Good reading, it'll open your mind a bit, but take it with a big grain of salt.
Von D, in my opinion, didn't give early man the benefit of the doubt (i.e. Egyptians couldn't have figured out surveying! ...because the Pyramids are too accurate! etc...) There's some evidence now, I think, that the latter Greek/Egyptians learned the water level tool and basic algebra, from 'the ancients'. Which weren't ET's, just their GGGGGGGGGGG grandparents. Humankind has forgotten many hard learned lessons throughout our history.
Keep in mind, when 'Chariots' was written, people were only just getting used to the idea that the 'Vikings' beat Columbus to the 'New World' (by almost 500 years).