SEXUAL SELECTION & HUMAN REPRODUCTIVE BEHAVIOUR RELATIONSHIPS SEXUAL SELECTION & HUMAN REPRODUCTIVE BEHAVIOUR

So, some basic (recap) questions on evolutionary theory What, according to evolutionary theory does a behaviour/trait have to be to be present in modern humans?   How can exceptions to this rule be explained? What is the E.E.A. (define and explain)

So, some basic (recap) questions on evolutionary theory What, according to evolutionary theory does a behaviour/trait have to be to be present in modern humans? ADAPTIVE – to improve chances of survival in our environment and thus maximise reproduction potential. Anything which aids of chances, is an improvement…  How can exceptions to this rule be explained? The GENOME LAG – the notion that the rate at which we can physically change (evolve) is slower than (so ‘lags’ behind) the changes we have made to our environment.  What is the E.E.A. (define and explain) The ENVIRONMENT OF EVOLUTIONARY ADAPTATION – the ‘window of time’ in which humans did most of their physical evolving to adapt to the environment. About 3,000,000 – 10,000 yrs ago.

KEY TERMS Natural selection - any characteristic of an individual that increases it’s potential for survival within it’s environment (e.g. social releasers aid survival by making attachment more likely). Sexual selection – a characteristic which is not necessarily beneficial for survival (in fact it can sometimes be detrimental and thus ‘mal-adaptive) but is still favoured by the opposite sex and thus aids the chances of reproduction.

KEY TERMS Anisogamy - The difference (usually referring to size) between male and female gametes (sex cells). This leads to the different mating strategies displayed by males and females. (‘inter’ and ‘intra’ selection). Dimorphism - the differences in physical appearance between males and females of the same species, such as in colour, shape and size. These may be extreme to aid sexual selection e.g. exotic plumes and colours of the male bird of paradise or the male Peacock.

KEY TERMS Intersexual selection (‘Inter’ = ‘between’ the sexes). Females ‘chose’ males. Females have less reproductive potential and so it is important to make the right selection.

KEY TERMS Intrasexual selection (‘Intra’ = ‘within’ the same sex). Males compete with each other to be chosen by females – by impressing or charming them. https://www.youtube.com/watch?v=W7QZnwKqopo Fitness indicator - Anything which, not verbally (animals can’t speak and nor could early man) suggests the presence of ‘good genes’, ‘survival skills’ or ‘parenting potential’

KEY TERMS Neotenous - Childlike features. Facial characteristics which suggest youth (large eyes, big lips, small nose, small chin…

FITNESS INDICATORS So, what should men find attractive (in evolutionary terms) and so females display? https://www.youtube.com/watch?v=2ImZTwYwCug

FITNESS INDICATORS IN FEMALES Hour glass figure. Symetrical facial features. Neotenous facial features. Relative youth.

FITNESS INDICATORS IN MALES Inverted triangle shape Square jaw line Facial (and bodily) hair Tall stature Muscular/athletic Relative maturity

STARTER/PLENARY Place the following key words into a coherent order and elaborate on each (define and/or explain) to form a descriptive paragraph about the relationship between sexual selection and human reproductive behaviour. Fitness indicators Survival Neotenous Inter-sexual selection Intra-sexual competition Anisogamy Adaptive

Human’s reproductive behaviour has adapted over millions of years to aid our species chances of survival. As we are an anisogamous species (the gametes (sex cells) of male and female are different in size and appearance) it has meant that the respective sexes have evolved different traits, characteristics and behaviours when trying to attract a mate and reproduce. As the female is the one who has to invest more time, energy and resources into reproduction (producing an egg, carrying an embryo, childbirth) it stands to reason that she should be the one doing the choosing. Female reproductive potential is limited in comparison to male’s with the number of eggs produced in a lifetime being in the hundreds. Male sperm is much more readily available and easily replenished/produced with millions at any one time. As females choose the male with which to mate (this is known as inter-sexual selection (choice between the sexes) males compete for the right to be picked (intra-sexual competition). This has led to evolved physical differences between the sexes with males being bigger and stronger than the females (dimorphism). This increased size and muscle acts as a fitness indicator of the male’s reproductive potential (a non-verbal cue about the viability of mating potential). Other male fitness indicators include relative age (the male is seen as attractive if a little older that the female), angular features and facial and body hair. These are all indicators of maturity. Females on the other hand exhibit fitness indicators such as an hour glass figure which signifies an ability to bare and nourish children whilst initially (marrow waist) being unlikely to be pregnant with another man’s offspring. Females are also seen as attractive if they have neotenous features (child-like) which signify youth and health and a long reproductive potential ahead of them.

Secret of the sexes film https://www.youtube.com/watch?v=oNjKg3FrnxU

Research Evidence Cunningham et al., (1995) found that within and between cultures, individuals may display variance in response to specific features, but will respond in a similar manner to the features as a whole. They presented males from 4 ethnic-cultural groups with Asian, black, Hispanic, and white female faces. All males were attracted to large eyes, small noses, high cheekbones, small chin and a large smile. THUS SUPPORTING THE PREFERANCE BY MALES TO NEOTENOUS FEATURES IN FEMALES.

Research Evidence Singh (1993) In girls of the same body weight, those with lower WHR’s (feminised) were rated (by both males and females) as being the healthiest, most attractive and being most reproductively viable. THUS SUPPORTING THE PREFERANCE TO THE HOUR GLASS FIGURE.

Research Evidence BUSS (1989) studied partner preferences in 33 different countries 10,000 men & women aged 16-28 were asked about their preferences. In all cultures he found: Men valued physical attractiveness more than women Men valued women younger than themselves Women valued financial success & ambition more.

Research Evidence - Waynforth and Dunbar (1995) W&D conducted a content analysis of 900 Lonely Hearts ads in a variety of US newspapers and magazines. They found: Age Males asked for females 1-12yrs younger than them; females asked for males 2-7yrs older 42% of men wanted a younger partner; 25% of women wanted a younger partner Attractiveness Males mentioned own attractiveness 1.4x less than females but asked asked for attractiveness 2x as often as females Resources Males mentioned own wealth 1.7x more than females; Females asked for wealth 4.5x more than Males https://prezi.com/htehb8qtnz_i/wayneforth-dunbar-1995/

CONTENT ANALYSIS An indirect observation where you analyse artefacts (something made by man) such as adverts, lyrics, films. You turn qualitative data into quantitative data through the use of a coding system.

Research Evidence Clark and Hatfield (1989) https://www.youtube.com/watch?v=rYjjKabrDpQ

Research Evidence And a final note…. Clark and Hatfield (1989) came up with a novel way to test for differences in preferred mating strategies between males and females. They set up a field experiment where a confederate (always an attractive, young student (m/f) would approach a member of the opposite sex on a college campus and proposition them with three questions: “Would you like…. to go out tonight? to come back to my place? to have sex with me?

Research Evidence The responses to the three questions were: “Would you like…. to go out tonight? - 50% of both males and females agreed to this to come back to my place? - 69% of males would but only 6% of females would to have sex with me? - 0% of females agreed but 75% of males did