They prove that people are imaginative. That is why H. Rudolphensis is rattling around in search of a home along with mesonychus, Lucy has turned back into a chimp, and Neanderthal is scratching his head wondering where his children went.
So now Lucy's a chimp? Was her knee found a mile from her head? Is Java Man just an orangutan? Is your subscription to Creation Ex Nihilo up to date? Anyway, you skipped a few. (Feel free to ignore any that were already known in 1859.)