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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 ...
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 existence of vestigial organs can be explained in terms of changes in the environment or modes of life of the species. Those organs are typically functional in the ancestral species but are now either semi-functional, nonfunctional, or re-purposed. Scientific literature concerning vestigial structures abounds.
Convergent evolution—the repeated evolution of similar traits in multiple lineages which all ancestrally lack the trait—is rife in nature, as illustrated by the examples below. The ultimate cause of convergence is usually a similar evolutionary biome , as similar environments will select for similar traits in any species occupying the same ...
Another possibility is that a trait may have been adaptive at some point in an organism's evolutionary history, but a change in habitats caused what used to be an adaptation to become unnecessary or even maladapted. Such adaptations are termed vestigial. Many organisms have vestigial organs, which are the remnants of fully functional structures ...
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]
Such is the case in whales, which have small vestigial bones that appear to be remnants of the leg bones of their ancestors which walked on land. [53] Humans also have vestigial structures, including the ear muscles, the wisdom teeth, the appendix, the tail bone, body hair (including goose bumps), and the semilunar fold in the corner of the eye ...
It has been suggested that some behaviours might be homologous, based either on sharing across related taxa or on common origins of the behaviour in an individual's development; however, the notion of homologous behavior remains controversial, [44] largely because behavior is more prone to multiple realizability than other biological traits.