Relationships - Sexual Selection And Human Reproduction Flashcards
What doe sexual selection argue?
Sexual selection argues that if a characteristic increases the chance of reproduction then the characteristic will be adaptive because the animal will have more offspring
What is Anisogamy?
An organism that produces sex cells
What does it mean that humans are anisogamous?
they produce gametes (reproductive cells) of different sizes
Why are there 2 different types of sexual selection?
anisogamous species the female invests more energy (giving birth) in reproduction than males, so it leads to 2 different types of sexual selection.
What are the 2 different types of sexual selection?
Inter sexual selection
Intra sexual selection
What is inter sexual selection?
usually females - this is where one sex chooses traits that they desire in the other - this selection is between the sexes - quality strategy
What is intra sexual selection?
Intra-sexual selection - usually males - since there is competition between members of the same sex so they tend to have sex with as many people as possible - this selection is within each sex - indiscriminate
What factors might inter sexual selection may be interested in?
What may this lead to?
indicators such as economic resources and genetic fitness as a result we are programmed to exhibit these characteristics to try and pass on our genes
What is SST (Sexual Strategies Theory)
Sexual strategies theory (SST) is an evolutionary theory of mating strategies that both males and females adopt under different circumstances
What is unique about Sexual strategies theory?
It includes multiple motives each individual may have eg short term vs long term ,mating as well as when and why different motives may be different
How many different SSTs are there?
6
State the 6 SST theories?
Sexy sons hypothesis
Handicap hypothesis
Sexual dimorphism
Sperm competition
Sneak copulation
Symmetry
In SST all theories are either based on … and is either …
These will be referred to as the audience of a study
Male/females
Inter/intra
What is the audience of the sexy sons hypothesis?
Female
Inter
What is the audience of the handicap hypothesis?
Inter/female
What is the audience of sperm competition?
Intra/male
What is the audience of sneak copulation?
Intra / male
What is the audience of symmetry?
Inter/both
What year was Fischer’s sexy sons hypothesis made in?
1930
When was Zahavi’s handicap hypothesis made?
1975
When was Cartwright’s symmetry theory made?
2000
Explain Fischer’s sexy sons hypothesis (everything)
…
Fishers (1930) - Sexy sons hypothesis (Inter) Female strategies
A women may choose a man because he has a characteristic that she wants so that all male children that she has will hopefully have that gene
Runway process - over generations a characteristic becomes more pronounced
The theory ends when the the trait becomes too costly or female preference change
Explain Zahavi’s handicap hypothesis? (Everything)
Zahavi’s (1975) - handicap hypothesis (Inter) Female strategies
A women chooses a man with handicaps because it advertising his ability to thrive despite handicaps demonstrating genetic superiority
Eg females finding males attractive who drinks or takes drugs in large amounts because it demonstrates an ability to handle toxins which is a sign of genetic fitness
What type of theory is SST?
Evolutionary theory
Explain the Sexual Dimorphism theory? (Everything)
Sexual dimorphism (Intra) Male strategies
This is the different characteristics that males and females possess that may make them look like a better option
Eg males are on average 14% larger than females
This may also include secondary sexual characteristics
Eg males have deeper voices and facial hair (which indicates more testosterone)
Eg females - breasts hip to waist ratio, smoother skin
Explain the sperm competition theory?
Sperm competition (intra) Male strategies
Physical size matters for men
And behaviourally aggressive men may be more likely to reproduce as they are more able to fight off other men
This is complete by producing larger testicles, bigger ejaculations and faster swimming sperm
Explain sneak copulation theory? (Everything)
Sneak copulation (intra) Male strategies
Males may decide mate with with females other than their partner if given the opportunity as increases their chances of reproductive success
Male/Women may gain from this as there is now a wider genetic diversity for their children, increasing survival chances
Women could also benefit as they may be able to live with a resource rich male, whilst copulating with a genetically fit stud (viable, fertile male)
Explain Cartwright’s symmetry theory?
Cartwright (2000) Symmetry (Inter)
Cartwright (2000) both men and women prefer symmetrical faces
This leads to the finding that symmetry equates with reproductive fitness
Cartwright also found that women with symmetrical breasts are more fertile
AND women with a more symmetrical partner have the most orgasms
What are the positive evaluations of Sexual Strategies Theory?
‘What do women want”
Research support for inter sexual selection
Curves in the right places
“Ovulating lap dancers”
“Lonely hearts”
What are the negative evaluations of Sexual Strategies Theory?
Oversimplified
“Choosey old men”
Explanations ignores social and cultural influences
Explain the positive evaluation of SST: “what do women want?
Buss (1989)
Buss did a large cross cultural study into human mating preferences
10,000 people in 37 cultures (33 countries)
Found consistent sex differences
Women want:
Good financial provider
Ambitious
Tall and strong
Older than them
Symmetrical face and body
Men want:
Younger
Chastity
Healthy
Physically symmetrical
Good waist to hip ratio
Explain the positive evaluation of SST: Research support for inter sexual selection
Clark and Hatfield (1989)
Explain the positive evaluation of SST: curves in the right places
Singh identified a waist to hip ratio as a universally major determinant of attractiveness
They used data from the past 50 years of beauty contest winners and playboy centrefold
Small waist and full hips were a consistent feature
Whilst breast size, overall body weight and physiques varied over time
Optimal waist to hip ratio was 0.7. (This is also associated with fertility)…
Explain the positive evaluation of SST: “Ovulating lap dancers”
Most female mammals display oestrus to alert males to receptivity
In humans oestrus is hidden or is it?
He found that lap dancers who were ovulating naturally earned more tips that the pill taking dancers
When they were in non fertile periods they earned the same amount of tips
What are the negative evaluations of SST: oversimplifying
The evolutionary explanation only explains heterosexuality and that all relationships are sexual
It can’t explain homosexual couples or coup[les that decide not to have
Explain the negative evaluation of SST: “choosey old men”
Campos et al (2002)
He also studied personal ads
He suggested that as women aged, they become less demanding
Whereas men become more demanding with age
Explain the negative evaluation of SST: ignores social and cultural differences?
Over the last 100 years what has been viewed as attractive has changed (influenced by changing social norms of sexual behaviour)
Since evolution is a slow process attraction can’t be completely evolutionary
Bereczkei (1997) - women in the workplace don’t rely on men - So women are no longer resource-orientated
Chang et al (2011) compared partner preferences in China over 25 years and found differences to results that were found in the west
Describe the male sex cells?
X/Y
Has a head and mitochondria, flagella and acrosome
It is small
It gets propelled through the mucus by its tail
Describe the female sex cells?
XX
Large
Is static
Explain the Positive Evaluation: Lonley Hearts
Content analysis of personalised ads in 4 newspapers
479 male ads and 402 female ads
Males:
There was an indication of material wealth 1.7 times more than women
Men ages 40-49 most likely to express preferences for female fecundity (ability to produce young in great numbers)
Women:
Twice as likely as males to advertise their physical attractiveness
They demanded wealth in a partner 4.5 times more than men
They mentioned youth more
