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That era in the fossil record IS indeed sparse, but not unexpectedly so. Primate populations are typically very small (until Homo sapiens came along). For example, we do not know nearly as much as we'd like about the evolutionary divergence of ANY of the great apes, for exactly the same reasons.
1. Homo sapiens have always been in numbers of millions and congregated together in large numbers. -Not true 2. Fossil discovery, extraction and analysis is easy. -Also not true. There is another thread going on right now about whether or not the discovery of extraterrestrial life (aliens) would impact religious belief? I actually think that finding more fully intact fossils from this era would do more to shake up belief. I wish them well in Ethiopia.