Chapter 9 Primate Life Histories and the Evolution of Intelligence

Chapter 9 Primate Life Histories and the Evolution of Intelligence

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Chapter 9: Primate Life Histories and the Evolution of Intelligence Big Brains and Long Lives - Two features that describe the primate order are large brains and long life spans o Primates rely more heavily on learning to acquire the skills and knowledge that they need to survive and reproduce successfully - Selection for larger brains generated selection for long lives o Animals that live for a long time will derive a greater benefit from the energy they expend on building and maintaining their brains Life History Theory - Life history theory focuses on the evolutionary forces that shape trade-offs between the quantity and quality of offspring and between current and future reproduction - Aging and death result from trade-offs between reproduction at different ages and survivorship o Natural selection cannot do away with aging, even though it is not inevitable because being built better requires more energy, which would reduce our growth rate and early fertility - The trade-off between survival and reproduction is greatly biased against characteristics that prolong life at the expense of early survival or reproduction o Aging is favored by selection because traits that affect fertility at young ages are favored at the expense of traits that increase longevity o Selective pressures are much weaker on traits that affect only the old Ex: there are two alleles, one which kills an individual before they reach adulthood; the other kills the individual at a later age The first one cannot reproduce The second allele will have little effect on the fitness of the individual because they will have already produced a lot of offspring - The trade-off betwe e n current a nd future reproduction a nd betwe e n qu antity a nd quality of g e n er at e s const ellations of interrelat ed traits o Animals that be gin to reproduce e arly h ave s m all body sizes, s m all brains, short g est atio litters, high rates of m ort ality, a nd short life spa ns o The opposite is true for a nim als that reproduc e later in life o Animals that be gin to reproduce e arly divert e n ergy from growth a nd re m ain s m all o All thes e ar e b ec a us e of the fact that there ar e trad e-offs betwe e n current a nd future rep the qu a ntity a nd qu ality of the offspring - The be n efits derived from current a nd future reproduction de p e nd on a variety of ecological influence the prospects for survival o It m akes little s e ns e to divert e n ergy to future reproduction if the prospects for surviving ar e slim Ex: a nim als that ar e often prey - Natural s election not only sh ap e s the relationship b etwe e n life history traits, but it can also of thes e traits in respons e to chang e s in e nvironm e nt al conditions o Animals can h ave a d ec elerat ed life history in m ore favorable e nviron m e nt al conditions The Evolution of Primat e Life Histories - Primat e s fall so m ewh ere along the slow/long e nd of the life history continuu m o However, there is variation within the prim at e order
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This note was uploaded on 04/21/2009 for the course ANTH 200Lg taught by Professor Yamashita during the Fall '07 term at USC.

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Chapter 9 Primate Life Histories and the Evolution of Intelligence

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