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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]
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 ...
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. Psychological adaptations include only the functional traits that increase the ...
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.
This is an accepted version of this page This is the latest accepted revision, reviewed on 13 February 2025. Biological process of getting older This article is about ageing specifically in humans. For the ageing of whole organisms including animals, see Senescence. For other uses, see Ageing (disambiguation). Part of a series on Human growth and development Stages Gamete Zygote Embryo Fetus ...
(a) The survival rate within a population decreases with age, while the reproduction rate remains constant.(b) The reproduction probability peaks early in life, at sexual maturity, and then steadily decreases as an individual ages, with the remaining share of the population decreasing with age as they enter the selection shadow.
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]
An economic theory that defines wealth by the amount of precious metals owned. [48] business cycle. Also called the economic cycle or trade cycle. The downward and upward movement of gross domestic product (GDP) around its long-term growth trend. [49] The length of a business cycle is the period of time containing a single boom and contraction ...