picking up on a tangent in that article:

<i>Two other perfect examples of "obvious-in-retrospect" theories are evolution and special relativity. Admittedly, I don't know if the ancient Greeks, sitting around in their togas, could have figured out that these theories were true. But certainly -- certainly! -- they could've figured out that they were possibly true: that they're powerful principles that would've at least been on God's whiteboard when She was brainstorming the world.</i>

To me, evolution is a perfect example of the need for practical knowledge. Darwinian and Lamarckian evolution are both absolutely reasonable theories; it's just that only one of them matches the world we live in.