The Elements of Evolution (51-5) Aging & Mortality

Aging & Mortality

Many people, including scientists, think that aging is inevitable and occurs in all organisms on Earth as it does for humans: that every species becomes weaker with age and more likely to die. That is not the case. ~ American evolutionary biologist Owen Jones

Aging and mortality (rates of death) among the tree of life are an extreme example of divergent evolution. Some organisms don’t age but succumb at widely varying rates. Others age and die in deviating ways. Some species with pronounced aging (that is, those with sharply rising mortality rates) live a long time, whereas others don’t.

Humans and some other mammals weaken as they age, with rising mortality. By contrast, some plants and many animals have a rather constant mortality throughout their lives, regardless of lifespan.

Many flora and some fauna, such as the desert tortoise, experience the highest mortality early in life, with a steadily declining rate thereafter. Many of these organisms suffer no loss of vitality with age as humans do.

Species with very different life spans can display similar patterns of mortality, fertility and survivorship. ~ German demographer Alexander Scheuerlein et al