We've walked you through Dougal Dixon's speculative evolution book on the dinosaurs that might have been. In his follow up, Man After Man, he's trained his cruel eye upon mankind, and brought to life a horror show of humanoid successors to homo sapiens.
The central premise of the totally gonzo book is this: in this particular future hellscape, man will have dipped into his own DNA to genetically engineer humanoid horrors that perform specialized labor. These big dumb beasts outlive us when humans trash the environment, and inherit the Earth. (Also, we evolve telepathy, so hooray?) Here's how some of our creations turn out after 5 million years or so. Enjoy!
Source: MONSTER BRAINS