Here’s a video of Louisians state Sen. Mike Walsworth questioning a science teacher about the teaching of evolution. He asked if there was an experiment that would prove the theory of evolution “without a shadow of a doubt.” The teacher mentions Richard Lenski’s brilliant experiment at MSU with E. coli, after which the senator asks if the bacteria evolved into a person.
This is a standard creationist tactic, of course, and it’s quite ridiculous. No, there isn’t a single experiment that can prove the evolution of man, which is what he is asking about, “without a shadow of a doubt.” Nor would any educated person expect there to be one. Evolution cannot be collapsed down into something so simple, it is actually a large collection of theories that form a larger model of the natural history of life on earth. There are lots of experiments that are done within each of those sub-theories, of course.
We know that the theory of evolution — the theory of common descent — is true because it is the only coherent explanation for a huge range of evidence over many different fields of science. It’s the only way to explain the patterns of appearance in the fossil record, the nested hierarchies that are present in both the fossils and in molecular sequences, and much more.