Superb article, I remember a BBC program in the 1960's showing the use of a Australian Aboriginal Woomera, not as beautifully carved as this Atlatl, just a deeper channel that the 1/2 to 2/3 rds of the spear lay in, with a "tooth" that sat up and connected with the end of the spear, sort of self centering; it was a lot longer therefore I would think probably took longer to master.
John