For decades, the search for the last common ancestor of all living apes focused on East Africa. The logic was straightforward: the richest fossil sites for later hominids — Olduvai, Turkana, Hadar — are in East Africa. The earliest known members of our genus were found there. So the ancestor must be there too.
Masripithecus, a fossil ape from northern Egypt dating to 17-18 million years ago, may be the closest known relative to the lineage that produced all living apes — gibbons, orangutans, gorillas, chimpanzees, humans. It wasn't found in East Africa. It was found in the Sahara.
The search area was defined by the assumption: because later hominids lived in East Africa, early hominoids must have originated there. But origin and diversification can happen in different places. A lineage can begin in one region and radiate to another. The ancestor doesn't have to live where its descendants flourish.
This is a general pattern in any search: the map of where to look is drawn by the results already found, not by the evidence for where to look. Early finds create a concentration of fieldwork, which creates more finds, which creates more fieldwork — a positive feedback loop that systematically under-samples everywhere else. Northern Africa wasn't neglected because the evidence was absent. It was neglected because East African evidence was present, and presence attracts more attention than absence attracts curiosity.
The correction is not geographic. It's epistemological. The question was never “where in East Africa is the ancestor?” It was “why are we only looking in East Africa?” — and the answer was: because that's where we already found things. The search was biased by its own prior success.