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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 classical theories of evolution (mutation accumulation, antagonistic pleiotropy, and disposable soma) [1] [2] [3] suggest that environmental factors, such as predation, accidents, disease, and/or starvation, ensure that most organisms living in natural settings will not live until old age, and so there will be very little pressure to ...
Vestigial structures are often homologous to structures that are functioning normally in other species. Therefore, vestigial structures can be considered evidence for evolution, the process by which beneficial heritable traits arise in populations over an extended period of time. The existence of vestigial traits can be attributed to changes in ...
The mutation accumulation theory of aging was first proposed by Peter Medawar in 1952 as an evolutionary explanation for biological aging and the associated decline in fitness that accompanies it. [1] Medawar used the term 'senescence' to refer to this process.
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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. At their extremes, the wide spectrum of aging theories can be ...
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] In social sciences, atavism is the tendency of reversion: for example, people in the modern era reverting to the ways of thinking and acting of a former time.
These diseases each cause changes in a few specific aspects of aging but never in every aspect at once, so they are often called "segmental progerias". [30] A 2003 report in Nature [31] said that progeria may be a de novo dominant trait. It develops during cell division in a newly conceived zygote or in the gametes of one of the parents.