Complex sentence: Historian Milo Milton Quaife, however, regarded Kinzie's account of Point duSable as "largely fictitious and wholly unauthenticated", later putting forward a theory that he was of African and French-Canadian origin.
Split into simpler sentences: Historian Milo Milton Quaife, however, regarded Kinzie's account of Point du Sable as "largely fictitious and wholly unauthenticated". Quaife later put forward a theory that he was of African and French-Canadian origin.