Sedentism and plant cultivation in northeast China emerged during affluent conditions

The reasons and processes that led hunter-gatherers to transition into a sedentary and agricultural way of life are a fundamental unresolved question of human history. Here we present results of excavations of two single-occupation early Neolithic sites (dated to 7.9 and 7.4 ka) and two high-resolution archaeological surveys in northeast China, which capture the earliest stages of sedentism and millet cultivation in the second oldest center of domestication in the Old World. The transition to sedentism coincided with a significant transition to wetter conditions in north China, at 8.1–7.9 ka. We suggest that these wetter conditions were an empirical precondition that facilitated the complex transitional process to sedentism and eventually millet domestication in north China. Interestingly, sedentism and plant domestication followed different trajectories. The sedentary way of life and cultural norms evolved rapidly, within a few hundred years, we find complex sedentary villages inhabiting the landscape. However, the process of plant domestication, progressed slowly over several millennia. Our earliest evidence for the beginning of the domestication process appear in the context of an already complex sedentary village (late Xinglongwa culture), a half millennia after the onset of cultivation, and even in this phase domesticated plants and animals were rare, suggesting that the transition to domesticated (sensu stricto) plants in affluent areas might have not played a substantial role in the transition to sedentary societies

Data from: A novel mechanism of mixing by pulsing corals

The dynamic pulsation of the xeniid corals is one of the most fascinating phenomena observed in coral reefs. We quantify for the first time the flow near the tentacles of these soft corals whose active pulsations are thought to enhance their symbionts' photosynthetic rates by up to an order of magnitude. These polyps are about 1 cm in diameter and pulse at frequencies between about 0.5 and 1 Hz. As a result, the frequency based Reynolds number calculated using the tentacle length and pulse frequency is on the order of 10 and rapidly decays as one moves away from the polyp. This introduces the question of how these corals minimize the reversibility of the flow and bring in new volumes of fluid during each pulse. We estimate that the Peclet number of the bulk flow generated by the coral as being on the order of 100-1000 while the flow between the bristles of the tentacles as being on the order of 10. This illustrates the importance of advective transport in removing oxygen waste. Flow measurements using particle image velocimetry reveal that the individual polyps generate a jet of water with positive vertical velocities that do not go below 1 mm/s and with average volumetric flow rates of about 700 cubic mm per second. Our results show that there is nearly continual flow in the radial direction towards the polyp with only about 3.3 percent back flow. 3D numerical simulations uncover a region of slow mixing between the tentacles during expansion. We estimate that the average flow that moves through the bristles of the tentacles are about 0.3 mm/s. The combination of nearly continual flow towards the polyp, slow mixing between the bristles, and the subsequent ejection of this fluid volume into an upward jet ensures the polyp continually samples new water with sufficient time for exchange to occur

four_polyp_xeniid

This zip file contains raw images of four xeniid coral polyps pulsing. The corals and particles in the fluid are illuminated with a laser sheet

single_xeniid_polyp

This zip file contains raw images of a single xeniid coral polyp pulsing for several cycles. The coral polyp and the particles in the fluid are illuminated with a laser sheet

Sedentism and plant cultivation in northeast China emerged during affluent conditions.

The reasons and processes that led hunter-gatherers to transition into a sedentary and agricultural way of life are a fundamental unresolved question of human history. Here we present results of excavations of two single-occupation early Neolithic sites (dated to 7.9 and 7.4 ka) and two high-resolution archaeological surveys in northeast China, which capture the earliest stages of sedentism and millet cultivation in the second oldest center of domestication in the Old World. The transition to sedentism coincided with a significant transition to wetter conditions in north China, at 8.1-7.9 ka. We suggest that these wetter conditions were an empirical precondition that facilitated the complex transitional process to sedentism and eventually millet domestication in north China. Interestingly, sedentism and plant domestication followed different trajectories. The sedentary way of life and cultural norms evolved rapidly, within a few hundred years, we find complex sedentary villages inhabiting the landscape. However, the process of plant domestication, progressed slowly over several millennia. Our earliest evidence for the beginning of the domestication process appear in the context of an already complex sedentary village (late Xinglongwa culture), a half millennia after the onset of cultivation, and even in this phase domesticated plants and animals were rare, suggesting that the transition to domesticated (sensu stricto) plants in affluent areas might have not played a substantial role in the transition to sedentary societies