CHAPTER 12.docx

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26 Apr 2012
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CHAPTER 12
EVOLUTION OF HUMANS
Evolutionary psychology: attempts to apply the principles of adaptation and selection to human
behavior
Evolutionary Theory
Ideas by others, but put together by Darwin and Wallace;
1) Classification of organisms based on structure by Carolus Linnaeus
2) Charles Lyell and William Smith observed that the earth was far older than was previously
thought through the studies of fossils and geological processes
3) Thomas Malthus observed the food supplies affect populations (survival of the fittest)
Historical Theory of Evolution
Historical theory of evolution can be summed up by three terms; variation, inheritance, and
differential reproduction
All individuals vary, which results in differences in morphology, which can be passed from one
generation to the next, and these individual differences in morphology can result in variations in
success in the environment in terms of survival and reproduction
Darwin suggested that the mechanism underlying these changes was natural selection: requires
that all individuals are unique and that characteristics that give an animal a reproductive
advantage will result in the magnification of these traits in the population
Adaptation: when a trait results in a reproductive advantage and is selected for
For a trait to be an adaptation it must be inherited from one generation to the next
Sexual selection: it is competition among individuals for survival to reproduce that determines
which genes remain in the gene pool and which genes disappear from the face of the planet
Two types of sexual reproduction:
1) Intersexual selection: one sex chooses a mate from among members of the other sex on the
basis of specific traits
2) Intrasexual selection: members of the same sex compete for partners of the opposite sex
The original theory of evolution is referred to as the historical theory of evolution because of
the changes to the theory that have occurred since its inception since when Darwin and Wallace
formulated the theory of natural selection, they did not know why variation occurred, or how
traits were passed down
We now know traits are passed down by genes and that the original source of variation is the
random mutation of these genes
Current theory of evolution is referred to as the Modern Synthetic Theory of Evolution or
modern synthesis
Modern Synthesis
Is based on what is known about genes, DNA, and population biology
Your genotype is invariant during your lifetime, phenotype is the interaction of your genotype
with the environment in which you develop
More than one form of a gene = alleles
Homozygous = both alleles are the same
Heterozygous= two different alleles
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