Evolution Explains Polygenic Structure

Third in the Torrey schizophrenia-genetics series. Answers two of Torrey's objections (no large-effect genes found; evolution should have purged risk genes) with one mechanism, via Michael Roe's comment: large-effect deleterious variants ARE selected out, so what remains must be massively polygenic small-effect variants held at mutation-selection balance. Generalizes: any fitness-relevant trait (intelligence, schizophrenia) is necessarily polygenic. Then canvasses why small-effect risk variants persist (evolution hasn't finished; legible counter-advantage like creativity; scattered per-gene counter-advantages), favoring the 'evolutionary mistakes, not yet purged' answer, with the ancient-genome trend as support and a clean embryo-selection footnote.

Quality 66 · Strong. Strong (low): a genuinely clarifying, well-reasoned piece of population genetics that dissolves two objections at once, but short and incremental within an ongoing series rather than standalone-major.

Claude’s paradigm shift 48 · Moderate. Moderate: the 'fitness-relevant therefore necessarily polygenic' framing is a crisp synthesis, though it restates standard mutation-selection-balance theory.

Real-world impact 2 · Minor. Minor/within-blog: bears on embryo selection but is an explanatory argument with no direct material footprint.