> A Twin study is hardly comparing Sierra Leone with Japan, or the Netherlands with North Korea. Extremes like iodine deficiency, disease, or fetal alcohol synd

> A Twin study is hardly comparing Sierra Leone with Japan, or the Netherlands with North Korea. Extremes like iodine deficiency, disease, or fetal alcohol syndrome are similarly excluded. Sure. To take this line of reasoning to its conclusion, an environment that has no oxygen or is otherwise uninhabitable, would prevent any human from living or having any mental abilities whatsoever. In this sense, environmental influences would completely dominate genetics. Similarly, changing 50% of a human's DNA would have them live life as a stalk of wheat. What's your point?