In some cases, genetic variation in humans has performed a natural experiment for us. It's absolutely crucial to understand the potential impact of a proposed g

In some cases, genetic variation in humans has performed a natural experiment for us. It's absolutely crucial to understand the potential impact of a proposed genetic edit in the realm of messy reality. As an example, Ccr5 delta32 is present in a small fraction of Europeans, and noted for granting HIV immunity but potentially greater risk to West Nile virus. We don't know enough about all the real life consequences of Ccr5 delta32 at the moment, but natural experiments are a rich enough source of information to get us there, at least in theory.