Matthew Waters, Mark Brenner and colleagues dated sediment cores from two lakes beside ancient Maya settlements in the northern Yucatán. Mercury, linked to the Maya use of cinnabar (red pigment) and elemental mercury, exceeded modern sediment toxicity thresholds for centuries between about 40 and 820 CE, peaking around 720 CE at Cenote Xcach. In the same layers, markers for algae, cyanobacteria, ostracods, snails and midge larvae declined or vanished, and recovered when mercury fell.
Jianbo Guo, Ruochen Ge, Lu Yang and colleagues studied textile residues on objects from the Sanxingdui sacrificial pits K2–K8, the site of the famous bronze heads and gold masks of the ancient Shu culture. They found silk on 101 objects, 94 of them bronzes, dating to the Late Shang period (1300–1046 BCE). Microscopy and infrared tests identify mulberry silk, mostly plain weave, some coloured with hematite or an organic red dye, and some cloths as finely woven as Shang silks from the Central Plains.
Kelly Graf, Ted Goebel and colleagues report on Shég’ Xdaltth’í’ (formerly McDonald Creek), 55 km south-southeast of Fairbanks. It has three Late Pleistocene occupation layers dated to about 13,800, 13,000 and 12,700 years ago. The oldest layer holds more than 80,000 specimens, including a distinctive hafted biface, bone and antler tools, animal remains and well-preserved activity areas.
Kathleen Springer, Jeffrey Pigati, Jessica Tierney and colleagues expanded the excavations at White Sands and found 20 stratigraphic layers with human footprints in place, alongside megafauna trackways and drag lines made by travois. New radiocarbon dates on conifer pollen, combined with dates on aquatic seeds, put the footprint sequence between 23,500 and 21,700 years ago. Pollen, biomarker and sediment data record the lake turning into a playa during a dry spell that matches Dansgaard-Oeschger event 2, about 23,200 years ago.