Behavior Genetics Essay Research Paper Human Behavior

Behavior Genetics Essay, Research Paper Human Behavior Genetics To illustrate a point concerning the inheritance of gestures, Charles Darwin quoted an interesting case that had been brought to his attention by Galton. A gentleman of considerable position was found by his wife to have the curious trick, when he lay fast asleep on his back in bed, of raising his right arm slowly in front of his face, up to his forehead, and then dropping it with a jerk so that the wrist fell heavily on the bridge of this nose. The trick did not occur every night but occasionally. Many years after his death, his son married a lady who had never heard of the family incident. She, however, observed precisely the same peculiarity in her husband…One of his children, a girl, has inherited the same

trick.? (Darwin, 1872: 33-34) Probably everyone could cite some examples, perhaps not as quaint as Galton?s, in which some peculiarity of gait, quality of temper, degree of talent, or other trait is characteristic of a family, and such phrases as ?a chip off the old block?, ?like father, like son,? and ?it runs in the family? give ample evidence of the general acceptance of the idea that behavioral traits may be inherited, as are physical ones. Discussion What Is Behavioral Genetics: Behavioral genetics is simply the intersection between genetics and the behavioral sciences. Behavioral geneticists are currently applying the various techniques of genetic analysis to various behavioral characters in order to learn more about them. The characters under study are diverse, varying in

subject from homosexuality, IQ, and even hostility. Homosexuality: Many theories have been presented to explain homosexuality behavior in humans. Two of these such theories are E. Slater?s Birth order and maternal age of homosexuals theory and hormonal differences. Birth Order and Maternal Age of Homosexuals: E. Slater?s studies in homosexuality led him to the finding that male homosexuals tend to be born late in sibling order. He found an increase in mean birth order, and increase in maternal age at birth, and a variance of maternal age as great as that of patients with Down?s syndrome (mongolism) This increase approached the figure obtained in the small series of Turner?s and Klinefelter?s cases in the literature and differed widely from that of the general population. Slater

regarded these findings as supporting a hypotheses of heterogeneity in the etiology of homosexuality in the male and as suggesting that a chromosomal anomaly such as might be associated with late maternal age may play a part in causation in some instances. To be sure, this information was reinvestigated and found that a shift in paternal age was primary; this finding would rule out a chromosomal theory and suggest a genetically predisposition to sexual deviance manifesting in the fathers (Kaplan, 1976: 301-304). Hormonal Differences: Another theory on the subject of homosexuality deals with hormonal differences in adult homosexuals. Low urinary testosterone levels have been noted in male homosexuals and, likewise, female homosexuals have been reported as excreting low levels of

estrogen. IQ and Behavioral Genetics: Human intelligence can be usefully construed as a single trait which is largely under genetic control. The influence of different genetic and environmental factors have been estimated, but only crudely. A study of foster children by Skodak and Skeels showed that both the rate of increasing resemblance to true parents and the final level achieved is the same regardless of whether children are raised by their true parents or not. This is extremely strong evidence in support of genetic control of intelligence. However, that same study also revealed evidence that the children?s? IQ levels were in fact, higher on average than the mothers. These differences can be attributed to adoption (Barker,1995: 74-79). There is interesting evidence that