Table 2.

Wheat washing chronology after provisioning at Koshima began in 1952.

Kawai et al. (1992), Watanabe (1994), and Hirata et al. (2001)

Stages of apparent cultural change	Year first observed	Description of act	Cumulative improvement
1. Throw	1956	Carry and drop sand/wheat mixture into water, separating wheat from sand. Skim floating wheat off surface	Grains separated from grit, so more easily consumed. Cleaner foodstuff saves wear on teeth and may reduce risk of parasites
2. Attack and plunder	1959	‘Muggers’ threaten and attack wheat washer and take grains	Labor-saving, as less energy expended collecting and washing
3. Scavenge	1962	Collect wheat grains floating downstream or in sea	Labor-saving, as less energy expended collecting and washing
4. Dribble	1970	Grasp sand and wheat mixture in hands, then repeatedly drop small amounts into water to prevent snatching by others	More secure processing against attacker/plunderers. More controlled to reduce loss of grain in water current or waves
5. Sweep	1971	Sweep wheat grains next to water’s edge by hand into water	Labor-saving: less energy expended collecting and washing
6. Screen	1974	Grasp mixture in hands, then shake in water. Sand removed with grains remaining in clenched fists	More controlled than throwing. Increased security against attacker/plunderers
7. Mobile screen	1974	Walk into water while grasping mixture in hands while screening	More controlled than throwing. Increased security against attacker/plunderers
8. Private pool	1983	Dig small depression in sand, then sweep wheat grains into resulting pool and skim off surface	Increased security against scavengers/plunderers. Labor-saving, and more controlled than the other variants—loss of wheat grains prevented