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BIO318 Lecture 23 (Dec 2).docx

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University of Toronto Mississauga
Sanja Hinic- Frlog

BIO318 Lecture 23 - Last day o Sexual dimorphism and anatomy (e.g. testis size) in humans indicates a history of sexual selection  Gorilla has monogamous system while chimpanzees are promiscuous o Extra-pair bond copulation rates in western societies – and likely sperm competition – lead to an average 1% of all births (higher in the few traditional societies that have been studied) o (not mentioned last day): - Demographic transition in Gwynne Ancestry o Trend that there’s a decrease in offsprings in later years - The demographic transition o Is it important to study evolutionary psychology o If there’s high condition females, she’ll have high condition offsprings; she’ll want to invest in high condition males so that her offsprings are in exceptionally high condition o Biased towards males and high condition females o In an example, they were supplementary feeding the females and the offsprings and then there’s a biased sex ratio that favours males which is not ideal in that situation for endangered species o Daughters are more valuable than sons because they can provide more offsprings o So they starved them a bit and then there was a female biased ratio o What are going today that will reflect a future change?  Number of offsprings is what we look at for sexual fitness  There are some trend that tall men have more offsprings - Reduced fertility despite increase in wealth o Erosion of common correlation between resources and fertility in pre-transition societies (e.g. association between income and fertility in U.S Women is negative - Hypotheses o Decreased need for offspring replacement o Maladaptation? E.g. “adaptive lag to novel socioecological factors such as contraception” o Breast feeding as a method of contraception - Hypotheses: optimizing family
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