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The Organizational-Activational Hypothesis states that steroid hormones permanently organize the nervous system during early development, which is reflected in adult male or female typical behaviors. [1] In adulthood, the same steroid hormones activate, modulate, and inhibit these behaviors. [2] This idea was revolutionary when first published ...
The Barker Hypothesis, or Thrifty phenotype, forms the basis for much of the research conducted on fetal programming. This hypothesis states that if the fetus is exposed to low nutrition, it will adapt to that particular environment. Nutrients are diverted towards the development of the heart, brain, and other essential organs of the fetus.
The concept of sexual selection was introduced by Charles Darwin as an element of his theory of natural selection. [1] Sexual selection is a biological way one sex chooses a mate for the best reproductive success. Most compete with others of the same sex for the best mate to contribute their genome for future generations.
The hormonal theory of sexuality holds that, just as exposure to certain hormones plays a role in fetal sex differentiation, such exposure also influences the sexual orientation that emerges later in the adult. Differences in brain structure that come about from chemical messengers and genes interacting on developing brain cells are believed to ...
The hypothesis separately proposes that hormonal changes across the cycle cause women, when they are most likely to get pregnant, to be more attracted to traits in potential short-term male sexual partners that indicate high genetic quality, leading to greater reproductive success. [3]
The Trivers–Willard hypothesis has been applied to resource differences among individuals in a society as well as to resource differences among societies.Investigations in humans pose a number of practical and methodological difficulties, [6] but while a 2007 review of previous research found that empirical evidence for the hypothesis was mixed, the author noted that it received greater ...
These examples all culminate in a challenge hypothesis model which focuses on the role of testosterone on aggression in the breeding season. The challenge hypothesis most likely cannot be applied to the non-breeding season since, as mentioned above, there is most likely a mechanism independent of testosterone governing aggression in the non ...
Bateman initially published his review in 1948. [1] He was a botanist, contributing to the literature of sexual selection only once in his lifetime. Bateman initially saw his study on Drosophila to be a test of Charles Darwin's doctrine of sexual selection, [2] which he saw not as flawed, but as incomplete. He felt that if he were to provide a ...