“Tongue-rolling is genetic.”
Mostly false. Not enough data, and probably a generalisation of the term ‘genetic’.
A famous 1940 paper claimed tongue rolling was at least partially genetic. Another famous 1975 paper refuted this. Currently, there is not enough data to come to a solid conclusion, but most of the evidence points out that this trait arises from specific environmental influences that affect the individual.
See other: Mythconceptions?