This general theory of ancient civilization teaching mankind math and science and being wiped out by the flood (for the most part) is consistent with Mesopotamian/Sumerian and ancient Hebrew literature...and probably with the mythologies of plenty of other ancient cultures.
You are exactly right and he is also questioning the accuracy of carbon dating with is alone enough to explode the heads of the atheists.
I heard that Graham Hancock originally set out to prove something more like “aliens visited”, but as he investigated more and more began to prove to himself the biblical story in the book of Genesis might be real after all.
…J. Harlen Bretz's theory is that Washington State's “Channeled Scablands” were formed by repeated cataclysmic floods over only about 2,000 years, rather than through the millions of years of erosion that had been previously assumed.The lake was the result of an ice dam on the Clark Fork caused by the southern encroachment of a finger of the Cordilleran ice sheet into the Idaho Panhandle (at the present day location of Clark Fork, Idaho, at the east end of Lake Pend Oreille). The height of the ice dam typically approached 2,000 ft., flooding the valleys of western Montana approximately 200 miles eastward. It was the largest ice-dammed lake known to have occurred. (Wikipedia)
I think you are on to something and I think those civilizations were here and were destroyed in the time frame between Genesis 1:1 and 1:2. What happened in that era could have been apocalyptical for Earth and the solar system in general.