Human evolution in a special place is a model that scientists try to avoid. It’s like thinking that humans came from another planet.
But all the evidence points to that. Humans have weaker muscle fiber than any ape or monkey, and are born with blubber instead of muscle. Humans cannot run fast, swim fast, or climb well. They have no fur for defense against cold, sun, or insects, and no sharp teeth or claws for defense against predators.
Without their big brains, fire, tools, water-containers, and weapons, humans could not survive today anywhere in mainland Africa. They would only have a chance on a warm isolated island where there happens to be plenty of food and fresh water, and no crocodiles, leopards, wolves, or other predators. This is actually a common setting for remarkable evolution, and is known as 'the Island Syndrome'. Galapagos islands provide good examples, and there are many more.
Bioko reminds scientists of the Garden of Eden. For the past century, scientists have been trying to get away from that model — of humans being specially created in a specific place and time. Scientists never want to go back to long-rejected models. But if compelling DNA evidence comes along, we will have no choice.
Try to think of Bioko as a Galapagos model, rather than a Garden of Eden model.