Human Mating Strategies

Central Question Can humans be shown to mate in a manner consistent with the hypotheses surrounding mate choice by either perception of genetic quality or of ability to provide resources?

Human Reproductive Investment 1. Female investment in offspring – very high Male investment in offspring – variable 2. Reproductive life Female Male 10 20 30 40 50 60 70 80

Human Reproductive Investment 3. Reproductive “down time” pregnant reproductively ‘available’ Female 10 20 30 40 Female Male 10 20 30 40 50 60 70 80

Three components to consider 1) Human mating is strategic 2) Mating strategy is context dependent 3) Men and women have faced different problems and will have different strategies

Look at sexual strategies that males and females might pursue Look in the context of a) short term mating b) long term mating

Elements of female strategy Type of mating Elements of male strategy -number of partners -immediate resource extraction -identifying sexually accessible women -evaluating short-term mates as potential long term maes Short-term -minimize cost, risk, commitment -attain men with high quality genes -cultivate potential back-up mates -identify women who are fertile -paternity confidence -identify men willing & able to invest Long-term -assessing a woman’s reproductive value -physical protection from aggression -identify men who will commit -identify women with parenting skills -identify men with good parenting skills -attaining women with high quality genes -attaining men with high quality genes

Hypotheses arising from previous slide 1) Short term mating is more important for men than women Very likely Very unlikely

Question: If you could mate with a member of the opposite sex who was no more or less attractive than your permanent mate and there was no risk of disease, discovery or forming a permanent liaison, would you do it? 100 80 60 40 20 Probably/certainly not - Females - 91% - Males - 50% - Males - Females Certainly would Probably would Probably not Certainly not

Hypotheses arising from previous slide 2) Men seeking a short term mate will solve the problem of identifying women who are sexually accessible -survey of 44 men and 42 women -survey of 44 men and 42 women Men – value experience and promiscuity in short term but not long term mate Women–experience and promiscuity not desirable in either mate

Hypotheses arising from previous slide 3) Men seeking a short term mate will minimize commitment and investment -survey of 44 men and 42 women Men – value commitment and investment in long term but not short term mate Women–commitment and investment desirable in either mate

Hypotheses arising from previous slide 4/5) Men seeking a short term mate will solve the problem of identifying fertile women while men seeking a long term mate will solve the problem of identifying reproductively valuable women Fertile – refers to the probability that a woman can conceive a child Reproductive value – expected future reproduction Generally, men should prefer mates who are younger than themselves

Age preference in mates in males and females

Hypotheses arising from previous slide 6) Men seeking a long term mate will solve the problem of paternity confidence Value placed on chastity

Hypotheses arising from previous slide 7) Women seeking a short term mate will prefer men willing to impart immediate resources -survey of 44 men and 42 women Women – place greater importance on gift giving in a short term mate - especially negative to ‘stingy’ men

Hypotheses arising from previous slide 8) Women will be more selective than men in choosing a short term mate -survey of 44 men and 42 women -women are seen as engaging in more prospective long term mate assessing Women – found short term mates who are already in some relationship to be undesirable.

Hypotheses arising from previous slide 9) Women seeking a long term mate will prefer men who can provide resources for offspring

Hypotheses arising from previous slide 9) Women seeking a long term mate will prefer men who can provide resources for offspring

Hypotheses arising from previous slide 10) Both sexes should value attractiveness in a mate (good genes)

Hypothesis Proportion of cultures supporting hypothesis Women value earning potential more than men Women value ambition and industriousness more than men Men value physical attributes more than women Men value chastity more than women Men prefer women younger than themselves 0 25 50 75 100 Proportion of cultures supporting hypothesis

Valued Disliked 3 Short term Long term -3 Physically attractive Sexually Experienced Physically unattractive Good looking Promiscuous Committment Low sex drive No sexual Exp Sex appeal Prudish 3 Short term Long term -3

3 Short term Long term -3 Promising career? Good financial prospects Likely to succeed Reliable career Unable to support Poor Uneducated High earnings? No ambition 3 Short term Long term -3

