Attractiveness, Mate Choice, & Human Mating Systems

What seems to be the ancestral mating pattern of humans (based on morphology)?

● Slight body dimorphism ● No canine dimorphism ● Slightly enlarged testes → Means ancestral humans were mildly polygynous (one male, 2–3 females).

What is the most common mating system culturally?

Across societies: polygyny is permitted in ~80% of cultures. However, most relationships are monogamous.

What is the most common form of human union?

Despite cultural permission for polygyny, the most common actual unions are: ● Monogamous marriages (Most men cannot afford multiple wives.)

When is polyandry likely to be practiced?

Occurs where resources are extremely scarce (e.g., Himalayas). Fraternal polyandry helps keep land together. Usually paired with beliefs in partible paternity.

Two models for why polygyny occurs, Which is more supported in humans?

1. Polygyny Threshold (PT) Model: ○ Women benefit from joining a man with more resources, even if he already has a wife.

2. Male Coercion (MC) Model: ○ Men use power/coercion to monopolize women. ○ Supported when women’s fertility doesn’t benefit from polygyny.

The Dogon case: MC model has stronger support. (Polygynous women had more births but lower survival; men benefit more.)

Is polygyny more beneficial for males or females?

● More beneficial for males → increases male reproductive skew. ● Rarely beneficial for females.

Why is polygyny so prevalent?

● Cultural practices that control female sexuality (e.g., FGM, menstrual seclusion). ● Older men monopolize resources. ● Creates artificial scarcity of marriageable men for young women.

Three types of monogamy

1. Social monogamy (marriage)

2. Sexual monogamy (exclusive sex)

3. Genetic monogamy (exclusive reproduction) — and your slides note that extramarital sex is quite common in many cultures.

Explanations for how humans transitioned from mild polygyny to monogamy

1. Leveling hypothesis: ○ Weapons made fighting more dangerous → dominant males can’t enforce polygyny.

2. Trade-off hypothesis: ○ Cooperation between males becomes more important (warfare, hunting). ○ Reduces benefits of aggressive competition.

3. Ecological hypothesis: ○ Females become more spread out → males can't guard multiple females.

Why paternal provisioning is an unlikely explanation — but how it may explain modern pair bonding

● Unlikely as the main evolutionary driver of monogamy (because polygyny still widespread and often males don’t provide much).

● BUT paternal provisioning may explain modern pair bonding:

○ During the weaning phase, Hadza men’s foraging compensates for women’s reduced ability to feed children → improves child survival.paternal investment encourages stable partnerships, enhancing offspring survival and reproductive success.

Types of paternal care

● Direct care: holding, grooming, playing, proximity

● Indirect care: provisioning, providing resources

In which mating systems do you see the most and least paternal care, and why?

● Most paternal care: ○ Polyandry & monogamy (men invest more when paternity certainty is high). ● Least paternal care: ○ Polygyny (men spread investment across multiple wives; r-selected strategy).

Why are females usually the choosier sex?

Because females invest more in reproduction (pregnancy, lactation) → higher cost of a bad mate. This is standard intersexual selection.

What direct and indirect benefits might females be attracted to?

● Direct benefits: ○ Food, protection, resources, care for offspring ○ Resource-holding potential (RHP) ● Indirect benefits (good genes): ○ Honest signals of health, immunity, developmental stability ○ Traits that indicate male can survive despite costly features (handicap hypothesis)

Two traits reliably considered attractive cross-culturally (in both males & females)

1. Averageness: easier for the brain to process (perceptual bias) + may indicate health.

2. Symmetry: honest signal of ability to handle developmental stress.

Why might BMI preferences differ in different conditions?

In resource-poor societies → higher BMI preferred (associated with health & access to resources). ● In Western societies → very low BMIs are preferred due to media influence, thinness linked with wealth/status. ● Immigrants shift preference after expoure to Western norms.

Why would waist-to-hip ratio (WHR) relate to attractiveness in females?

● It signals fat distribution, not total fat. ● Hips store fat needed for gestation and lactation. ● WHR ~0.7 often signals fertility, though not universal.

What did beards appear to have evolved for?

● Age ● Status ● Aggressiveness NOT with attractiveness. Therefore: Beards likely evolved via intrasexual selection — signaling dominance to other men, not to attract women.

What is the tradeoff females may face when choosing a mate, and what influences that choice?

The classic “Dad or Cad” tradeoff:

● Masculine men = good genes but less parental investment

● Less masculine men = lower genetic benefits but better fathers Preferences shift with:

● Ovulation

● Whether seeking short-term vs long-term partner

● Parasite load in environment

● Woman’s own status/attractiveness