I disagreed with David's views on Tiwanaku, ditto on what he said about construction of the Inca sites over the border in Peru, and that set the scene for me for the rest of the interview unfortunately - i.e. he had a bit of a credibility issue. Having lived for years down the road in La Paz I've had the chance to visit the above sites a fair number of times, and while they're undoubtedly impressive (and most certainly mysterious in Tiwanaku's ancient case), for me there's nothing there which couldn't have been built using local materials through a combination of clever engineering for its day, craftsmanship, political will to get the job done and plenty of brute force. I felt that David was very selective in citing evidence (and sometimes he didn't bother at all!). For example, many of the larger slabs at Tiwanaku have grooves for fitting ropes to move them into place. The Tiwanaku pyramid itself, while large in area, was in reality pretty flat, more of a platform than something you'd find in Egypt or Central America, plus the majority of the complex has been constructed from much smaller-sized building materials than monolithic slabs, as is immediately evident once you have a wander around. The latter is also true of Ollantaytambo and Machu Picchu, for example, and the Incas' use of hefty ropes to assemble places like Sacsayhuaman is documented by the Spanish conquistadores, who witnessed their construction materials first-hand.
So, for me there was some interesting speculation but at the end of the day much of it was just that. Many of David's ideas reminded me of Gavin Menzies' book, 1421, about a Chinese treasure fleet circumnavigating the globe a century before Magellan's expedition: a good yarn with possible basis in fact, but light on hard proof and only one of a number of alternative theories which fit the current evidence. It's great that David has taken the time to visit places and has even blown the dust off a few old ideas like Earth's Crust Displacement Theory, but for me he should be making a much better case for all the above. He also hedged his bets a tad, I felt, on who built this stuff: as-smart-as-us humans from now-lost civilisations, or Swedish-speaking levitating aliens banging magical Tibetan prayer drums with genetically-modified bananas?