Consider human evolution for starters: Homo erectus branched off from homo habilis some two million years ago (as best can be ascertained scientifically). At first, Habilis was still the big dog, and Erectus the newcomer… and it took half a million years before Habilis was gone and only Erectus was left. That's progress (albeit very slow progress) by a parallel path.

And, of course, we have the same sort of thing happening all through, ending (so far) with Cro-Magnon forming a parallel line to Neanderthal and eventually succeeding them. This is what nature does.

It's also what happens in human social development. Consider:

The Hebrews separated from the ancient civilizations1, survived as a parallel society, and delivered their base philosophy to the Western world after the fall of Rome. (And please believe me, while it's considered chic to lambaste Western civilization these days, those critics would go fetal upon arrival in an ancient civilization.)
Classical Greek civilization became what it did because of massively parallel paths… hundreds of them, scattered across the Greek archipelago. It was the multiple paths of the 8th, 7th, and 6th centuries BC that ultimately spawned the geometry, philosophy and literature that we know from the 5th century BC. Compare this to the anything-but-parallel Egyptian civilization that produced elite monuments and not much else.