Cremo's "research" is deeply flawed, relying upon resources from the late 19th and early 20th centuries, the book ignores newer data that contradicts his claims. Disregarding all the current research on human evolution, Cremo barrels on making comical claim after comical claim, never providing any solid data to back up his fantasy land.
A nice detailed review of the book can be found here:
Despite all this hard work, I think the book falls short of a scientific work primarily (but not entirely) because (1) its arguments abandon the testing of simpler hypothesis before the more complex and sensationalistic ones, and (2) the use of so many outdated sources is inadequate for a book that seeks to overturn the well-established paradigm of human evolution -- scholars must not work in isolation, especially today, when multi-disciplinary approaches are needed to remain on the cutting edge of knowledge. However, for researchers studying the growth, folklore, and rhetoric of pseudo-science, the book is useful as ‘field’ data.
I hesitate in judging the book to be utterly worthless from a scientific standpoint -- various specialists need to compare notes on the book -- but if worthy ideas exist in Forbidden Archaeology , they are hidden under a mass of undisciplined details, lack of critical contextual information, leaps of logic, and special pleading.
"Forbidden Archaeology" makes a lot of claims based upon inaccurate data. The sheer volume of bad data gives it a sheen of believability, mainly because it would take so much time to examine each piece of flawed information. In the end, Cremo doesn't support his claims with reliable source material.
The question at hand is this:
Is Cremo an incompetent researcher with a poor grasp upon reality, or an outright fraud, intent upon deceiving people to sell books?