Aspects of human beings that are widely present in people all over the world, and are therefore likely resistant to effective removal using known practical tools, is generally considered reasonable (but not incontrovertible) evidence for biological inclination. It is not necessary to have linked this to a particular gene, and doesn't cease to be "biological" if it involves gene-environment interactions. It was correct to say that most plants were biologically inclined to use the sun's energy before photosynthesis and DNA were understood.