Senescence

Hydras are a genus of simple, freshwater animals that do not undergo senescence, and, as such, are biologically immortal.

Many animals have one or more tissues that are self-renewing, e.g. the skin of humans. These tissues consist of stem cells with a large or indefinite capacity for cell division. In humans only some of our bits have this stem cell driven renewal capacity whereas in hydras all tissues are self-renewing, that is all of their cells are part of one or another stem cell system.

It would appear to me that population control is taken care of by evolution. Birth, death, accidents, starvation and predators – all these things must be balanced to allow for short-term and long-term variations and stability in population control and survival.

A small handful of organisms, like the hydras, go for the rather eccentric solution to this set of kinetic equations, i.e. extremely long life. Probably because they have an unusual set of kinetic inputs (e.g. unlimited food or an ability to hibernate, no predators – not even themselves, a choice of sexual and asexual reproduction, etc).

The ‘thermodynamic’ driving forces behind the kinetic solutions for all organisms on this planet must be the same, i.e. abstracted and closed-system limiting cases of the physical thermodynamic laws of enthalpy and entropy.

(Therefore the governing equations for life of each organism are like a set of Fokker-Plank equations).

Humans, of course, are trying to figure out how hydras do it in order to copy them. I can guarantee you that if we are successful then our goose is cooked on this planet.