How the pyramids could have been made
1. Tie a rope to a block.
2. Run the rope all the way over the top of the pyramid and down the other side and onto the ground.
3. With many people on the ground, pull the block up the pyramid from the other side of the pyramid.
4. Probably have a few people walking up with the block (if it's too steep they could tie themselves to the rope) in order to a) make it slide easily by using rollers, and b) guide it to the right place and/or set it in position when it gets there.