The Ground Plan of Evolution

Abstract

I remember reading a horror story in my youth entitled “The Fly,” later made into a successful movie. It is the story of a man who invents a method for the instantaneous transfer of matter from one place to another. He became so confident in its operation that he started transferring himself across his laboratory from the transmitter to the receiver. Unfortunately, one day there happened to be a fly with him in the transmitter chamber. When they arrived at the receiver, they had become partially mixed up! The man had the head of the fly instead of his own head, and a fly’s leg in place of one arm. The fly had received the human head and arm in place of its own organs. The story ploughs on to inevitable disaster. But it makes us wonder whether such a substitution could really happen. In other words, are there equivalent parts in the bodies of flies and people? Is the fly’s head like the human head, and is the fly’s leg like the human arm? Actually, flies have six legs, and the three pairs are not the same, so if this disaster had happened for real, which of the fly’s legs would have been substituted for the human arm? Such questions may seem fanciful, but millions of dollars of grant money are being expended at this very moment in trying to answer them.