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Evolutionary Psychology
of Sex and Behavior
(A Very Brief Introduction)
by Benjamin Brumfield
Evolutionary Psychology
• In order to appreciate the study of our behavior and our
minds – which is the general goal of psychology – I think that it
is important to have a solid understanding of these 3 things:
The underlying structures that give rise to our thoughts and
behaviors (anatomy)
How the systems of the body interact to create, influence and
alter our minds/behaviors (physiology)
And, equally important, why these systems evolved to be the
way they are (through adaptation and natural selection)
Evolutionary Psychology
• So, one of the key points of evolutionary psychology is to
explain human behavior in terms of adaptability over time.
• Just as physiologists study other animals and apply their
research to humans, evolutionary psychologists, with careful
consideration not to anthropomorphize other species’
motivations, also draw comparisons between those other
species’ behaviors and our own (especially among the
Evolutionary Psychology
• Views human behaviors as products of natural selection
Feelings & Expressions
Altruism & Sharing
Having Friends & Enemies
Religious beliefs/rituals?
• Explains (or attempts to) the adaptive significance of our
• Example: The adaptive benefit for a male to have many mates.
This helps explain why the human male may not be an exemplary
model of monogamy today. (For other, similar reasons, it explains
why, under certain circumstances, women might be polygamous
as well.)
Evolutionary Psychology
• Also explains things like:
• Our aggressive/murderous tendencies when we are frustrated or
blocked from achieving an important goal.
• The alarming/surprisingly high rate of infanticide (by step-fathers)
throughout the world.
• Our obesity issues – when would we have learned the benefits of
moderation before modern times?
• Our debt issues –When would we have had resources (such as
money) that wouldn’t lose value/rot if not quickly consumed?
• Does the stage of a woman’s menstrual cycle affect how
attractive she is (as rated by other males and females)?
Study by Geoffrey Miller (2007)
• Counted average hourly tips made by lap dancers employed
by gentlemen’s clubs in Albuquerque, New Mexico.
• Found that strippers made an average of…
• $70 per hour during the fertile phase of their menstrual cycles
• $35 per hour during their periods
• $50 dollars per hour during the rest of the month.
• An interesting note:
the women that were on birth control showed no mid-cycle peak in earnings
and had significantly lower overall income than women not on birth control.
Study by Geoffrey Miller (2007)
1. Average shift was 5.2 hours
2. Menstrual phase (Days 1–5 of the cycle), Fertile phase (Days 9–15 of the cycle), Luteal phase (Days 18–28 of the cycle)
Study by S. Roberts et. al. (2004)
• Had male and female viewers choose which of two images of
the same female was more attractive
•(one was during her fertile phase and one during her luteal phase).
•In each picture, the female wore no cosmetics and displayed a
neutral expression.
•Raters performed this preference test twice: with digitally masked
images (digitally obscuring ears and hair) and with unmasked
images (retaining these cues).
•Replicated studies at University of New Castle, UK and Charles
University in Prague.
Evolutionary Implications
• I think the evolutionary implications are clear:
• It is adaptive for the males of a species that are able to
• Pick up on cues about a female’s fertility
• Act on those cues.