"Culture tends to argue that it only prohibits what is "unnatural." But from a biological perspective, nothing is unnatural. Something that goes against the laws of nature simply cannot exist. In reality our concepts of natural and unnatural do not come from biology but from Christian theology.

Christian theologians argue that God created each organ for a specific purpose. If we use it for that purpose it is natural, if we don't do it differently it is unnatural.

However, evolution does not have a purpose, organs evolve to perform a specific function, but once they exist they can be adapted for other uses.

An example is the mouth, the mouth appeared because primitive multicellular organisms needed to incorporate nutrients into the body, today we still use the mouth for this purpose but we also use it for many others, like playing instruments. Is this unnatural just because our ancestors didn't do these things with their mouths? No".
Is he right?