Human Behavioral Biology

Masterclass in interdisciplinary science: Sapolsky shows why explaining any human behavior through a single 'bucket' (just genes, just hormones, or just environment) always fails.

Debunks naive 'for the good of the species' group selection and reconstructs social behavior from individual selection, Hamilton's rB > C rule, and Axelrod's Tit-for-Tat tournaments.

Shows how sexual dimorphism, parental investment asymmetry, infanticide dynamics, and genomic imprinting follow testable evolutionary predictions across primates.

Dismantles genetic determinism at the molecular level: how 95% non-coding regulatory DNA, alternative splicing, and environmental transcription triggers control gene expression.

This lecture continues the exploration of molecular genetics, focusing on domains of mutation and the molecular mechanisms of natural selection. Sapolsky integrates models of gradualism and punctuated equilibrium within an overarching framework of evolutionary development.

Explains why heritability is a variance statistic about environments—not a measure of how 'genetic' a trait is—and exposes prenatal confounders in classic twin studies.

Robert Sapolsky explicates the mechanisms of kin recognition across species, detailing innate recognition through protein signatures and olfactory cues, and learned recognition via cognitive and sensory processes. The lecture examines the evolutionary implications of relatedness in reproductive strategies and social behaviors.

This lecture provides an introduction to ethology, examining animal behavior in natural contexts. Sapolsky discusses fixed action patterns, informational stimuli, and the interplay between genetics and environment in shaping complex behaviors, including an overview of neuroethological principles.

This lecture dissects the intricate communication systems within neurobiology, examining the limbic system's role in personality and abnormal behavior, and exploring individual variation and imprinting.

Professor Sapolsky elucidates the limbic system's pivotal role as the emotional center of the nervous system, detailing its influence on decision-making and cortical connections.

This session investigates the proximal and distal motivations behind human reproduction, including discussions on orgasm, fertility, non-reproductive sex, and the interplay of hormones and cerebral functions.

This lecture, the second in a series, traces the evolutionary trajectory of human sexual behavior, analyzing how complex adaptive mechanisms have shaped its current intricate forms.

The lecture concludes the discussion on sexual behavior by examining attractiveness cues across species, then pivots to the evolutionary and cultural development of human aggression.

Continuing the exploration of human aggression, this session delves into the neurobiological underpinnings of various emotions, elucidating the complex brain mechanisms that drive these behaviors.

This lecture continues the neurobiological analysis of human aggression, exploring correlations with neurotransmitter levels, genetic variance, societal factors, and the role of alcohol.

The final part of the aggression series synthesizes the roles of hormones and evolution in shaping aggressive and violent human interactions, providing a comprehensive view of their behavioral impact.

This challenging lecture critically examines the principles of reductionism in science, discussing how breaking down complex systems into their component parts aids in understanding, with reference to assigned readings.

Professor Sapolsky introduces concepts of emergence and complexity, illustrating how minor initial differences can lead to profound systemic effects through fractal magnification across various natural systems.