New analysis of two spear-throwers excavated nearly a century ago in the Ozark Mountains reveals what one archaeologist calls an “uncanny” similarity to those used in the ancient Southwest and Mesoamerica. One of the artifacts — an intact carved wooden spear thrower, or atlatl — was first described in the 1920s, when it was found under a rock outcrop known as the Alred Shelter in northwestern Arkansas. The other, a large fragment of an atlatl of a different design, was uncovered in the 1930s at a site called the Montgomery Shelters in southwestern Missouri. The object was foreign enough to...