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The two theories; non-adaptive, and adaptive, are used to explain the evolution of senescence, which is the decline in reproduction with age. [8] The non-adaptive theory assumes that the evolutionary deterioration of human age occurs as a result of accumulation of deleterious mutations in the germline. [8]
Arrows show the vestigial structure called Darwin's tubercle. In the context of human evolution, vestigiality involves those traits occurring in humans that have lost all or most of their original function through evolution. Although structures called vestigial often appear functionless, they may retain lesser functions or develop minor new ones.
The vestigial versions of the structure can be compared to the original version of the structure in other species in order to determine the homology of a vestigial structure. Homologous structures indicate common ancestry with those organisms that have a functional version of the structure. [15]
Biogerontology should not be confused with geriatrics, which is a field of medicine that studies the treatment of existing disease in aging people, rather than the treatment of aging itself. There are numerous theories of aging, and no one theory has been entirely accepted.
Aging is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. The hallmarks of aging are the types of biochemical changes that occur in all organisms that experience biological aging and lead to a progressive loss of physiological integrity, impaired function and, eventually, death.
A number of traits can vary as a result of shortening of the fetal development of a trait or by prolongation of the same. In such a case, a shift in the time a trait is allowed to develop before it is fixed can bring forth an ancestral phenotype. [5] Atavisms are often seen as evidence of evolution. [6]
Genetics of aging is generally concerned with life extension associated with genetic alterations, rather than with accelerated aging diseases leading to reduction in lifespan. The first mutation found to increase longevity in an animal was the age-1 gene in Caenorhabditis elegans .
A psychological adaptation is a functional, cognitive or behavioral trait that benefits an organism in its environment. Psychological adaptations fall under the scope of evolved psychological mechanisms (EPMs), [ 2 ] however, EPMs refer to a less restricted set.