Generation
A generation denotes, in biological terms, the cohort of offspring produced contemporaneously by a parental set, with the average human generation interval—measured as the age of parents at the birth of their children—estimated at 26.9 years across the past 250,000 years from whole-genome sequence analyses of diverse populations.[1] This interval reflects empirical patterns in reproductive timing, varying by sex (shorter for females at approximately 23.2 years) and stable over deep time despite cultural shifts.[1] In familial contexts, generations delineate vertical kinship structures, tracing descent lines across multiple intervals, as evidenced in genealogical records where survivor bias underscores the continuity from ancestors to descendants. Sociologically, the concept extends to generational cohorts, groups sharing proximate birth years and thus positioned similarly within historical processes, a framework articulated by Karl Mannheim to explain how youth exposure to rapid social change can foster collective orientations distinct from adjacent age groups.[2] However, while such cohorts may encounter shared events influencing attitudes or behaviors, rigorous empirical scrutiny reveals scant evidence for enduring, generation-specific traits independent of age-period confounding; differences attributed to "generations" like Baby Boomers or Millennials often dissolve under longitudinal analysis, with lifecycle stages and individual variability proving more causal.[3][4] This critique highlights the non-falsifiable nature of popular generational theories, which prioritize narrative over testable predictions, leading to overgeneralizations in policy, marketing, and media despite biological generations remaining a precise, data-grounded metric.[4]