Breakthrough in purification of fossil pollen for dating of sediments by a new large-particle on-chip sorter.

Particle sorting is a fundamental method in various fields of medical and biological research. However, existing sorting applications are not capable for high-throughput sorting of large-size (>100 micrometers) particles. Here, we present a novel on-chip sorting method using traveling vortices generated by on-demand microjet flows, which locally exceed laminar flow condition, allowing for high-throughput sorting (5 kilohertz) with a record-wide sorting area of 520 micrometers. Using an activation system based on fluorescence detection, the method successfully sorted 160-micrometer microbeads and purified fossil pollen (maximum dimension around 170 micrometers) from lake sediments. Radiocarbon dates of sorting-derived fossil pollen concentrates proved accurate, demonstrating the method's ability to enhance building chronologies for paleoenvironmental records from sedimentary archives. The method is capable to cover urgent needs for high-throughput large-particle sorting in genomics, metabolomics, and regenerative medicine and opens up new opportunities for the use of pollen and other microfossils in geochronology, paleoecology, and paleoclimatology.

Discontinuous spread of millet agriculture in eastern Asia and prehistoric population dynamics.

Although broomcorn and foxtail millet are among the earliest staple crop domesticates, their spread and impacts on demography remain controversial, mainly because of the use of indirect evidence. Bayesian modeling applied to a dataset of new and published radiocarbon dates derived from domesticated millet grains suggests that after their initial cultivation in the crescent around the Bohai Sea ca. 5800 BCE, the crops spread discontinuously across eastern Asia. Our findings on the spread of millet that intensified during the fourth millennium BCE coincide with published dates of the expansion of the Sino-Tibetan languages from the Yellow River basin. In northern China, the spread of millet-based agriculture supported a quasi-exponential population growth from 6000 to 2000 BCE. While growth continued in northeastern China after 2000 BCE, the Upper/Middle Yellow River experienced decline. We propose that this pattern of regional divergence is mainly the result of internal and external anthropogenic factors.