They do. They kept evolving too. Its like Saying "if we came from monkeys, why are there still monkeys". Well we didnt come from todays monkeys. We came from a common ancestor, which we have fossils of, and separated down multiple paths, each one specializing and changing differently. Today's monkey is just as different from its ancestor as we are. And as for why the ancestor wouldnt be around today as it was then- is going to be breeding and adaptation, its impossible to stop mutating and evolving, so they just kept changing the way we did. Keep in mind, we are the acestor of something that doesnt even exist yet. In all likelyhood if we ever colonize other planets, we will divide and become multiple species of human, based upon closed breeding options and environmental mutations.