>There are, and has been, hundreds of different cultures. Some have similarities, some are profoundly different.
These cultures didn't emerge from a vacuum completely in isolation from one another. Their similarities and commonalities are what form the basis for these categories, broad though they may be.
There are, and has been, hundreds of different cultures. Some have similarities, some are profoundly different.
(I'm not trying to dismiss your whole point: I agree with everything else you wrote)