James McCanney who has a deep background in communications and physics has put forth the theory that the Nazca lines were designed specifically as a large scale interferometer fractal antenna complex. He said not only were these figures representations of animals but are also fractal antennas. Explaining how the complex is designed with dozens if not hundreds of dipole antennas some as long as 8 kilometers.
In his paper titled “The Nazca and Palpa Lines Peru – The Mystery Solved Ancient Interferometer Fractal Antenna Complex” (click to download) he believes this was either an ancient antenna array that was once covered in gold or another conductor and pillaged like most ancient ruins leaving no trace of the metal conductor or it was left by an alien civilization as a puzzle with the end goal of communication with them once we figure it out. Please read his paper for a detailed look at his theory.
Anyone who has not had the privilege to study James McCanneys work should visit his website at jmccsci.com. As a subscriber to his weekly paidcasts I have to say it is one of the most informative podcast I have ever listened to.