Deep learning reveals extent of Archaic Native American shell-ring building practices

In the mid-Holocene (5000 - 3000 cal B.P.), Native American groups constructed shell rings, a type of circular midden, in coastal areas of the American Southeast. These deposits provide important insights into Native American socioeconomic organization but are also quite rare: only about 50 such rings have been documented to date. Recent work using automated LiDAR analysis demonstrates that many more shell rings likely exist than are currently recorded in state archaeological databases. Here, we use deep learning, a form of machine intelligence, to detect shell ring deposits and identify their geographic range in LiDAR data from South Carolina. We corroborate our results using synthetic aperture radar (SAR), multispectral data, and a random forest analysis. We conclude that a greater number of shell rings exist and that their distribution expanded further north than currently documented. Our evidence suggests that ring-construction was a more widespread and common practice during the mid-Holocene

Beveled Projectile Points and Ballistics Technology

Explanations for beveled blade edges on projectile points have been debated in North America archaeology since the first systematic description of lithic assemblages in the nineteenth century. Debate has centered around two opposing perspectives. One views beveled edges as features of projectile points that cause them to spin during flight. The other views beveling as a product of edge resharpening that is done unifacially to conserve scarce resources. Here we use a fluid-dynamics model to simulate the effect beveling has on projectiles. Expectations derived from this modeling are evaluated using wind-tunnel experiments. Our findings indicate that beveling produces in-flight rotation that serves as a means of increasing accuracy in relatively low-velocity flight paths.