Book/ Chapter 2
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Elements of an evolutionary approach to emotions
The engine that drives evolution has three parts. The first of these Darwin called superabundance:
animals and plants produce more offspring than necessary merely to reproduce themselves. The
second is variation; each offspring is somewhat different than others, and differences are passed
on by heredity. The third is natural selection: characteristics that allow the individual to be
adapted to the environment are selected for; disadvantageous characteristics are selected against.
At the core of natural selection are selection pressures. For humans these are features of the
physical and social environment in which humans evolved, that determined whether or not
individuals survived and reproduced. Some selection pressures involve threats or opportunities
directly related to physical survival. To survive, the individual needs to find food and water, to stay
warm but avoid extreme heat, to avoid predation and disease. Many systems such as our
preferences for sweet foods and aversion to bitter foods, our thermoregulatory systems, our fight
and flight responses, developed in response to these kind of selection pressures.
Intrasexual competition occurs within a sex for access to mates. In many species there is intense
and continual struggle of this kind, often most pronounced among males.
Within intrasexual competition, those traits, whether it be strength, beauty, cunning, emotional
intelligence, or humour, that allow some to prevail over others are more likely to be passed on to
Intersexual competition refers to the process by which one sex selects specific kinds of traits in
the other sex. In humans this is seen in the preference women report for males of higher status.
Preference men show for youth and beauty, because many cues of youth and beauty - full lips,
youthful skin, an hourglass figure, for example – are physical signs of optimal reproduction age.
Adaptations are generally based on traits that allow organism to respond well to specific selection
pressures, and to survive and reproduce.
Consider our dietary likes and dislikes. The typical human has 10 000 taste buds, each with 50
short hair-like structures that convert food particles to an electrochemical signal, and eventually to
our experience of sweet, sour, salty, and bitter tastes. The preference for sweet tastes helps us to
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identify foods of nutritional value, such as foods that provide us with Vitamin C, which humans,
unlike many mammals, cannot synthesize.
When you eat a turnip or cabbage, you are getting a sub-lethal dose of such toxins. Our distaste for
bitter foods helps us avoid these toxins. Interestingly, women are particularly sensitive to bitter
tastes and smells during the first trimester of pregnancy. Sometimes they may experience such
preferences as overwhelming. Profet has proposed that morning sickness of the first three months
of pregnancy may be part of a mechanism to avoid intake of certain toxins that may harm the fetus.
Human babies are very vulnerable and not self-sufficient. They require tremendous care, devotion,
and resources. Evolutionary theorists have argued that our responses to baby-like cues ensure that
parents help their offspring reach the age of viability.
Not all human traits or behaviours are adaptations. Many human traits, from snoring to nervous leg
jiggle, serve no apparent evolutionary function, and are better thought of as byproducts. Moreover,
you should not conclude that all, or even most, human traits emerge de novo, to meet survival- and
reproduction- related problems and opportunities. Evolution is a tinkerer, and often endows old
anatomical and behavioural features with new functions. A trait that acquires a new function like
this is called an exaptation. Andrew uses this principle to propose how facial expressions in
primates, including humans, were developed from reflexes. Many animals have a reflex in which
they flatten their ears when startled, or when approaching another member of their species. Its
original function was to protect their ears.
Humans are not able to retract their ears, but raising their eyebrows seems to derive from the same
movement, and Eibl-Eibesfeldt has shown by inconspicuous filming in many different cultures, that
a brief raising of the eyebrows, lasting a fraction of a second, occurs when people approach one
another during greeting, and in flirting. It is probably a human universal.
See table 2.1
Emotions serve functions
Human traits solve survival- and reproduction-related problems, and help individuals take
advantage of opportunities. So this should be t rue of emotions.
Subsequent accounts, influenced by the theory of evolution, tend to describe emotions in terms of
functions in ways that increase the chances of survival and reproduction. Emotions are adaptations.
One aspect of adaptation is that emotions enable rapid orientation to events in the environment.
Emotions, in effect, interrupt ongoing processes and direct attention to significant threats and
A second general function is organization. Emotions coordinate the cardiovascular and respiratory
systems, the different muscle groups, and facial expressions and experience. This coordination
enables more adaptive response to events in the environment.
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