Week 10 - Motivation: Reproduction Flashcards
Outline the characteristics of Sex, and some of the possible explanations for its existence?
Reproduction is how evolution directly selects.
It is quite costly and difficult not being asexual (having to find a mate)
Explanation that Two organism reproduction might exist is (1) greater variation by combining genes (more robust off-spring), and (2) having two copies of genes can ‘mask’ copying errors or harmful mutations as it is shared 50/50.
Outline the differences in Sexes and the effect of hormones? Explain the two kinds of effects hormones have on human sexes?
To reproduce you need males and females, where differences are created genetically and hormonally (mostly).
Androgens produce male-typical traits, and Estrogens produce female-typical traits.
Hormones have two effects. (1) Organising effects - building things in a particular way which may influence future behaviour (for example, the building of breasts), and (2) Activating effects which directly influence behaviour (for example, menstrual effects due to shifts in hormones).
Outline the differences between female and male brains?
(Physical Size, composition of white and grey matter, hormones (developing and maternal).
There are many differences between M/F brains, but most are the same (much like bodies). On average, men have large corpus callosums and hypothalamus, and women have larger cingulate cortex and areas of the parietal cortex, which maps onto behavioural difference of M/F.
The M/F brains develop differently. This is due to (1) maternal hormones, where the mother exposed to stress during pregnancy will increase exposure to testosterone (mother’s hormones), and thus develop a more androgenised brain, and
(2) different developing hormones produced by the M/F embryo.
Explain the theory behind Sexual Response Cycles?
Masters and Johnson studied the physiological stages of sexual activity in the 1950’s. Four stages of arousal in both females and males, Excitement, Plateau, Organsm, and Resolution, although female patterns responded more variably. The study is very questionable and the nature of it could explain the results - (50’s, women, measurement devices)
Explain the difference in sex preference and the brain for female and male in sexual behaviour?
The initiation of sexual interests and the reinforcing properties of orgasm (massive release of dopamine), are broadly controlled much like motivated behaviour, and uses similar areas of the brain (hypothalamic and pituitary hormonal control).
The testosterone builds up in the blood stream, and Organsm is the drive reducer.
Males are shown to have more restricted ranges of stimuli for sexual arousal than females. Where females sexuality is much more labile, males usually stick with their preference.
Explain elements of female mating strategies and the Asymmetric characteristics?
There is a divide between males and females based on the sex that invests more into their off-spring/Zypgote, thus gaining a survival advantage.
The sex that invests more from the beginning is usually the female, and is more choosy, and the other must compete for access (Trivers -1972). Not just XX, XY, or in birds males are YY, and females are ZY.
For example, Male emu’s build a big suitable mount for eggs, females lay eggs in the best, and the male incubates and raises (thus can be more choosy).
Explain the many Female Mate preferences that are important for evolution?
Female off-spring would be best if:
(1) Mate who will and can invent in them
(2) Mate who will help care for children (babies are useless, require lots of help - bi-parental care/group).
(3) Mate who is compatible and (4) healthy (suitable and good genes)
In reality, cross-culturally, females are twice as concerned about earning capacity and financial prospects than male partners (at all romantic levels, dating, sex, steady dating, and marriage - resourceful partners). This also occurs for social status, and hardworking/ambition (good prospects).
Females also have to be able to detect investment intentions: (1) willingness - mating dances in animals, and for humans LOVE, culturally widespread, where emotions may be a signal of commitment, engaging in acts (buying flowers) to prove authenticity. (2) caring males, interested in children, where they can tell apparently from the pictures of their faces, and kindness it the biggest indicator. (3) similarity is highly valued, which may account for the preferred age gaps (males develop later than females). (4) Healthy males can be identified by attractiveness cues (symmetry - signals resistance to disease, and masculinity - signals higher levels of testosterone, correlating to strength, but more vulnerable to disease).
Although for human, their is differences in preference (females mean I want a funny guy, males mean I want someone who finds me funny). This may be a fitness indicator, from having a big creative brain.
Explain the mixed mating strategies of females (the dilemma of choosing a mate)?
Woman who have caring, willing, helpful long-term partners are usually lacking benefits with robustness, virility, and dominant traits. Males with best genes don’t have around and look after kids (evolutionary dilemma). To offset this cost/trade-off, females sometimes mate with high-testosterone, but choose the caring males for long-term (for example, the cheating Wrens that mate with one, and stay with another). Therefore Female ‘Cheating’ may be an evolutionary adaption, evidence is females find strong, symmetrical, masculine faces for short-term (as well as smell of symmetrical men), and right before ovulation (most fertile).
Explain Male Mating Strategies?
Human mammal Males are weird, where they almost make no contribution to raising off-spring across many species. Males compete with each other for impregnating rights, by fighting or cunning.
In human society, we use marriage (mate with one for extended period of time). This may have evolved for survivor-ship of children (1) off-spring survival), and (2) paternity certainty (own off-spring).
Men want the same as women (kindness, humour, intelligence, etc), although much more concerned about physical attractiveness, but why does this matter? **
Explain how evolution allows mates to choose based on offspring survival and paternity certainty?
Producing offpsring that need high levels of care may be reliable predictor (1) Off-spring survival. Many birds are bi-parental, although less often true in precocial young (can operate fine from birth). In humans, easy to see how male investments helps reproductive success, as many single mother children often died in hunter-gathered groups. and, (2) Paternity certainty, where evolved mechanism may have ensured this, such as faithfulness (long-term bonds - woman getting jealous about redirected affection (leave-take resources), and males only get jealous about only sex (not their off-spring/genes, cant be selected for), which both make evolutionary sex).
Explain the possible evolutionary explanation for attractiveness? Use primates as an example.
(1) Youth, (2) health, and (3) fertility (especially because humans have concealed ovulation).
E.g. Primates find this concealed ovulation (conspicuous sexual swelling) find this attractive, although human do not. Which may make males stick around, because they are not always aware then they are fertile (to pass on genes).
(1) Signs of youth may indicate the trade-off between reproductive value (longer life-time to mate), and fertility (which is not as highly valued within humans).
Signs include neotany - retention of juvenile features, skin quality, lip fullness, breast shape (sag/perk), and hair quality).
(2) Evidence for health attractiveness includes studies on avergeness (face and body), and symmetry, where these faces are rated more attractive (seen to correlate with health)
(3) Sign of fertility include long-term: Waist to hips ratio, and femininity (facial/bodily), and short-term: facial attractiveness, skin condition and colour, hip swaying, and smell (all change with menstrual cycle).
Describe the relationship between reproductive value and fertility using Chimps?
In primates, older females partners will take preference over younger partners (with higher reproductive value, longer lifetime to mate) as they are better able to care for their young (as this is a big danger for chimp young). There is a trade off between them.
Describe the signs of stable fertility in women? Two examples.
E.g. of stable fertility include The (1) preferred Waist-hip ration is found to be 0.7, to indicate stable fertility, and also previous births (big belly for previously pregnant women).
(2) Femininity is found to be more attractive, so woman tend to these cues, where women with found femininity characteristics are more fertile.
Highlight the role of testosterone in mating? Four examples.
(1) Motivates wooing and mating efforts in men, it (2) raises with the presence of attractive members of the opposite sex, and it (3) drops after the formation of long-term relationships. (4) men (and women) with higher levels of circulating testosterone are more likely to pursue and have extra pair-bond relationships.
