With the phrase "stone age hunters" the author compares the behaviors he witnessed in the roads of Tennessee and Ohio, to those of stone age hunters, meaning he considers those behaviors as underdeveloped and archaic, especially implying a standardized behavior in their sexual patterns.
"Genderless cities" is used to express cities where gender is not consider an important factor of judgment this implies also sexual orientation is also seen without judgment and the writer implies this as a form of development in cities of the future.
I believe he means that people without many resources(stone age hunters) like homeless people or unfortunate people. Genderless cities are places where gay rights are not frown upon and people are not judged because of their gender or their sexual orientation. I hope this helped :)<span />
