Peter F. Hamilton thought this through in his novel Fallen Dragon.
The time machine used by the future humans would have to have been built in our past to make our past an available target. No matter whether humans develop the technology or not, getting back into human history before the invention would require use of a machine not built by humans.
Building one might help discovering a time machine built by a predecessor civilization. But you need the predecessors to have a time machine able to bring you into a time before humans invented the time machine.