I'm not saying I believe any of the crazy conspiracies related to the Nazca lines, but I really do wonder what they actually are. The mysteries behind a lot of these ancient megalithic structures make me wonder about how sophisticated these presumed primitive civilizations actually we're.
Consider that while the invention of writing systems allowed us to store knowledge and grow our technology base, human intellect and capacity hasn't changed in any real sense over at least the past 50,000 years.
The human ability to reason, imagine and create has existed for tens of millenia. As such, such sophistication isn't all that surprising.