They wrote that 69% of the specimens contained maize starch grains, the dominant source of starch in the diet at that time.

BBC: Maize was key in early Andean civilisation, study shows

PLAs are formed when molecules of lactic acid (which is obtained, in this case, from maize starch) join together to form long chains.

ECONOMIST: Evanescent or evergreen?

"Eleven of the 14 tools had predominantly or exclusively maize starch grains on the working surfaces, and two working surfaces had maize phytoliths (mineral excretions by the plant), " they recorded.

BBC: Maize was key in early Andean civilisation, study shows