I'm being serious, I'm sure thats what happened here. I doubt the guy is just knowingly grifting for book sales, he probably just held onto this idea as a pet theory during his career and sort of compartmentalized it from his primary academic work. edit: considering he was an interpretivist cultural anthropologist, that appears to be the case, its not like he spent a career studying hominid fossils.

That said this is cryptozoology stuff is (relatively) harmless compared to the more common emeritus meteorologist/physicist that uses his credentials to explain to those primed to listen why anthropogenic climate change is bullshit