Nature and Nurture: Reconciling Evolutionary

Psychology and Cultural Anthropology, part II

In the West, because you fall in love

and are ready for marriage.

Why do people get married?

A synthesis of evolutionary psychology and cultural

anthropology gives a somewhat different answer:

People get married because a desire for long-term

relationships increased the inclusive fitness of our

ancient ancestors, with the form of marriage subject

to cultural influences.

During the period of human evolution,

babies with fathers around were more likely

to survive.

The Nayar in southern India: a society without marriage?

Regardless of the answer, beware of letting a single case

undermine any attempt to generalize.

Marriage is universal or near-universal,

but its form varies across societies.

Forms of Marriage:

Of all societies that have been studied,

82% were polygynous,

17% monogamous, and

<1% polyandrous.

monogamy is where you can be married to only one person

polygamy is the general term for multiple marriages

polygyny is where men can have more than one wife

polyandry is where women can have more than one husband

In polygynous societies, only high-status

men have multiple wives. Thus, most

societies are polygynous, but most

marriages—even in polygnous societies—are

monogamous.

The handful of polyandrous societies on

record existed in environments with

scarce resources. Two brothers often

share the same wife, which keeps the

birth rate low.

Across societies, marrying for love is rare.

In most societies, marriages are arranged,

often with input from the bride and groom.

In summary, marriage shows both evolutionary and cultural

influences.

Arranged marriages are usually more stable

than Western love marriages.

Is a mother’s love for her baby universal?

Our cultural norm (for example, in movies) presumes

instant bonding between a mother and her baby.

Nancy Scheper-Hughes,

Death Without Weeping

Fieldwork in a shantytown in one of the poorest

parts of Brazil.

The birthrate in the shanty averaged

9.5 per woman.

On average,

1.5 were stillborn

3.5 died young, usually before 6 months

4.5 reached adulthood

The mothers did not take extra measures to save weak

or sick infants (“passive euthanasia”). The mothers did not

cry or mourn when infants died.

Scheper-Hughes: maternal love is not universal.

Historians of the Middle Ages have found a similar pattern

during times and places of high mortality.

So is maternal love a cultural phenomenon devoid of

evolutionary influence?

Smith: No, evolution has a strong influence too.

Which evolutionary strategy would pass

more of a mother’s genes into future

generations?

1. As a legacy of evolution, mothers have an innate desire

to shower love and resources on every child from the

moment of birth.

OR

2. As a legacy of evolution, mothers have a flexible desire

that grows over time according to a child’s likelihood of

surviving to adulthood.

The shantytown in Brazil and the experiences of the

Middle Ages show strategy #2 at work.

Even in our own society, instant bonding is a myth.

New mothers sometimes don’t feel the

bond and instead suffer from post-partum

depression.

Most societies on record have practiced

infanticide through child sacrifice, direct

killing, or exposing an infant to the

elements.

Can the logic of strategy #2 give us insights into why and

when people practice infanticide?

In a study of 60 societies, the following reasons were most

common for infanticide:

deformity or illness in the baby

multiple births (usually twins)

timing (too soon after a previous birth)

economic hardship

absence of the father

These are all consistent with strategy #2. Either the

infant is unlikely to survive and reproduce, or the mother

cannot support it.