Sexual Dimorphism
the male/female face split is real, but it's a dial, not your destiny
Grounded in the research on Wikipedia: Sexual dimorphism; facial-masculinity research (Penton-Voak, Perrett)
what it is
sexual dimorphism is just the average difference in form between males and females of a species. in faces it means men's faces trend bigger jaws, heavier brows, longer lower-thirds; women's trend smoother, rounder, bigger eyes relative to face. emphasis on average. it's a population trend with massive overlap, not two clean boxes everyone fits in.
the science
testosterone and estrogen sculpt this at puberty. the 'good genes' idea that masculine faces signal fitness traces to evolutionary psych work in the 90s, but it cracked fast. Penton-Voak and Perrett (1999) found women's preferences for masculine male faces shift across the menstrual cycle and toward feminine for long-term partners. translation: 'more masculine = more attractive' was never the clean law looksmaxxing forums sell.