An early shift from wetland-adjacent to upland farming in the Maya lowlands

Abstract

Maize is a seed grain of global social and economic importance. It has a mutualistic relationship with humans that evolved in parallel with the decisions of farmers who intensified its production. This occurred in the context of climate change, human selection for improved varieties, and increasing dietary importance. However, empirical documentation of human-maize dynamics is incomplete. Maize domestication was underway by 8900 BP in the neotropics and underwent selection over millennia while transitioning from a minor wetland-adjacent crop to a staple grain. We generated multiproxy isotopic, microbotanical, and paleoecological evidence that demonstrate a shift from extensive wetland-adjacent C4 plant cultivation by 6000 BP to upland C4 plant cultivation away from wetlands by 3500 BP when early maize is being intensively cultivated. We link these processes to early land clearing, niche construction, and population growth following a dry interval as people reassessed risk in response to climate uncertainties. A subsequent steep decline in wetland-adjacent farming after 4000 BP corresponds with the establishment of upland farming settlements. Data from Belize document a shift from wetland-adjacent maize farming at 6,000 BP to upland maize farming by 3,500 BP correlating with climate change and population growth, as shown by multiproxy palaeoecological and isotopic data that track farming and landscape disturbance.