PSYB65 - Chapter 12 - Sep 13, 2010
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Chapter 12 Humans, Human Brains, and Evolution
Module 12.1: Evolution of Humans
Evolutionary psychology – attempts to apply the principles of adaptation and selection to human
-How our environment has affected the development of our species as well as the specific
demands and subsequent adaptations that evolved to deal with these challenges.
-Charles Darwin and Alfred Russel Wallace
The classification of organisms based on structure by Carolus Linnaeus, which he
observed that there were commonalities in structure among related species.
Charles Lyell and William Smith supported the notion that the earth was far older than
was previously thought. When changes occurred, they occurred in a predictable manner
in the strata of the earth
Thomas Malthus observed that food supplies affect populations, similar to the
evolutionary theory (survival of the fittest). He suggested that populations grow
exponentially until they surpass their food supply, which leads to a struggle for existence.
Historical theory of Evolution
-Variation, inheritance and differential reproduction
All individuals vary, which results in differences in morphology. These differences in
morphology can be passed from one generation to the next. These individual differences
in morphology result in variations in success in the environment, in terms of survival
-Natural selection – competition among individuals for survival to reproduce that determines
which genes remain and which genes disappear.
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 population.
Adaptation – when a trait results in a reproductive advantage and is selected for.
(Must be inherited from one generation to the next)
Different environments may result in the selection of different traits
Because the environment is not static and variation never truly goes away, natural
selection must be continually occurring.
-Sexual selection – competition among individuals for reproduction that determine a gene’s
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.
-Traits are passed on by genes and that the original source of variation is the random mutation
of these genes.
-The current version of evolutionary theory (referred to as the modern synthetic theory of
evolution / the modern synthesis.
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