Human Mating Systems

Non-human primates provide a _ not _

Model, rules

Mating preferences are

Strongly culturally mediated (culture is a better predictor of human mating behaviours but we CAN learn from evolutionary theory)- changing rapidly

Examples of mating preferences changing rapidly

Globalization and birth control

What lies to people tell when trying to study mating

Under/over reporting sexual activities and partners

What are the four reasons why human mating patterns are hard to study

Non-human primates provide a model not rules, mating preferences are strongly culturally mediated, people lie when asked, and human sexuality and romantic relationships are complicated

Lower fitness traits of inbred offspring

Recessive traits can become expressed (fatal diseases like Tay-Sachs)

Evolved mechanisms to avoid inbreeding

• Dispersal from natal groups

• Social and psychological mechanism

• Strong inhibition against mating with close kin

• NHP remaining in natal groups or attain sexual maturity prior to dispersal rarely mate with close relatives - one mechanism seems to be age related

Mechanism of inbreeding avoidance in chimpanzees

Rarely mate with much older males; males seem uninterested in very young females

In some cultures mating with distant relatives is

Normal, but never close relatives

Wives age of adoption and fertility rate is

Positively correlated

Male and female fertility differs with

Age (female peaks earlier and declines faster)

Male and female age of peak fertility

Female (25), male (30)

Paternal investment is

Highly variable

Males should prefer females who are

Younger than them and have indicators of high fertility (physical appearance)

Sexual fidelity should be important to

Males

Maternal investment in females is

Always high

When choosing mates, females

Should be very selective (provide resources for them and offspring)

Females have minimal concern about

Age (show preference for older males)

In females fidelity should be important but

Wont care as much as males

Females should be more

Conservative in initiating sexual relationships

Values seen in both sexes

Value, physical attraction, love, stability, pleasantness, sociability and overall compatibility (important because of prolonged connection)

Marriage:

• Usually monogamous

• Investment by both male and female in offspring

• Defines social status of offspring

Functions of marriage

• Minimize male-male competition

• Protect females from mating aggression

• Maximize paternity certainty (not absolutely)

Marriage is variable in

• Number of mates and children

• How marriages are regulated (official, arranged, terminated)

• Relationships between individuals

• Where they live

Humans are not

Exclusively monogamous

General polygyny is

Regular

Mild Polygyny is

The most common

In Polygyny

Men have multiple wives

Variability in polygynous males

Hunting ability, wealth, political rank all correlated with RS

Wealth and power in Polygyny

Enables some men to attract more mates and provide them with resources

In post-agricultural societies

Potential for extreme polygyny

Even with polygyny

• actual rates vary widely

• spectrum between being tolerated and being the norm

• men have fewer wives than they aspire to

Even with monogamy

Extramarital sex is not infrequent

• biological father is not the mother’s husband

• non-paternity highly variable - 10%

Serial monogamy and frequent divorce

Major cause of marriage termination across cultures is

Infidelity

Infidelity does appear to be more common in

Males than females (female infidelity matters more from a bio perspective)

What is bridewealth/ bride price

Money paid to the brides family by the groom or his family for the loss of her labour (more common in polygynous societies because men may marry other wives and divert resources to other offspring)

What is a dowry

• Money paid by the family of the bride to the groom/his family

• rare but more common in highly stratified societies and monogamous societies

• strategy to marry females to higher status males whose status will be passed on to the offspring

Polygyny: Kipsigis

• Kenya

• Females marry in late teens

• Males marry in their twenties

• Many marriages are arranged

• Bridewealth is paid in livestock and cash

• Competition for females is strong (normally receive several offers)

Polygynous females

• Competition among wives fro their mate’s resources

• Prefer males who can offer the largest amount of land per wife, regardless of number of wives

• Males whose Co-wives have produced the fewest children

• Those women who balance these two considerations have the highest RS

In Kipsigis males there is a correlation between

Land and RS

What is Polyandry

One woman is married to several men

• Rare (0.5% of human societies)

• Men in polyandrous marriages have lower RS

What is fraternal polyandry

Most common form in humans

• Woman marries brothers

• reduces impact on fitness because children he is helping to raise are his brother’s children (share some genetic material)

Polyandry example: Nyinba

• Nepal

• Fraternal polyandry where brothers set up a communal household with one woman

• Mixed industries - agriculture, herding, long-distance trade

• Paternity is tracked and considered important

Paternal uncertainty

• Men do not necessarily know who their children are

• Degree of paternity uncertainty varies by individuals, cultures, and circumstances

• From NHP model paternity uncertainty is predicted to influence paternal investment and investment of paternal family

Male investment in offspring will vary

• Are they his biological children

• Is their mother his current mate

What kind of men give the most support

If it is his child by his current mate (New Mexico)

What is the highest rating amount of care circumstance

Maternal grandmother (least is paternal grandfether)

Why is human infanticide different from NHP infanticide

Can be carried out by mother

Infanticide happens when

• Child is unlikely to survive

• Parents cannot care for child (related to social mating systems and rarely give up 1st born)

• Child not sired by the husband (similar to primates)

Human adoption

• seen in other animals but rare (more common in non-mammals)

• variable rates in humans but very common in some societies (normally adopted by kin)

• Idea of adopting non-kin considered odd in many societies

When parents are alive, give up children

• Reluctantly

• Because of lack of resources

• prefer wealthy relatives with no other children

• Maintain access to children and can reclaim them

  Asymmetries exist between resources given to biological and adopted children