It's based on fear of change -- that something bad might be in newer foods. Taking this advice to heart would mean limiting what we eat to just a few well-known

It's based on fear of change -- that something bad might be in newer foods. Taking this advice to heart would mean limiting what we eat to just a few well-known, well-tested foods. And yet the common best-practice nutritional advice is to eat a wide variety of foods. At the same time we know of plenty of natural raw foods, and even some simple cooking processes, that are harmful. I'd actually advocate for both practices. It's how animals survive best: some members of a species are risk takers and others are cautious, so that one or the other is likely to survive any change in environment.