It probably wouldn't take a billion years. The last common ancestor of humans and orcas seems to have been about 95 million years ago. For reference, a billion

It probably wouldn't take a billion years. The last common ancestor of humans and orcas seems to have been about 95 million years ago. For reference, a billion years ago, there were no animals or plants yet. Given that, maybe there are a lot of species that really weren't too far off from human level intellligence, but we just got there first?