Most primates Males  concentration on mating effort Females  concentration on parental effort

Dominance in a Social Group Environmental constraints Group structure Male strategies Female strategies

Dominance in a Social Group Underlying principle: Higher status males  more copulations & more offspring

Dominance in a Social Group Kipsigis # wives Acres owned

Dominance in Social Group 12 - 14 Age at puberty 15 - 16 17 - 19 Bride price 52-61 62-71 72-81 82-91 Decade

Ecology of human mating systems Starvation Food storage/trade Protein deficiency Subsistence Pathogens Female contribution Rain predictibility Marriage system Population density Rainfall extremes Mobility Temperature extremes Group size

Ecology of human mating systems Starvation Food storage/trade Protein deficiency Subsistence Pathogens Female contribution Rain predictibility Marriage system Population density Rainfall extremes Mobility Temperature extremes Group size

Ecology of human mating systems Starvation Food storage/trade Protein deficiency Subsistence Pathogens Female contribution Rain predictibility Marriage system Population density Rainfall extremes Mobility Temperature extremes Group size

Ecology of human mating systems If there are no resources??? Unokai – Yanomami warriors (involved in a killing) More wives earlier in life Wives Children Wives Unokai Non-Unokai 20-24 25-30 31-40 >40 Age

2. Good genes models Fluctuating Asymmetry Horns in oribi - Ourebia ourebia

Harem size Symmetric Asymmetric Damaged

Facial Symmetry - Measurement

Attractiveness – Facial Symmetry Left Mirror Right Mirror

Attractiveness – Facial Symmetry

Symmetry and Health 1.0 Men Women 0.5 -.05 Correlation -.05 Men Women Correlation Assymetry/Health Assymetry/Attractiveness Health/Attractiveness

Symmetry and Health Own sex faces Opposite sex faces Mean Health Rating Normal Symmetrical

Symmetry Preferences and Conception Prefer Symmetry Prefer Asymmetry Probability of Conception

SPERM COMPETITION

Human mating systems Sperm competition How monogamous is monogamy? Indigo bunting Within pair Extra-pair 12 Days before egglaying

Sperm Competition in Humans Criteria Multiple matings with different males within 5 days -83% of women with >5 sexual partners per year report concurrence -9% of all women & 15% of women (16-24) – concurrent relationships

Human mating systems Sperm competition When does it occur? 1. Adolescent courtship Triobrand Islands

Human mating systems Sperm competition When does it occur? 2. Facultative polyandry Polyandry polyandry polygyny monogamy

Human mating systems Sperm competition When does it occur? 2. Facultative polyandry Polyandry polyandry polygyny monogamy Facultative Polyandry universal moderate occasional uncommon

Human mating systems Sperm competition Why should females be polyandrous? 1. Good genes 2. Genetic Diversity 3. Fertility Backup - 25% of couples - sterility (35% -male) 4. Material Resources females mate extramaritally more often with men of higher socioeconomic status females mate extramaritally more often with men older than their primary mate

Human mating systems Sperm competition What attributes of humans may have evolved in context of sperm competition? Males 1. Mating patterns - most common -monogamy (with extramarital mating?) -only if cost of any extramarital tactic is free or < cost of supporting second mate

Human mating systems Sperm competition What attributes of humans may have evolved in context of sperm competition? Males 2. Sexual Jealousy and Paternity Assurance Spousal homocide related to sexual jealousy USA - 33% Africa (several studies) - 45%

Human mating systems Sperm competition What attributes of humans may have evolved in context of sperm competition? Females 1. Cryptic ovulation and continuous sexual receptivity Most primates Humans

Human mating systems Sperm competition What attributes of humans may have evolved in context of sperm competition? Females 2. Perennially obvious breasts

Central Question Can humans be shown to mate in a manner consistent with the hypotheses surrounding mate choice by either perception of genetic quality or of ability to provide resources? But we need to be careful in interpreting data!

DONE!