Evolutionary Basis of Stratification

Kim Freire

Daniel Adkins

March 1, 2004

Presentation Outline

• Basics of evolutionary theory and sociobioloy

• Evolutionary basis for gendered minds

• A gendered perspective of cultural evolution

• Lopreato’s summary: sociological implications

Basics

Evolutionary terminology and concepts

Darwin’s Theory (1859)

1. Species reproduce faster than the corresponding resources can maintain.

2. Hence, populations must cope with resource scarcity.

3. Scarcity causes resource competition within or between populations; called “the struggle for existence.”

4. Some individuals are more successful than others in struggle, and therefore reproduce more often.

Darwin’s Theory (continued)5. Differential reproductive success is caused by variations

in genetic endowments.

6. Some variations are better adapted than others for competition; offspring are more likely among better adapted individuals/populations.

7. The preservation of favorable variations and elimination of unfavorable variation – natural selection – is due to differential reproduction.

8. Species transformation (diversification), via natural selection, leads to the creation of new species.

Evolution

• “Descent with modification”

• The process is uniform across species and ecological systems

• Transformation: change in gene frequencies (microevolution)

• Diversification: introduction of new genetic material (macroevolution)

Three Evolutionary Processes

• Natural Selection: preservation/elimination of favorable/unfavorable variation

• Heredity: the transmission of qualities from ancestor to descendent through genes

• Mutation: modification existing genetic material

Sociobiology

History and Basic Concepts

Modern History of Sociobiology

• Recent “field” of study, although many core concepts derive from the work of Malthus, Mendel and Darwin.

• A synthesis of ideas – rather than one theory - from multiple disciplines, particularly biology, anthropology, psychology and sociology.

• Many individual contributors; we’ll only name a few that represent biological, cultural, cognitive studies.

The Naturalist

• American biologist, Edward O. Wilson: wrote Sociobiology, published in 1975.

• Synthesized work of other scientists, such as Robert Trivers and Richard Dawkins (“The Selfish Gene”).

• Wilson also extracted ideas from his own work with ants, a member of the order Hymenoptera: “social insects.”

The Anthropologists

• Napoleon Chagnon’s studies of the Yamamano people (“The Fierce People”) correlated aggression with reproductive success.

• Anthropologists John Tooby and Leda Cosmides coined the term “evolutionary psychology” to neutralize conflict regarding biological basis of inequality.

The Cognitive Linguists

• Noam Chomsky and Steven Pinker weigh in from a cognitive-linguistic perspective of human nature.

• We know too little about core human capacities to make any final judgments about the validity of genetic vs. cultural theories of human behavior.

Basic Concepts of Sociobiological Theory

• Natural and sexual selection

• Phenotype/genotype

• Kinship

• Altruism/Selfishness

• Differential Parental Investment

• Fitness

• Adaptation

• Aggression

• Competition

Evolutionary Sex Differences

• All human societies have distinguished the sexes by their anatomy and behavior.

• Both socialization and biology affect patriarchal social arrangements.

• Key question: Is patriarchy the cause or effect of sex differences?

An evolutionary basis for gendered minds

Steven Pinker

and

Margo Wilson and Martin Daly

Theoretical Background

• Common theoretical underpinning to both of these readings:

Trivers (1972) Theory of Differential Parental Investment- If one gender is more invested (in terms of time, energy, and resources) in their offspring, this will lead to different selection pressures between the sexes.

Elaboration

• Human women must invest a minimum of 9 months pregnant, A man…30 minutes (a generous estimate).

• This difference will lead sexes to pursue very different reproductive strategies: men being less selective in choosing mates and females being highly selective.

• In this scenario women are the limiting factor in reproduction, thus men will tend to compete for their “affections”

Dominance-seeking monkey-brained men

• This intra-sexual competition between men leads to:

• Physical dimorphism in which males are larger than females. Size does matter… at least in dominating sexual competitors.

• Psychological dimorphism, in which males will be more prone to seek status, wealth, and power in efforts to enhance their reproductive attractiveness to females.

Nurturant females

• Among all animals in which females invest more calories and risk (than males) in each offspring (i.e.-pregnancy and nursing in the case of humans), females also tend to invest more in nurturing the offspring.

• Thus, among females, traits associated with being effective caretakers are often selected for.

Pinker’s Arguments

• Pinker’s intent is more general as he is seeking to establish that sexes have behavioral and physiological differences (in terms of population means), which are genetically based.

