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Unformatted text preview: Chapter 4 10/03/2008 12:39:00 Q: the ramifications of having 2 genders is that every other person you meet is someone you cant reproduce with- why is there gender at all? (1) Tragedy of the commons The lack of a single ownership of a piece of land etc. but the rewards are singular if people get greedy. One person will get rich while the group get poorer Ex. Grazing a piece of land or over-fishing the ocean If one person has all sons it would be good for them, but if everyone does it then the group fails Genes can get greedyex. Cancer cells kill other cells 1 st part of chapter Genes can act selfishly just as the individual doesexplains why males and females are different Genes are chromosomes determine gender Gene of Y chromosomes that makes males maleSRY Humans all start life as females If the right genetic switches are not turned of at the right time, people will revert back to the default sex females Ex. Jaime Lee Curtis chromosomally a male but her body didnt respond to testosterone correctly so she looks female Boys vs. Girls at birth should be 50-50 (2) Other ways to determine gender (in animals) 1. Chose the gender appropriate for sexual opportunities If surrounded by males, can become females Change from female to male when they reach a certain size For polygamists, if small be female, if large be male 2. Environment Chooses Ex. Gender is determined by the temperature at which the egg is incubated 3. Mother chooses sex of each child Fertilized eggs become female, unfertilized eggs become male: in bees and wasps, by controlling sperm she controls sexsex allocation Called haplodiploidy: females have 2 sets of genes but males only have one. (3) Robert Trivers Americas youngest prodigyTrivers Willard Noticed that Americans presidents, British Royalty, and other well off American settlers had more males than females (about 60-40) Race to have the most grandchildren Reproductive asymmetry: females (about 20 kids per lifetime), males (thousands-10 thousands kids/ lifetime) Women keep men from reaching their reproductive potential Women dont want to waste their reproductive potential on men they dont knowexplains why men are more out to seek sex without strings attached Especially in polygamous societies, parents in good condition were likely to have male biased litters and vice versa (4) Meg Syminton Spider Monkeys In monkeys, the rank of mother effects the birth ratio High ranking females should have the sex that stays with the troop, be it male or female...
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