The pyramids were built by ancient humans, not alien visitors. In Egypt, the people who built the pyramids were most likely voluntary laborers and skilled craftsmen. Archaeologists have found the tombs of some of the people who designed and built the pyramids.
The primary argument for extraterrestrial assistance in building the pyramids is that ancient peoples did not have the necessary technology to accomplish the monumental task. However, archaeologists have discovered evidence of the techniques used to transport materials and shape the pyramids. Wall paintings show some of the techniques used, such as using sleds and wet sand to help move the heavy stone blocks across long distances.