Pinker’s evidence• Pinker cites numerous “natural experiments” in which

children genetically of one gender were raised the other and eventually came to identify as their true gender.

• All human cultures share a sexual division of labor and the belief in different “natures”.

• Mitochondrial DNA (inherited from Mom) tends to be more diverse than Y chromosome DNA (from Dad)

• Androgens (e.g.-testosterone) have definitively been shown to associated with aggression, libido and self-confidence. They also have permanent, masculinizing effects on the developing brain.

Brain Differences

• There are differences in brain anatomy.

• Hence, there are differences in cognition, sensation and emotion.

• Male aggression is a mammalian adaptive trait related to fitness, which can be intensified or mitigated via socialization.

• Key question: To what extent are differences biologically vs. socially defined?

Feminism and Sociobiology

• Sociobiologists and “radical” feminists agree that:– men seek to control women

– patriarchal systems burgeon from males perceived need to control women

• However, these perspectives diverge in their rationale of domination: sexual selection vs. desire for power

• The most radical branch of feminism rejects the biological basis of sex/gender.

Wilson and Daly’s Argument

• Building on Trivers, the authors assert that males in competition for mates will tend to maximize their reproductive chances by seeking monopolize females.

• Humans reproduction is characterized by biparental care and internal fertilization. Which increases both the costs and likelihood of cuckoldry. Thus there are strong selective forces for ensuring one’s paternity of ones putative kids.

Evidence

• Swallows and Dunnocks

• Strict female monogamy not likely historically-testes size

• Harems

• Jealousy: normal reaction

• Differential care to genetic and step children

• Adultery: generally defined as a female act often legally punishable

A gendered perspective of cultural evolution

Rae Lesser Blumberg

Retreat to an Utopian Past

• This piece is somewhat dated; however, it raises interesting points about the female relationship to power and production in societies.

• Most of its points concern CULTURAL evolution (à la Lenski); thus we will only discuss a few salient points.

Blumberg: The pliability of gender relations

• Aside from its value as a historical document illustrating the social constructivist paradigm of the 70’s, this piece is valuable because it illustrates variation in female status across societal types.

• The implication being: even given genetically-based cognitive and behavioral sex differences, women’s roles in society are incredibly plastic depending on social structure.

Toward causality

• Blumberg attempted to locate the crucial causal mechanism influencing females’ status.

• She finds strong parallels between female empowerment and women’s relation to the means of production…

The Origin of Material Inequality

• Sharing: occurs mostly in absence of surplus

• Surplus: changes family structure; inheritance emerges

Environmental “Lushness”

• Abundant and reliable food sources – as well as other resources – facilitate more complex family structures.

• This family extension – beyond a nuclear unit - leads to less group sharing and increases sedentism, which leads to surplus.

• Inheritance systems emerge.

Cultivation

• Internal and external population pressures create a need for more food.

• Planting occurs.

• Women enlist their children to help grow food.

• Resource scarcity and population pressure leads to class stratification.

Sexual Stratification

• What is the degree of female power relative to males of her group?

• To what extent do females approach equal treatment and opportunities with the males of her group?

Women and Power

• Lenski’s power schema: property (i.e., economic), position, and force

• Females may have economic power in some groups, but males monopolize the latter two dimensions.

• Women’s relative economic power is the primary determinant of the relative equality of men vs. women in a group.

Female Economic Power

• Weber’s definition of power is the foundation.

• The extent of women’s control (relative to men’s) of production means and surplus distribution.

• Begins with labor production and can lead to land and capital.

Female Participation in Production

• Two key factors:1) Economic activity’s compatibility with child care responsibilities.2) The supply of male labor relative to demand

• Other “poker chips”:• Strategic indispensability• Kinship system• Men’s participation in child-rearing• Male superiority ideology• “Life Options”

In Summary: Female Paradigm

1) Power is most affected by control of production means.

2) Strategic indispensability is essential.

3) Kinship arrangement facilitate economic power and mitigate force.

4) Females are most oppressed when they have little or no economic power.

5) Females can translate relative economic power into greater life options.

Industrialization and Capitalism

• Commodification of land and labor

• Women increasingly participate in labor production and fertility rates decrease.

• Key question: How has industrialization/capitalism affected sexual stratification?

Lopreato’s Summary

• Current social stratification theories lack an evolutionary perspective.

• The failure of destratification efforts may be explained by evolutionary theory.

• Theory development requires a set of propositions to debate and empirically test.