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Lecture 13

BIOL 2400 Lecture 13: Human Evolution and Natural Selection Class Notes

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BIOL 2400
Teresa Crease

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BIOL*2400 Dr. Crease Winter 2017 Human Evolution Lecture 13 Hominin brains were same size as chimp brains for first few million years o Brain size increase 2 MYA until 100 KYA Modern human brains are nearly 3 times as large as early hominins o Hypothesis to explain increase is ultrasociality Juvenile humans will develop social skills earlier than juvenile great apes In primates, brain size positively correlated with social group size No difference is expected in development of physical skills Results of studies support hypothesis that humans have more highly developed social intelligence o Features that differentiate human brains from great apes may have evolved through changes in patterns of gene regulation and gene expression FOXP2 gene (forkhead box protein P2) o Protein encoded by FOXP2 required for proper development of speech and language Protein is a transcription factor that regulates expression of many other genes o Present in other vertebrates and is involved in neural development (brain development) o Has been under recent positive selection in modern human lineage o Differs in chimps and gorillas by 2 amino acids Natural Selection Does it still operate in humans? o Evidence for directional selection in life history, morphological and physiological traits in modern humans over past 3 centuries Humans have more control over environment, but by changing it, creation of new selection pressures occurs Natural selection operates despite medical intervention in industrialized countries o Despite medical advances, diseases are environmental stressors that can exert selective pressure on humans FY*O allele confers resistance to malaria HIV exerts selective pressure on human populations Does medical intervention increase frequency of detrimental traits in humans? o Myopia = nearsightedness Glassescontacts can correct myopia = not detrimental Disease Despite operation of NS and medical intervention, humans are susceptible to disease and injury
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