Download Running head: FEMALE ORGASM FEMALE ORGASM Summary of

Running head: FEMALE ORGASM
Summary of “The Evolution of Female Orgasm: Adaptation or Byproduct?”
Julie Hernandez, Samantha Kargari, Hannah Stuber, Nora Mansfield
Loyola Marymount University
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Puts and Dawood (2006) provide evidence from several studies that the female
orgasm functions more as an adaptation than a byproduct. They negate Elisabeth Lloyd’s
(2005) article and her assertions of the female orgasm as a byproduct of the functional
male orgasm. Lloyd uses West-Eberhard’s definition of an adaptation as a character that
has some evidence of evolving for more effective performance and underwent change
due to increased fitness. Puts and Dawood (2006) argue that selective pressures do not
have to be presently operative for a trait to exist as an adaptation. Many human mating
adaptations have been short-circuited by recent changes in the human mating
environment, such as birth control, media, and medicine. The authors also assert that
Lloyd promotes an unclear identification of byproducts, with premises that include the
shared development of the adaptation and its byproduct. This is an insufficient
explanation of a byproduct, as the plumage of peahens and peacocks are developmentally
related, but both adaptations (Puts & Dawood, 2006). Lloyd also states that byproducts
must have the absence of an efficient design and may appear reduced or seen as remnants
of its corresponding adaptation in the opposite sex. Selection shapes sex-specific
adaptations by modifying structures shared by both sexes, as exhibited in male and
female orgasms (Puts & Dawood, 2006). Female orgasms are not reduced compared to
the male orgasm and are often very intense and exist in multiples. This evidence negates
Lloyd’s claim that the female orgasm fits the definition of a byproduct.
The female orgasm can be viewed as an adaptation from the findings of several
studies cited by Puts and Dawood (2006). Evidence for the female orgasm is less direct
because past selection cannot be measured. The female orgasm must be designed for
some fitness-increasing function, and the sperm-competition hypothesis offers
explanation as to why the female orgasm exists. Multiple males mate with the same
female, and the winner’s sperm fertilizes the female’s egg. The human population favors
large testes and rapid evolution of proteins in ejaculate production. These traits are
greater in humans than gorillas, a species in which sperm competition is low. The spermcompetition hypothesis maintains that the female orgasm promotes conception from
males of high genetic quality (Baker & Bellis, 1993; Smith, 1984; Thornhill et al., 1995).
Several studies cited by Puts and Dawood (2006) provide evidence that the female
orgasm is a copulatory mate choice mechanism. There are lower orgasm rates in females
because the cost of a bad mating is much larger for the female. The female orgasm
promotes earlier entry of sperm into the cervix (Levin, 2002). The patterns of brain
activation and hormone release allow for the movement of sperm into the uterus (Wildt et
al., 1998). The female orgasm was found to release oxytocin into the bloodstream, which
then induces uterine contractions and transportation of the semen (Knaus, 1950; Wildt et
al., 1998). The female orgasm was less elicited during heterosexual intercourse than
masturbation because of the discriminatory nature of the female orgasm during
copulation. The orgasmic vaginal contractions may excite male ejaculation (Meston et al.,
2004). Also, the associated pleasurable sensations of an orgasm may lead to more
copulation with that same male. The female orgasm must be choosy in order to aid in
finding and keeping the most genetically suitable mate for the female.
There is some evidence that men with higher genetic fitness elicit more orgasms
from females (Puts & Dawood, 2006). There is a positive correlation between a male
partner’s bilateral symmetry and female orgasm rates from copulation (Thornhill et al.,
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1995). Only female higher sperm-retention orgasms were significantly associated with
male symmetry (Thornhill et al., 1995). Traits such as ovary size and egg production
have proven to have substantial heritability and are tied to fitness. The female orgasm has
also proven to have substantial heritability, but more so when elicited through
masturbatory orgasms, indicating a stronger selection for orgasm from heterosexual
intercourse. Traits with a stronger selection have lower heritability and are more closely
linked to fitness. This evidence provides much of the foundation that allows for the
female orgasm to be viewed as an adaptation.
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References
Puts, D. A., & Dawood, K. (2006). The evolution of female orgasm: Adaptation or
byproduct?. Twin Research and Human Genetics, 9(3), 467-472.