Old age is the last stage of human life, in which the physical and psychological deterioration associated with cell death is clearly experienced. This is not innate to the entire animal kingdom, since the most fortunate species do not suffer any decline with age and are capable of reproducing until the moment of death . New research from the University of Southern Denmark suggests that this ability to stay forever young challenges evolutionary theories, which claim that aging is an intrinsic trait of each species.
Although the life of many small fish and water fleas lasts for only a few days, their mortality increases with age, as is the case with most long-lived human-like animal species. There are, however, other species that challenge some evolutionary theories by not experiencing any deterioration as the time of their death approaches .
The group of scientists analyzed the lifespan of 46 different animal species with respect to their life expectancy. The results revealed that there was no link between the length of life and the degree of senescence in some species, such as the hermit crab, the red abalone or the hydra, a microscopic freshwater animal that can live for centuries . Such a diversity of aging strategies challenges the notion that evolution inevitably leads to senescence, or the decline in mortality and fertility with age.
However, some experts are critical of the work , and doubt that it compromises evolutionary theories, as it is limited by the wide variety of causes of death that have not been considered (predation or disease, for example) and that occur more often than natural death.
