I hope this is appropriate. Heritability has come up a few times on HN, and there was usually a fair amount of discussion about what the numbers really mean. S

I hope this is appropriate. Heritability has come up a few times on HN, and there was usually a fair amount of discussion about what the numbers really mean. See for example: * "Heredity beyond the gene" https://news.ycombinator.com/item?id=16543703 https://news.ycombinator.com/item?id=16543703 in 2018 * "The heritability of self-control: A meta-analysis" https://news.ycombinator.com/item?id=21638463 https://news.ycombinator.com/item?id=21638463 in 2019 * "Lifetime earnings are 40-50% heritable" https://news.ycombinator.com/item?id=21408139 https://news.ycombinator.com/item?id=21408139 So I thought that it might be useful to have a post that really nails down what exactly the definition is. It has some strange properties that few people seem to be aware of: For example (as alluded to in the title) it's possible for heritability to be higher than 100% if environmental effects are negatively correlated with genetic effects.