Heredity and Hormones
June 26th, 2008
Heredity and Hormones
1. I need to compare and contrast the influence of heredity and hormones on human behavior.
Interestingly, there is a renewed interest in the biological determinants of human behavior. The nature (heredity) theory of human behavior argues that people behave as they do according to genetic predispositions (inherited from family gene pool) or even "animal instincts."Â Â Conversely, the purely biological view is that our â€œhormonesâ€ in the brain determine behavior.Â Â
While it is clear that we inherit â€˜physicalâ€™ ...view middle of the document...
Research on intelligences has found that parents with high/low IQs (intelligence) have children with similar IQ levels.
Other abilities, like singing, playing an instruments, dancing (behaviors), to name a few, also tend to run in the family, and are therefore considered inherited.
Twin studies are used to determine the types of behaviors that are inherited, especially when identical twins have been reared apart (see http://www.heretical.com/miscella/rushton1.html.)
Separating the relative contributions of nature (heredity) versus nurture (environment) to human behavior have always been of compelling interest to biologists. American eugenicists, influenced by August Weismann's germ plasm theory, favored the interpretation that behavioral traits are largely determined by genes â€” which are aloof from environmental influence. French eugenicists, under the lingering influence of Lamark, still favored the notion that environment could modify heredity â€” and thus behavior.
Although the idea of using twins to approach the issue of nature/nurture in humans first occurred to Francis Galton, he did little work on the problem himself. However, he stimulated others to make use of twin studies, which ultimately provided evidence for the downfall of eugenics.
In the 1920s, Herman Muller evaluated a pair of identical twins who had been raised apart from one another. Although they both had high intelligence test scores, they had been raised in unexceptional middle class families in two different Midwestern states. Muller concluded that it would take "an army" of psychologists and geneticists to separate the genetic and environmental components in such twin pairs.
Work in the 1930s by Horatio Newman, Frank Freeman, and Karl Holzinger showed that identical twins raised apart had nearly 100% concordance (agreement) on physical traits â€” such as appearance, longevity, blood groups â€” but showed variable concordance on behavioral and personality traits. Notably, twins raised separately had a 15-point difference in IQ â€” strongly suggesting that intelligence is influenced by upbringing. All this strongly indicated that the eugenicists' simplistic analyses could not hope to account...