How might vestigial organs be a clue to an animals evolutionary history?

The standard definition of ?vestigial? is an organ that once was useful in an animal?s evolutionary past, but that now is useless or very close to useless. Over 100 were identified and touted as proof of evolution. Since then functions have been found for all those vestigal organs so the proof of evolution disappeared. Undeterred evolutionists simply changed the definition of vestigal to any part of an organism that has diminished in size during its evolution.

This is but one example of why evolution is unfalsifiable and hence not science.

They're traits that are vital in other animals, but don't have very much use in humans.  That's not the same as saying that they have NO use, just that they're not as vital in humans as in other animals.  The appendix is one example.  There's some evidence that it plays a role in maintaining the bacteria in the gut, but it isn't required for digesting food.  In herbivores, though, it's very highly developed, and plays a crucial part in digesting plant matter - if you removed a rabbit's appendix, they would have a hard time getting enough nutrients to survive.

Since vestigial organs don't serve an important function, it's less likely that they would have evolved independently, through convergent evolution.  The appendix appears to have evolved independently in mammals and marsupials.  However, it's unlikely that the same structure would have evolved independently in, say, rabbits, where it greatly enhances their ability to digest food, and in humans, where it provides a slightly useful but non-critical function.

It's not unfalsifiable, though.  All you would have to do is show that a vestigial organ didn't share the same basic genetics or developmental stages, and it would lose its status as vestigial.  If you could show that the human appendix evolved independently from those of other mammals (as in the case of mammals and marsupials), it would no longer be considered vestigial.  As with pretty much everything else on creation.com, that claim is complete baloney.