Examine one evolutionary explanation of
behaviour
Introduction
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State what you are doing in the essay
This response will attempt to uncover the assumptions and interrelationships of the evolutionary explanation for
emotion, in particular, disgust.
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Define evolution
Evolution is the changing in the inherited traits of a species over time.
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Describe the theory of evolution
Evolutionary psychology is at the biological level of analysis and aims to explain all behaviour by evolutionary
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means.
Charles Darwin – the father of evolutionary psychology – proposed the theory of evolution.
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He suggested those who adapt best to environmental challenges will have a greater chance of survival,
reproduction, and passing on genes.
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Natural selection refers to the idea that members of a species that survive competition and breed will have
characteristics better suited to the environment and are more likely to pass on these traits.
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Natural selection results in successive generations of a species developing characteristics that make it more
competitive in its field – adaptation.
Explain the principles of evolution with behaviour; make a link to the question
o If it is assumed that a predisposition for certain behaviours is inherited through genetics, and that the principles
of evolution dictate that genetically based behaviours of an individual who has reproduced are passed on (while
genetically based behaviours of unsuccessful individuals are lost over time), then behaviours observed today
should have an evolutionary explanation.
In essence, if behaviour exists in humans today, then it must have in the past helped in human survival and
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reproduction.
Behaviour that has helped a species survive, thus reproduce is described as adaptive.
The key assumption of all evolutionary psychological research is that human behaviour must have been
adaptive under some circumstances in the past.
Body
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Introduce the topic, signpost to the examiner
In this essay, the behaviour which will be examined in terms of an evolutionary explanation/bases is the study of
emotions, in particular disgust.
This is connected to the study conducted by Fessler in 2006.
Study 1: Fessler (2006)
Background:
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In the first trimester of pregnancy, hormones lower women’s immune systems so that it does not fight the new
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foreign genetic material in the womb.
He argues that the emotion of disgust allowed our ancestors to survive long enough to produce offspring, who in
turn passed the same sensitivities to us.
Aim:
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Fessler hypothesised that disgust helps to compensate for the suppressed immune system.
Method:
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He asked 496 healthy pregnant women between ages 18 – 50 to rank 32 potentially disgusting scenarios.
For example, maggots on a piece of meat in an outdoor waste bin.
Before asking the women to rank the level of disgust in the scenarios, Fessler asked questions to determine
whether they were experiencing morning sickness.
Results:
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Women in their first trimester scored higher in disgust sensitivity than women in the second and third trimesters.
When Fessler controlled the study for morning sickness, the response only applied to scenarios involving food.
Conclusion:
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Fessler explained this in terms of the large extent of dangerous diseases, which are food-borne.
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Being pickier with food would also help humans avoid diseases that could harm unborn offspring, and thus,
threaten the species.
Natural selection may have helped human ancestors to be pickier with food to compensate for increased
susceptibility to disease.
Connection of study to question
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Fessler’s study supports that disgust may be an evolutionary behaviour as it may assist reproduction of offspring
and protection against disease, thus having a greater chance of surviving or living a longer life, having children
passing on genes to their offspring.
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This study supports the role of disgust in aiding reproduction, and thus, as an evolutionary behaviour.
Study 2: Curtis et al. (2004)
Method:
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Tested whether there were patterns in disgust responses via an online survey
77 000 participants from 165 countries.
Participants were asked to rank their level of disgust for 20 images.
Within the 20 images were 7 pairs where one was infectious or harmful to the immune system and the other was
similar but non-infectious.
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For example, one image was a plate of bodily fluid and its pair was a plate of blue viscous liquid.
Results:
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The disgust reaction was strongest for images which threatened the immune system.
Disgust also decreased with age and women had higher disgust reactions than men.
Connection of study to question
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These findings suggest that disgust is evolutionary.
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Natural selection may have helped human ancestors to be more disgusted at things which threatened the
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immune system to avoid things that could potentially lead to diseases or sickness.
This would allow them better chances of survival and reproduction to pass on their genes.
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The decrease of disgust with age may be explained by the fact that the older a member of a species, the less likely
they are to reproduce.
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Therefore, their disgust reaction (that can prevent death of offspring) decreases.
The stronger disgust reaction of women may be the result of natural selection and adaptation.
As women are the carriers for offspring, they have a stronger disgust reaction so as not to threaten the lives of
unborn offspring and consequently, the species.
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This study supports the role of disgust in aiding reproduction, and thus, as an evolutionary behaviour.
Conclusion
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Darwin’s theory of evolution is based on the key assumptions
o Natural selection - those who adapt best to environmental challenges will have characteristics better suited to
the environment and are more likely to reproduce and pass on these traits.
Natural selection results in adaptation – successive generations of a species developing characteristics that
o
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make it more competitive in its field.
The principle of evolution is based on how our genes mutate and change, with those that are advantageous being
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passed down through a process of natural selection.
There is an evolutionary explanation of disgust
Fessler (2006) showed that disgust may be an evolutionary behaviour as it may assist reproduction of offspring
by compensating for a suppressed immune system.
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Curtis et al. (2004) found that the disgust reaction may help to prevent sicknesses.
Research suggests that disgust aids the survival of the human species and is therefore an evolutionary
behaviour.