Figure 1.

The pre-Columbian peak of Amazonian soil charcoal. (a) Map of seasonality (number of months with more than 100 mm of rain) as determined from tropical rainfall monitoring mission (TRMM; Silman 2007), showing locations of soil charcoal ¹⁴C dated samples. (b) Two hundred and twenty-eight ¹⁴C ages for dated charcoal horizons in Amazonian soils (see Bush & Silman 2007 for review). All ages were calibrated using Calib v. 5.0.2 (Stuiver & Reimer 1993), and midpoint ages per 50-year period plotted against time (pink). Purple indicates atmospheric Δ¹⁴C as a proxy for solar output (Bard 1998). M, maunder; S, sporer; W, wolf solar minima. Turquoise indicates number of El Niño events per century (Moy et al. 2002).‘?’ indicates uncertainty as to the timing of a shift in Amazonian cultural adaptations.