A Brief View of Evolution and Behavior Genetics Myths about Evolution not just a theory but the framework for all of biology this framework does not prove or disprove a deity humans are not more evolved than other species humans did not evolve from apes but rather apes and humans have a common ancestor evolutionary adaptations build on what exists so it often is not optimal Evolution of the brain Neurons originated early in phyla Cnidaria jellyfish sea anemones as nerve nets Some invertebrates animals without a backbone have concentrations of neurons that are considered brains Vertebrates have the same basic brain parts spinal cord hindbrain midbrain and forebrain Between species the size of the brain and size of the body are approximately proportional Within a species this relationship does not always hold Behavior Genetics All behavior is influenced by genetics Genetics and the environment make up the organism the Phenotype A statistic Heritability H2 proportion of the population variance accounted for by genetic variance Zero means nothing in phenotypic variation is accounted for by genetic variation 1 means all of the variability in the population is accounted for by genetic variability The example to the right is H2 1 Misunderstandings about Heritability High heritability does not mean low environmental influence The Heritability statistic can change in different environments It does not apply to individuals If H2 for height is 0 8 it does not mean a 5 foot individual has 4 feet from genetics and 1 foot from the environment H2 does not say anything about how genes or the environment works on the phenotype The correlation between the IQ of the children and their adoptive parents is low but as a group they had a large environmental influence
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