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L24 – Human Evolution

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Western University
Biology 1001A
Tom Haffie

L24 – Human Evolution Are we still evolving and if SO, in which direction are we evolving? Student Answers: - survivorship is much higher, less struggle for existence, perhaps natural selection not necessary - historically we would have adapted to fit our environment, now we adapt our environment to suit ourselves - we adapt ourselves? Gene therapy, certain medical techniques, artificial selection - yes but not in the same direction, as our environment is so different our directional selection is favouring very different traits than would have been historically favoured. Selection is NOT the only mechanism resulting in evolution - Approaching Hardy-Weinberg equilibrium for some traits? - Genetic drift is NOT as prevalent as it was in the past - Genetic structure is changing , exchanging of alleles is becoming a very common thing - There are no “New” populations that could suddenly introduce radical alleles Are we?? - “Believing as I do that man in the distant future will be a far more perfect creature than he now is..” Darwin thought that not only are humans still evolving but still due to some form of selection - “There’s no biological change in humans in 40K years, everything we call culture and civilization we’ve built with the same body and brain” - We have such strong control over our environment - Why might we stop? - weaker natural selection due to medical advances - babies born now have extremely good chance of survival, wasn’t always true - individuals with bad medical conditions can now not only survive but can successfully reproduce - advances in modern medicine have liberated us from natural selection - ^^ NOT TRUE EVERYWHERE, Many kids die before the ager of five in some areas of the world (>10million) - Weaker sexual selection due to monogamy - Sexual selection is an important evolutionary force - Decreasing acceptance of highly polygynous societies - There is still competition among quality of males, variation in reproductive success associated with this - Rockstars have very high reproductive success - Sperm donors, reproductive assistance/ raises possibility that some individuals contribute disproportionately to the next generation - Many opportunities for sexual selection to continue to act - Fewer mutations due to decreasing reproduction by old men - Mutation is ultimate source of genetic variation - Without mutation evolution would grind to a halt as no genetic variation would be introduced - Old men are a mutagenic force - 29 yom: 300 cell divisions - 50 yom: >1000 cell divisions - old men contribute more mutations to gene pool - average pater
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