Trait or set of traits that evolved because they serve some function.
o Increases reproductive success
How can we recognize an adaptation
o Not all things are adaptive (example why is blood red? Its not that it's adaptive its just due to
interactions of haemoglobin)
o Reverse engineering
Go from form to function (infer function).
Example beaks of different shapes (why?) --> to eat different foods thus allowing
Criteria of good design
Example: arctic hare fur colour change in summer and winter
The phenomenon is only produced under specific circumstances
Example: arctic hare fur colour doesn't change in response to hunger
Favourable benefit to cost ratio
Are the effects of phenomenon positive and more beneficial than other behaviours
Is proposed function the simplest (most parsimonious) explanation
Is there something that would better explain the phenomenon.
Many explanations in psych fail this
o Protection from noxious substances
Keep us away and prevent us from consuming things that would make us sick
We can have the same mechanisms being used in other domains
o Example: we can have physical disgust, sexual disgust, moral disgust, etc
o Natural selection takes things that were there before and can reuse them in other domains.
o If you present two people with 2 similar stimuli but one is more associated with disease the
one that is more associated with disease will be associated with more disgust
o People who need to be more concerned with disease will show greater disgust.
o Two pictures some that are more related to disease others that are less associated with
disease and had to rate them as more or less disgusting
o Found women give higher ratings of disgust than do males.
Is it reliable?
o It is fairly reliably triggered by things that are disgusting but you can train yourself to no
longer be disgusted Is it specific?
o Is it only produced in response to noxious substances?
Not usually initiated in response to good or inert things.
Is it efficient?
o When you experience disgust you tend to avoid the thing that disgust you fairly effectively
o Are there better explanations out there?
Traits that have no function that are caused by some other trait that is adaptive (blood example).
Foot print shape?
o Foot print isn't adaptive but it is a byproduct of the shape of the foot that is well developed to
Function of blindspot?
o Not just due to design of the eye
o No function (lust) vs shedding old sperm.
Requires testing between them
How they come about
o Inevitably produced
Breathing out CO2
o Trait not being subject to selective.
o Traits 'piggyback' on other traits
A trait that is strongly selected for what has other traits associated with it those
associated traits will increase as well
Example: aggressive mating in male roosters (kill 50% of their mates) that may be linked