I am always on the lookout for better ways to express the evidence for evolution. One common doubt is that we have never actually observed one species giving rise to a new species, so how do we know that speciation occurs in nature?
The claim makes me think of the trial where a man was charged with biting off another man’s ear in a bar fight. (Incredibly, Mike Tyson was not involved.) An eyewitness to the fracas took the stand. The defense attorney asked, “Did you actually see with your own eyes my client bite off the ear in question?” The witness said, “No.” The attorney pounced: “So how can you be so sure that the defendant actually bit off the ear?” To which the witness replied, “I saw him spit it out.” We have the fossils, the intermediate forms, the comparative anatomy, the genomic homologies—we’ve seen what evolution spits out.