Genetics and Society

Everything’s Heritable

• First Law. All human behavioral traits are heritable

• Second Law. The effect of being raised in the same family is smaller than the effect of genes

• Third Law. A substantial portion of the variation in complex human behavioral traits is not accounted for by the (additive) effects of genes or families.

Genetic Architecture

• Fourth Law: Genetic variants that are common in a population have very small individual effects on behavioral traits

• Not always like this in other species

• Can be different in subpopulations

• Strong selection can change architecture

The twin studies are all right

• According to GCAT

Selection

• Every society selects for something

• Usually unintended

Breeder’s Equation

• R = h2S

• R = response

• h2 = narrow-sense heritability

• S = selection differential

Selection can be fast or slow

• Interesting changes can happen in less than 1000 years

• Maximum time available for human differentiation, ~100,000 years

Dan Freedman’s babies

• Behavioral differences at birth

Populations, Classes, Jobs

• Selection changes populations

• Classes change by selection and differential recruitment

• Jobs, differential recruitment

Distributions

• Modest differences in the mean imply big differences at the extremes

Genetic Isolation

• Geographic Separation

• Endogamy

Epigenetic Inheritance

• Trendy

• Rare

• Hard to imagine adaptive mechanism

• fuhgeddaboudit

Human Capital Formation

• Usual Model: Parents invest in human capital

• Fewer kids is better

• Not true for genetic contribution