Evolutionary - SAQ Flashcards
Evolution
The process by which organisms change from generation to generation as a result of a change in heritable characteristics.
Biological organisms have a drive for what?
Need to survive
Reproduce
Differential fitness
There is considerable variation in the traits of individual organisms from the same population.
Organisms having different traits are adapted to their environment to varying degrees - some better, some worse.
Survival of the fittest
Those organisms that are well adapted to the environment have higher chances of surviving and producing offspring.
Organisms that are less adapted die out or are unable to produce offspring.
Natural selection
Gradually as those organisms that are less adapted do not pass on their genes, those genes disappear from the population gene pool.
More adapted organisms produce more offspring, so their genes in the gene pool get stronger.
What does the evolution theory explain?
It explains the variety of species and their modification that we observe in the world by placing all these species into a developmental historical perspective. It also traces back common ancestors for all organisms, including humans.
What does evolutionary psychology explain?
Attempts to explain psychological traits or behaviours as adaptations.
Evolutionary explanations in psychology have been proposed for a wide range of phenomonena.
Sexual selection
How the ‘best mate’ is chosen to produce and protect the most healthy offspring.
This links as well with intersexual selection which is competition between sex (usually males) for access to mates.
Usually the ‘strong’ ends up being able to pass their genes.
Members of one sex (usually females) then choose members of the other sex based on a specific characteristic.
Study used for evolution
Wedekind
When was Wedekind?
1995
What does MHC stand for?
Major Histocompatibility Complex
What is MHC?
A group of genes that play an important role in the immune system
Every individual has quite a unique MHC footprint
MHC genes make molecules that enable the immune system to recognise pathogens
The more diverse the MHC genes of the parents the stronger the immune system of the offspring
What did Wedekind argue?
Our “smell” is based on our MHC and it is best for a woman to choose a mating partner who has a different smell in order to maximize the immune system of her child.
How are MHC genes expressed?
MHC genes are expressed co-dominantly – that is, that we inherit the MHC alleles from both of our parents and they are expressed equally.
Why is it good to recognise MHC genes?
It would be beneficial, therefore, to have evolved systems of recognising individuals with different MHC genes and preferentially selecting them to breed with to maximise immune responses.
Aim of Wedekind (1995)
To determine whether one’s MHC would affect mate choice.
Sample of Wedekind (1995)
49 female and 44 male students from the University of Bern, Switzerland
What information was taken from the participants?
Each participant was “typed” for their MHC, and a wide variance of MHC was included in the sample.
It was noted if the women were taking oral contraceptives.
The students probably did not know each other as they were from different courses
What were the men asked to do?
The men were asked to wear a T-shirt for two nights and to keep the T-shirt in an open plastic bag during the day.
They were given perfume-free detergent to wash clothes and bedclothes and perfume-free soap for showering.
They were asked not to use any deodorants or perfumes, to refrain from smoking tobacco or drinking alcohol, to avoid all spicy foods and to not engage in any sexual activity.
What were the women asked to do?
Two days later, the women were asked to rank the smell of 7 t-shirts, each in a cardboard box with a “smelling hole.”
The women were tested whenever possible in the second week after the beginning of menstruation, as women appear to be most odour-sensitive at this time.
The women were also asked to prepare themselves for the experiment by using a nose spray for the 14 days before the experiment to support regeneration of the nasal mucous membrane if necessary – as well as a preventive measure against colds or flu.
Each woman was also given a copy of Süskind’s novel Perfume to sensitive their smell perception.
Results of Wedekind (1995)
Women scored male body odours as more pleasant when they differed from their own MHC than when they were more similar.
This difference in odour assessment was reversed when the women rating the odours were taking oral contraceptives.
This suggests that the MHC may influence human mate choice.
Linking it back to evolution
This suggests that natural selection may play a role in human mate selection. If the woman’s mate has a different MHC allele, then both his allele and her allele will be inherited and expressed by a child, thus increasing its immune system and chances of survival.
What to know for evolution
Evolution
Differential fitness
Survival of the fittest
Natural selection
What does the evolution theory explain?
What does evolutionary psychology explain?
Sexual selection
MHC
Wedekind (1995)
