a201-11f-17-MatingSexualSelection

This reduced the males clues about whether or not

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this reduced the males’ clues about whether or not they are the father - it increases the odds that any given male in the group is the father - so it increases the costs to a male of killing infants, since they might be his own - consider humans - human females are unusual in that they have concealed ovulation - they don’t have obvious periods of estrus (being “in heat”) - they are generally receptive to sex throughout their cycle - this makes it hard for males to know who the father of the female’s offspring is - it also makes it even more important to a male’s reproductive success that he keeps an eye on the female, to keep other males away - so concealed ovulation benefits the female’s r.s. - reduces likelihood of a male committing infanticide - since he can’t know that the infant is not his own - increases the likelihood that the male will stay nearby most of the time, not just occasionally when the female is in estrus - so he can mate with her frequently, since he can’t tell when the female can actually conceive - and to keep other males away all the time, since he can’t tell when it is safe to leave her alone - in hanging around, he may improve the female’s access to food patches - he may defend the infant from other males - female choice may also play a role in multi-male, multi-female groups - in some species, females prefer dominant males - apparently because dominant males have better access to food, and males allow their own offspring to feed near them - so the offspring of a female that mates with a dominant male have better access to food, grow faster, etc. - in others, such as some macaques, some females prefer unknown, lower-ranking males to dominant ones - since the dominance hierarchies are long-lasting, this may be beneficial to a female's reproductive success because it adds different genes to her offspring -- increases variability - The overall point: Sexual selection can explain how and why a lot of physical traits and complex social behaviors evolved - in many cases, sexual selection apparently favored individuals who were most able to
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Intro to Biological Anthro F 2011 / Owen: Sexual selection p. 10 - learn and remember things about specific other individuals - use that knowledge to make complex judgments about dominance, mating opportunities, parenting, coalitions, etc. - generally more complex thinking than is needed to get food or avoid predators - that is, sexual selection probably played a major role in the evolution of big brains and complex behavior - in primates in general - and later in the lineage that led to humans - Points for specifically human evolution: Our ancestors probably evolved in monogamous (pair- bonded) social groups - based on our minimal sexual dimorphism - and testes size relative to body size in the intermediate range - not as big as in multi-male, multi-female groups - but not as small as in single-male, multi-female groups - so male-male competition in the usual sense was probably not a big factor in the evolution that led to humans -
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