More recent: http://chsi.harvard.edu/markone/images/HumanComputers.jpg
Putting humans into rows and columns, performing the same tasks, is common pretty much anywhere you look.
The list is a (the?) fundamental data structure, and the two dimensional list is an easy extension.
For those who desire control over other humans, it's an easy way to check that things are (superficially) in line.
[] The trireme design is an arguably effective arrangement in terms of moving a boat.
