Scott Alexander responds to comments and criticism on his earlier post about 'Missing Heritability', discussing issues like gene-environment interactions, sequencing technology limitations, and the use of polygenic scores across ancestry groups. Longer summary

This post compiles and responds to notable comments on Scott's earlier post about 'Missing Heritability'. The post is structured in four sections, starting with responses from experts named in the original post, particularly Sasha Gusev who critiques the treatment of gene-environment interactions and cross-population polygenic scores. The second section features detailed technical comments from knowledgeable readers about topics like genetic interactions and sequencing technology limitations. The third section addresses specific corrections to the original post, while the final section covers various other interesting comments and discussions. Throughout, Scott engages with the criticisms and new perspectives while maintaining his original position on most key points. Shorter summary

Scott explores the 'missing heritability' problem in genetics, where twin studies show traits like IQ and educational attainment are highly heritable but newer genomic methods find much lower heritability, analyzing various potential explanations for this discrepancy. Longer summary

The post examines the 'missing heritability' problem in genetics, where twin studies consistently show behavioral traits like IQ and educational attainment are substantially heritable (around 40-60%), while newer genomic methods find much lower heritability (around 15-20%). Scott reviews the history of behavioral genetics research, explains various study methodologies and their potential biases, and analyzes different hypotheses for this discrepancy. He examines whether twin studies might be flawed, whether newer methods might be missing important genetic effects, and whether educational attainment might be an unusually problematic trait to study. While acknowledging remaining mysteries, he tentatively concludes that twin studies are probably largely correct and that newer methods may be missing rare variants and genetic interactions. Shorter summary

Scott Alexander argues that schizophrenia should be described as predominantly genetic, addressing counterarguments and emphasizing the importance of this perspective for prevention strategies. Longer summary

Scott Alexander argues that it's fair and accurate to describe schizophrenia as predominantly genetic. He responds to various arguments against this characterization, comparing the situation to how we discuss smoking causing lung cancer. Scott emphasizes that while environmental factors play a role, genetic factors account for the majority of variance in schizophrenia risk. He argues that acknowledging the genetic nature of schizophrenia is important for developing effective prevention strategies, such as polygenic screening, rather than focusing solely on hard-to-control environmental factors. Shorter summary

Scott Alexander uses simulations to explain why seemingly counterintuitive arguments against the genetic basis of schizophrenia are misleading. Longer summary

Scott Alexander discusses two seemingly counterintuitive arguments against the genetic basis of schizophrenia and explains why they're not as compelling as they might appear. He uses a simplified simulation to demonstrate how a highly heritable disorder can have low twin concordance rates and why eliminating affected individuals doesn't significantly reduce prevalence in the next generation. The post aims to clarify common misunderstandings about polygenic disorders and their inheritance patterns. Shorter summary

Scott Alexander discusses his confusion about polygenic inheritance, mutational load, and the paternal age effect in genetics, seeking explanations from readers. Longer summary

Scott Alexander expresses his confusion about several aspects of genetics, particularly regarding polygenic inheritance and intelligence. He starts by discussing the low contributions of individual SNPs to intelligence despite high heritability, questioning how this reconciles with the observed variation in human intelligence. He then explores the concept of mutational load and its implications, as well as the paternal age effect. Throughout the post, Scott presents various scenarios and analogies to illustrate his points of confusion, inviting readers to help explain these genetic concepts. Shorter summary