Welcome to EvC MauriceAWilliams, hope you enjoy your stay.
MauriceAWilliams writes:
I find it hard to imagine that human beings with the language skills and inventiveness to make tools, clothing, etc. that we all think humans possess could have given rise to a life form with vastly inferior communication skills and inventiveness
It's not too hard to imagine if one conciders that all the language and skills you mention are very recent additions: the proposed time in which diagonograde body plan reamerged is easily long enough (10 to 25 mya) for a couple of 'reverts'.
As to the first uprights being homo sapiens sapiens at this time I would doubt. As I understand it modern humans are first encounterd in the fossil record at 130,000 BCE.
All this is said without having read the book so I may have misunderstood some of the arguement.