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Steven Pinker -- How the Mind Works - Hampshire High Italian ...

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458 | HOW THE MIND WORKSIncest repugnance might be weaker, making him more likely to cross <strong>the</strong>line. It is a special case of <strong>the</strong> lower costs of reproduction for males and<strong>the</strong>ir less discriminating sexual desire, to which we will return.A fa<strong>the</strong>r, moreover, can never be certain that a daughter is his, so <strong>the</strong>genetic cost to him could be zero. That could weaken <strong>the</strong> suppression ofdesire even fur<strong>the</strong>r compared to her bro<strong>the</strong>r, who is certain to be relatedto his sister because <strong>the</strong>y share a mo<strong>the</strong>r. For stepfa<strong>the</strong>rs and stepbro<strong>the</strong>rs,<strong>the</strong>re is no genetic cost at all. It is no surprise, <strong>the</strong>n, that betweenhalf and three-quarters of all reported incest cases are between stepfa<strong>the</strong>rsand stepdaughters, most of <strong>the</strong>m initiated by <strong>the</strong> stepfa<strong>the</strong>r. Mostof <strong>the</strong> rest are between fa<strong>the</strong>rs and daughters, and virtually all arecoerced by <strong>the</strong> fa<strong>the</strong>r. Some are between girls and o<strong>the</strong>r older male relatives,also mostly coerced. A mo<strong>the</strong>r gets no genetic benefit from a matingbetween her husband and her daughter (compared with a matingbetween her daughter and a son-in-law), but suffers <strong>the</strong> cost of defectivegrandchildren, so her interests are aligned with her daughter's and sheshould be a force opposing incest. Incestuous exploitation of girls mightbe even more common if <strong>the</strong>ir mo<strong>the</strong>rs were not around. These battlesare driven by strong emotions, but <strong>the</strong> emotions are not an alternative to<strong>the</strong> genetic analysis; <strong>the</strong> analysis explains why <strong>the</strong>y exist. And of course,in science as in detective work, to try to figure out <strong>the</strong> motive for a crimeis not to excuse <strong>the</strong> crime.People cannot directly sense <strong>the</strong>ir genetic overlap with ano<strong>the</strong>r person;as with <strong>the</strong> rest of perception, <strong>the</strong> brain must combine informationfrom <strong>the</strong> senses with assumptions about <strong>the</strong> world to make an intelligentguess. Chapter 4 showed that when <strong>the</strong> world violates <strong>the</strong> assumptions,we fall prey to an illusion, and that is exactly what happens in <strong>the</strong>perception of kinship. The nineteenth-century anthropologist EdwardWestermarck conjectured that growing up in intimate closeness with aperson in <strong>the</strong> early years is <strong>the</strong> key information <strong>the</strong> brain uses to put <strong>the</strong> personin <strong>the</strong> category "sibling." Similarly, when an adult raises a child <strong>the</strong>adult should perceive <strong>the</strong> child as "son" or "daughter" and <strong>the</strong> childshould perceive <strong>the</strong> adult as "mo<strong>the</strong>r" or "fa<strong>the</strong>r." The classifications <strong>the</strong>nnegate sexual desire.These algorithms presuppose a world in which children who areraised toge<strong>the</strong>r are biological siblings and vice versa. That is certainlytrue of foraging peoples. A mo<strong>the</strong>r's children grow up with her and usuallywith <strong>the</strong>ir fa<strong>the</strong>r, too. When <strong>the</strong> assumption is false, people shouldbe <strong>the</strong> victim of a kinship illusion. If <strong>the</strong>y grow up with a person who is

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