Episode Summary
Executive Summary: Michael Shermer interviews psychologist Steve Stewart-Williams about evolution, sexual selection, sex differences, crime, IQ, disgust, jealousy, and the limits of nature-versus-nurture arguments. The discussion emphasizes that many average sex differences are real but modest, overlap heavily, and should inform description without dictating prescription or rigid gender roles.
Main Topics: Natural selection and adaptation (Priority: 5/5): Stewart-Williams explains evolution as differential survival and reproduction, using lions' fangs and gazelles' speed to show how traits that aid reproductive success persist and create the appearance of design. Sexual selection and sex differences (Priority: 5/5): The conversation distinguishes sexual selection from survival-based selection and shows how differences in parental investment can produce male-female differences in coloration, aggression, mating behavior, and ornamentation. Controversies over average differences and greater male variability (Priority: 4/5): They discuss Larry Summers-style claims about greater male variability in cognitive traits, how such findings can be misread as inferiority, and why the public reacts more strongly to male-favoring than female-favoring results. Nature, nurture, and flexibility (Priority: 4/5): The speakers stress that biological influences do not imply immutability; culture can dampen aggression, extend altruism, and shape behavior even when evolved predispositions exist. Sex differences in sexuality, jealousy, and crime (Priority: 5/5): They examine larger sex differences in casual-sex interest, jealousy triggers, and criminal behavior, linking these to evolutionary pressures and to the male risk-taking/aggression profile, especially among young men. IQ, G, and multiple intelligences (Priority: 4/5): Stewart-Williams defends IQ and general intelligence (G) as robust, predictive constructs while rejecting the strong multiple-intelligences view as largely unsupported. Replication crisis and scientific standards (Priority: 3/5): The discussion ends with concern that psychology has improved after the replication crisis, but listeners should still wait for replication before embracing striking findings.
Key Arguments: Natural selection works by variation, inheritance, and differential reproductive success; traits that help survival or reproduction persist. Sexual selection is a subtype of natural selection that favors traits increasing mating success, often producing sex differences. Because females usually invest more in offspring, males often face greater variance in reproductive success, which can select for showy traits, aggression, and mating effort. Average sex differences are often heavily overlapping distributions, so anecdotes about exceptions do not refute group-level patterns. Public skepticism is often asymmetric: people are more bothered by male-favoring than female-favoring findings, partly because of historical concern for women. Biological explanations do not justify discrimination or prevent social change; culture can mitigate harmful evolved tendencies such as aggression. Male-favoring STEM gaps may reflect multiple causes, including some cognitive sex differences such as greater male variability, not only discrimination. Sex differences in casual-sex interest, jealousy, and criminality are robust and align with evolutionary pressures tied to paternity uncertainty, pair bonding, and risk-taking. IQ is one of psychology's most reliable and predictive constructs, and general intelligence (G) is more defensible than the idea of fully independent multiple intelligences. The replication crisis revealed that psychology needs stronger methods, and extraordinary claims should wait for independent replication.
Data Points: Podcast/book timing: A Billion Years of Sex Differences published in 2018; U.S. release mentioned as next year - Host introduces Stewart-Williams's new book and publication schedule. Greater male variability: Referenced as a documented phenomenon, especially in math ability - Discussion of Larry Summers and sex differences in STEM-related ability. Sex difference in sexual orientation target: D ≈ 3 - Stewart-Williams notes the primary target of sexual attraction as a very large psychological sex difference. Upper-body strength difference: Described as much closer to a categorical sex difference - Used to contrast physical versus psychological sex differences. Homicide perpetration: 90%+ perpetrated by men in every country on earth - Example of extreme male overrepresentation in violence. IQ score stability: High test-retest reliability - Stewart-Williams says IQ is consistently measured over time. IQ prediction: Predicts school performance, job performance, health, and longevity - Used to argue IQ has strong validity and practical relevance. Flynn effect: About 3 points per decade - Shermer notes long-term IQ score gains over the last century.
Pivotal Quotes: "The point of evolution, the point of life is to survive long enough to get your genes into the next generation." — Steve Stewart-Williams: Explaining the basic logic of natural selection and reproduction. "Nature, nurture, and noise." — Michael Shermer: Summarizing the idea that outcomes are shaped by genes, environment, and randomness. "We shouldn't be trying to wipe out sex differences, but we also shouldn't be amplifying sex differences." — Steve Stewart-Williams: His ethical middle-ground on how society should respond to evolved differences.
Implications: Listeners should treat sex differences as real but probabilistic, not destiny. Evolutionary psychology can explain patterns without excusing injustice, and scientific claims still need replication before driving policy or culture.