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Evolution and the mechanisms of transmission.

The essential concepts in Darwin’s theory of evolution are based on trait diversity between individuals within the species studied. For many species the evolutionary strategy to survive is to have a large number of offspring as many individuals die in infancy. When a heritable trait increases the possibility of survival and reproductive success the frequency of that trait become magnified in succeeding generations. In evolutionary theory some traits produce a higher level of reproductive fitness. Over the eons of time in our Earth’s history evolution has led to systematic genetic changes in the population described by Darwin as natural selection. The natural selection of reproductive fitness is produced by the interaction of individual and cultural groups with the physical and social environments. Most of us are familiar with evolution on a first hand basis having seen the effects of breeding programs by farmers that accelerate natural selection by selecting animals for breeding that have desirable characteristics.

Although mutations play a role in the evolution of lower species, the longer life cycles of humans preserve a stronger change effect from cultural factors including migration and choice in mating. Migration and isolation from other geographical groups can produce variations due to random occurrences also called genetic drift. Random fluctuations are of little importance in large populations, but may produce measurable long term effects in small populations. Therefore the initial gene pool of an immigrant group may have long term effects on the phenotypes of subsequent generations. The phenotypes of racial differences are such long lasting effects found initially in small genetic immigrant populations. Nevertheless these phenotypical gene pools for the most part refer to unimportant visible traits like skin tone. Non-random choice for sexual partners is also a factor in human evolution as these choices are governed in most societies by social rules. Daughters of the rich marry sons of the rich and in that social rule for reproductive fitness we can observe a certain amount of inbreeding and control over social resources. In some societies marriage is encouraged between close relatives reducing genetic variability. In modern societies probably the most prominent selection device is education. Since education is also related to intelligence, selection may play a role in the variability of that trait.


Date: 2015-01-11; view: 864


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