It’s all thanks to a gene called CD33 that evolved to fight gonorrhea, but the Neanderthals and Denisovans weren’t so lucky. — We, humans, are shrouded in mysteries. For as much as we’ve learned about ourselves over the last few centuries, we have no idea how much we still don’t know. We don’t know why, for example, out of the dozens of Human species we’ve discovered, we’re the only ones to have…