Thomas E. Currie, Amy Bogaard, Rudolf Cesaretti, Neil R. Edwards, Pieter François, Phillip B. Holden, Daniel Hoyer, Aandrey Korotayev, Joe Mannin, Juan Carlos Moreno Garcia, Oluwole K. Oyebamiji, Cameron Petrie, Peter Turchin, Harvey Whitehouse, Alice Williams Agricultural productivity in past societies: towards an empirically informed model for testing cultural evolutionary hypotheses