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Sexual selection creates colourful differences between sexes in Goldie's bird-of-paradise.Male above; female below. Painting by John Gerrard Keulemans.. Sexual selection is a mechanism of evolution in which members of one sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual ...
In that view, many human artifacts could be considered subject to sexual selection as part of the extended phenotype, for instance clothing that enhances sexually selected traits. [2] During human evolution, on at least two occasions, hominid brain size increased rapidly over a short period of time followed by a period of stasis.
One example of a sexually selected trait with direct benefits is the bright plumage of the northern cardinal, a common backyard bird in the eastern United States. Male northern cardinals have conspicuous red feathers, while the females have a more cryptic coloration.
For example, male traits such as the presence of beards, overall lower voice pitch, and average greater height are thought to be sexually selected traits as they confer benefits to either the women selecting for them, or to their offspring. Experimentally, women have reported a preference for men with beards and lower voices. [2] [3] [4]
This is the genic capture hypothesis, which describes how a significant amount of the genome is involved in shaping the traits that are sexually selected. [4] There are two criteria in the genic capture hypothesis: the first is that sexually selected traits are dependent upon condition and the second is that general condition is attributable to ...
The more physically attractive a man is, the higher his fitness, and the "better" his genes will be. Women are attracted to masculine traits greater in sexual dimorphism (e.g. strong jawline, a more muscular body, a taller height). Indeed, men who are more masculine tend to have a higher number of sexual partners. [3]
Another potential resolution to the lek paradox is Rowe and Houle's theory that sexually selected traits depend on physical condition, which might in turn, summarize many genetic loci. [52] This is the genic capture hypothesis, which describes how a significant amount of the genome is involved in shaping the traits that are sexually selected. [51]
Sexually selected traits often evolve to become more pronounced in competitive breeding situations until the trait begins to limit the individual's fitness. Conflicts between an individual fitness and signaling adaptations ensure that sexually selected ornaments such as plumage coloration and courtship behavior are "honest" traits.