WASHINGTON (Reuters) - A gene that separates humans from the apes and all other animals seems to have disappeared from humans up to three million years ago, just before they first stood upright, researchers said on Monday. Most animals have the gene but people do not -- and it may be somehow involved in the expansion of the brain, the international team of researchers said. The gene controls production of a sialic acid -- a kind of sugar -- called Neu5Gc, the researchers write in an advance online issue of the Proceedings of the National Academy of Sciences ( news...