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Nobody credible has ever seriously proposed doing this sort of ridiculous analysis of variance. It seems clear that not every aspect of the environment matters. (The number of snowflakes which hit my face during February was either odd or even, but it's hard to see how that could change my present weight.) Similarly, not every genetic distinction makes a difference to the trait. If we could somehow identify relevant distinctions, and group together organisms with relevantly-identical genotypes, we'd be doing something much more reasonable. The true heritability of the trait is defined to be the ratio between the variance associated with genetic differences and the total variance in the trait. - bactra.org