You can neither manipulate nor naturally observe the full range of possible cultural variation, though. And this problem will in fact inflate the additive gene

You can neither manipulate nor naturally observe the full range of possible cultural variation, though. And this problem will in fact inflate the additive genetic estimates. Ie. if we only observed plants in 21% oxygen, or never modified diets in phenylketonuria, we'd miss something important (in these simple cases, we knew it from other sources, but it's rarely this easy).