On Human Nature

I will now try to answer the question of how much genetic

I will now try to answer the question of how much genetic variation there is in our own social behavior This is an important and nuanced question The fact that human behavior is still based on physiology and that mammals are most closely related to it suggests that human behavior has until recently been subject to genetic evolution If so The influence of genetic variation on behavior may even have persisted into the age of civilization but that is not to say that such variation exists today There are two possibilities that can be envisaged for this the first being that by the time humanity enters its present state its genetic variability has been exhausted Humans have one set of genes that influence social behavior but only one Many social scientists clearly agree that this group of genes has survived the long and arduous journey of prehistory Within the political ideology that refers to these issues many left-wing intellectuals share the same attitude They admit that human beings have undergone evolution but this evolution stopped when they became a unified linguistic and cultural species As far back as history humans have been the fine clay in the hands of the environment left to be moulded so now only the movement of culture in and out is possible

The second possibility is that there is at least some genetic variation in humans Humans may have stopped evolving just as the old biological model of natural selection has relaxed but they still have the ability to evolve genetically and culturally The reader is cautioned that any possibility that human variation is determined solely by culture or that it is determined by both culture and heredity is consistent with a more general sociobiological view of human nature namely that the most prominent features of brass tube fitting human behavior are acquired through natural selection And today the whole human race is still bound by some special genes Having stated the above possibilities in a textbook way I must add that there is ample evidence that a large part of the variation in human behavior is based on genetic differences between individuals The existence of genetic variations that affect human behavior is undeniable Among the various changes in the chemical composition of genes or in the structure and arrangement of chromosomes more than 30 changes have been identified that affect human behavior ranging from neurological disorders to intellectual impairment One of the most controversial but valuable examples is the xyy male The X and y chromosomes determine a person's sex; the XX combine to produce a female and the XY combine to produce a male Occasionally about 0 One percent of people get an extra Y chromosome and these xyy people are all male and grow up to be tall mostly over 6 feet They often end up in jail or hospital for criminal mental illness

At first it was thought that the extra chromosome induced more aggressive behavior resulting in a class of hereditary criminals However after studying a large number of Danish data statistically Herman Witkin 38 tube fitting a psychologist at Princeton University and his colleagues developed a more generous interpretation They found that The xyys are not more aggressive than the rest of the population nor do they show any particular pattern of behaviour that differentiates them from other Danes The only anomaly is their lower average intelligence The simplest explanation is that the xyys have a higher rate of imprisonment simply because they are less alert and easier to detect It should be noted though that This study does not exclude the possibility of inheritance of more specific qualities that may lead to criminal personality In fact several mutations have been shown to alter behavioral traits Turner syndrome occurs when only one of the two X chromosomes is transmitted Not only is general mental retardation affected but the ability to recall shapes and to distinguish left from right in figures is greatly impaired The Lessie-Nehan syndrome caused by a single recessive gene causes not only mental retardation but also compulsive tendencies to tear the body apart to the point of self-mutilation People suffering from these and other genetic diseases are as severely retarded as those suffering from severe mental retardation

Genetic analysis is the best form of analysis that can be used to study these conditions Whenever there is an abnormality in addition to drug treatment we can closely examine it try to identify the part of the brain that has changed and use hormones and other chemicals to mediate the change Without physical contact with the brain that is we can understand the whole machine by the malfunctioning of its parts We don't want to fall into the trap of sentimentalism as a cruel process because doing so is the surest way to find a cure for these abnormal conditions Most of the strong variations that are as easy to analyze as Turner anomalies and Lessie-Nahan anomalies will also cause defects and diseases

This is true for animals plants and people and it is entirely predictable To understand why this is we can compare the genetic mechanism with the delicate structure of the watch If the watch changes when it is shaken and hit at random Just as specific chemical properties are arbitrarily changed by variability the accuracy of a table is likely to be compromised rather than improved However this powerful set of examples does not answer the question of the evolution of genetic variation and "normal" social behavior Human traits as complex as human behavior are usually influenced by many genes each of which plays only a small role These "polygenes" can not usually be identified by detecting and tracing the changes that cause them but can only be estimated by indirect statistical methods In human behavioral genetics The most widely used method compares identical twins and dizygotic twins Identical twins develop from a fertilized egg in the womb The two cells produced by the first division of an egg are not stuck together to produce a fetus but the two cells are separated to produce two fetuses Because twins are produced from the same cell the same nucleus and the same set of chromosomes They are genetically identical Dizygotic twins on the other hand are eggs that happen to enter the reproductive tract and combine with different sperm at the same time The resulting fetuses are genetically similar to siblings born in different years chinaroke.com


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