https://en.wikipedia.org/wiki/Inbreeding
Inbreeding is reproduction from the mating of pairs who are closely related genetically.[1] Inbreeding results in homozygosity, which can increase the chances of offspring being affected by recessive or deleterious traits.[2] This generally leads to a decreased fitness of a population,[3][4] which is called inbreeding depression. An individual who results from inbreeding is referred to as inbred. The avoidance of expression of deleterious recessive alleles caused by inbreeding is thought to be the main selective force maintaining the outcrossing aspect of sexual reproduction.[5][6] (See also Inbreeding depression.)
...All in the Family.
The explanation for inbreeding depression lies in the evolutionary history of the population. Over time, natural selection weeds deleterious alleles out of a population—when the dominant deleterious alleles are expressed, they lower the carrier’s fitness, and fewer copies wind up in the next generation. But recessive deleterious alleles are “hidden” from natural selection by their dominant non-deleterious counterparts. An individual carrying a single recessive deleterious allele will be healthy and can easily pass the deleterious allele into the next generation.
When the population is large, this is generally not a problem—the population may carry many recessive deleterious alleles, but they are rarely expressed. However, when the population becomes small, close relatives end up mating with one another, and those relatives likely carry the same recessive deleterious alleles. When the relatives mate, the offspring may inherit two copies of the same recessive deleterious allele and suffer the consequences of expressing the deleterious allele
http://evolution.berkeley.edu/evosite/relevance/IIIA1Inbreeding.shtml
University of Virginia professor of psychology, Jonathan Haidt summarizes the current state of psychological research on the conservative mind:
conservatism is a partially heritable personality trait that predisposes some people to be cognitively inflexible, fond of hierarchy, and inordinately afraid of uncertainty, change, and death. People vote Republican because Republicans offer "moral clarity"—a simple vision of good and evil that activates deep seated fears in much of the electorate. Democrats, in contrast, appeal to reason with their long-winded explorations of policy options for a complex world.
In this view, the moral system favored by conservatives appeals greatly to people who are fearful of change and prone to authoritarian thinking styles.
So how deep do these personality traits go? A team of scientists from UCLA and NYU published the results of an experiment in Nature Neuroscience showing that self-identified conservative and liberal students displayed different cognitive behavior patterns in computer simulations. Thus, liberal students proved far more sensitive to cues for switching response patterns, whereas conservative students tended to filter out the cues as distracting information. They conclude that the cognitive styles of self-reported conservatives were more "structured and persistent," whereas those of liberals showed "greater tolerance for conflict and ambiguity," suggesting they were "more open to new experiences." Similarly, a 2003 review of psychological research on self-identified conservatives across a number of countries concludes that individuals tend to adopt conservative ideologies "to reduce fear, anxiety, and uncertainty; to avoid change, disruption, and ambiguity; and to explain, order, and justify inequality among groups and individuals." In short, people who gravitate toward conservative ideologies tend to be psychologically motivated by the need to manage uncertainty and fear.
But why does conservatism tend to run in families? Are some families more fearful than others? If so, is this innate or learned? And which came first--conservatism or the social cognitive need for conservatism?
A fascinating study published in the American Political Science Review in 2005 suggests that, to some extent, conservative and liberal orientations are heritable. The study reported the results of twin studies showing that monozygotic twins (those who share 100 percent of their genetic material) were far more likely to have the same attitudes on a range of political issues than dizygotic twins (those who share 50 percent of their genetic material), controlling for having been raised together or separately and a whole host of other factors.
http://erinjenne.blogspot.com/2010/08/explaining-conservative-mind-are-you.html
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