespan. The formula seems to be nature's way to preserve larger creatures who need time to grow and prosper, and it not only operates in all living things, but even in the cells of living things. It tells animals for example, that there's a universal limit to life, that though they come in different sizes, they have roughly a billion and a half heart beats; elephant hearts beat slowly, hummingbird hearts beat fast, but when your count is up, you are over.'"
There are so many exceptions to this "rule" that it is at best an interesting pattern. There are big turtles that live great long lives and big turtles that don't with little turtles being all over the place as well. There are birds of all kinds of sizes with small birds that live 80 years and big birds that live under 20. Some bacteria seem to be nearly immortal and others live days. Within dogs the big ones hardly outlast green bananas while the little ratty ones go on for decades. Poplar trees grow huge and die fast, oaks go on and on but some smaller trees are thousands of years old.
Even humming birds live a few years at crazy heartbeats as high as 1200 bpm (look it up if you don't buy that mind blowing number) yet other bigger birds with much slower heart beats live for the same length of time. So it isn't size or heartbeats.
If I had to suspect anything lifespan will be an evolutionary advantage like anything else. If you are surrounded by ever changing dangers a short fast life-cycle is probably best. But if you are fairly safe in steady environment a long life is probably safer. Turtles have slow metabolisms which allow them to survive long periods without food and are fairly safe from predictors so they don't have to worry about adapting too much. Rabbits are basically the forest's McNuggets so they need to continuously adapt in numbers and probably other things such as coloring; hence a fast short life cycle. We have created civilization where we are nearly 100% safe from predators and with things like food storage are not so buffeted by a changing nature; so we are getting longer an longer lived.