User blog comment:Ravager134K/my theory on the origin of the chimera/@comment-74.129.48.220-20100413110724

I also think that the pure Chimera later went to Earth themselves to build a tower or generator around the spires along with other locations around the world. They acted friendly towards the early humans at first to lull them into a false sense of security, but when they found out there were not enough viral hosts for an effective invasion, they destroyed any records they could find of themselves and buried their towers for use when the human population increased. They also modified their DNA to more effectively infect humans for later use after they retrieved human samples and/or bodies. The towers were (are) meant to signal the head Chimeran base on their original home world to begin the final stage of the invasion, contact the pure Chimera to launch a massive space armada.