The jury is still out. A lot of these studies were re-assessed and found to be quite faulty - i.e. you cannot bang two rocks together and get a perfectly flat

The jury is still out. A lot of these studies were re-assessed and found to be quite faulty - i.e. you cannot bang two rocks together and get a perfectly flat surface with <0.005mm deviation in flatness. Also, there is a lot of unexplained melted rock all over Peru and Ecuador and so on. Somebody in the ancient world either had a light sabre, or .. it was aliens.