The sciences of evolutionary psychologyhuman behavioural ecologyand sociobiology study the influence of sexual selection in humans. Darwin's ideas on sexual selection were met with scepticism by his contemporaries and not considered of great importance in the early 20th century, until in the s biologists decided to include sexual selection as a mode of natural selection.
Mutual attraction between the sexes is an important factor in reproduction. The males and females of many animal species are similar in size and shape except for the sexual organs and secondary sexual characteristics such as the breasts of female mammals. There are,… Mutual attraction between the sexes is an important factor in reproduction.
There are, however, species in which the sexes exhibit striking dimorphism or physical difference.
Particularly in birds and mammals, the males are often larger and stronger, more brightly coloured, or endowed with conspicuous ornamentation. These traits, however, make animals more visible to predators—the long plumage of male peacocks Pavo cristatus and birds of paradise Paradisaea and the enormous antlers of aged male deer Odocoileus are cumbersome loads in the best of cases.
Darwin knew that natural selection could not be expected to favour the evolution of disadvantageous traits, and he was able to offer a solution to this problem. Other things being equal, organisms more proficient in securing mates have higher fitness.
There are two general circumstances leading to sexual selection. One is the preference shown by one sex often the females for individuals of the other sex that exhibit certain traits. The other is increased strength usually among the males that yields greater success in securing mates.
The presence of a particular trait among the members of one sex can make them somehow more attractive to the opposite sex.
When, for example, Drosophila flies, some with yellow bodies as a result of spontaneous mutation and others with the normal yellowish gray pigmentation, are placed together, normal males are preferred over yellow males by females with either body colour.
Sexual selection can also come about because a trait—the antlers of a stag, for example—increases prowess in competition with members of the same sex.
Stags, rams, and bulls use antlers or horns in contests of strength; a winning male usually secures more female mates. Therefore, sexual selection may lead to increased size and aggressiveness in males. Male baboons Papio are more than twice as large as females, and the behaviour of the docile females contrasts with that of the aggressive males.
A similar dimorphism occurs in the northern sea lionEumetopias jubata, where males weigh about 1, kg 2, poundsabout three times as much as females.
The males fight fiercely in their competition for females; large, battle-scarred males occupy their own rocky islets, each holding a harem of as many as 20 females. Among many mammals that live in packs, troops, or herds—such as wolveshorsesand buffaloes—there usually is a hierarchy of dominance based on age and strength, with males that rank high in the hierarchy doing most of the mating.Discuss the relationship between sexual selection and human reproductive behaviour.
(8 + 16 marks) Here you should focus on sexual selection and the evolutionary origins of mate choice. Sexual selection and the role of parasites. Author links open overlay panel Andrew F. Read. Show more. Contrary to most theories of sexual selection through female choice 2, and discuss the difficulties involved in gathering and interpreting the evidence still required.
This meeting will bring biologists and palaeontologists together to discuss sexual selection’s role in macroevolution, how to detect it in extinct animals and how to measure its influence on the history of life across geological time. Speciation by sexual selection - the role of ecological effects on sexual communication.
Sexual selection may have played a role, for one, with males preferring paler skin in northern latitudes, the researchers surmised.
“One of the hypotheses is that men seem to prefer women with a light skin color, which can be regarded as a sign of youth and fertility,” Juzeniene told LiveScience. That second type of sexual selection, in which one sex chooses among potential mates, appears to be the most common type among birds.
As evidence that such selection is widespread, consider the reversal of normal sexual differences in the ornamentation of some polyandrous birds. Sexual Selection Sexual selection is the process whereby individuals advertise both their own requirements in a mate and their own attractive characteristics as a mate Selection involves attracting the mate with the greatest fitness whilst at the same time maximising the chances of .