The fact that you are descended from your father doesn't mean he's dead.
When a new species arises, it is can be that the parent species gradually turned into the child species. But equally, the child species could have forked off, leaving the parent species intact and unchanged. Perhaps the child species arose in some isolated group, leaving the main population unaffected.
The theory is not that humans are descended from chimpanzees, or from gorillas, or bonobos, or orangutans. The theory is that all of these are descended from a common ancestor.