Here is the hypothetical evidence that he believes would falsify the theory: “If we found an organism that clearly breaks out of the evolutionary tree we know. Say - a 5 legged creature, or an animal without DNA, or an animal that has a DNA that doesn’t have any common parts with the rest of the life on earth.”
Such a find would certainly be compelling, but I would first consider that the outlier was created artificially or evolved in isolation of all other known life before throwing out evolutionary theory. As unlikely as either of these sound, they would be more reasonable explanations. To show evolution is false, each line of evidence needs to be overturned. Each aspect of the theory needs to be falsified. Evolution isn’t too big to fail, but it’s certainly too big to die of a single counter-point.*
(*Unless, of course, that counter-point was that all known evidence was found to be lies planted by the Great Deceiver. Positing the devil as a way to reject evolution is one of the more honest and internally consistent methods--if only it wasn’t based entirely on mythology.)
Back to reality...or at least hypothetical reality--even if such a find could impact evolution as a whole, it would revise the theory, maybe falsifying parts, before it would falsify the whole shabang. This happened before with the theory of gravity. Isaac Newton understood gravity in a manner that worked to explain all gravitational movement...at first. It didn’t quite work with the solar orbit of Mercury, much like current evolutionary theory wouldn’t work for the aforementioned hypothetical creature. It wasn’t until Einstein hashed out relativity that a new understanding of gravity could account for Mercury. If we one day discover gravitons or something, we might have to adjust gravitational theory further. Edits aside, I can think of no natural evidence regarding either evolution or gravity that could falsify all previous findings that work perfectly well with what we have. Natural selection happens. Mutations occur. Heritability is a thing. If you find a glaring example of uncommon decent, let me know. It could modify evolutionary theory, but smart money says it's an alien.
