The atlatl is a handheld, rod-shaped device that employs leverage to launch a dart, and represents a major human technological innovation. One hypothesis for forager atlatl adoption over its presumed predecessor, the thrown javelin, is that a diverse array of people could achieve equal performance results, thereby facilitating inclusive participation of more people in hunting activities. We tested this hypothesis via a systematic assessment of 2160 weapon launch events by 108 people who used both technologies. Our results show that, unlike the javelin, the atlatl equalizes the velocity of female- and male-launched projectiles. This result indicates that a javelin to atlatl transition would have promoted a unification, rather than division, of labor. Moreover, our results suggest that female and male interments with atlatl weaponry should be interpreted similarly.

Background A novel physis in hominins modulates broadening and shortening of the ilium. We report analysis of a vascular canal system whose origin may be associated with this physis and which appears to be also unique to hominins. Its presence is potentially identifiable in the fossil record by its association with a highly enlarged foramen that is consistently present in modern humans and hominin fossils. Methods We measured the diameter of this foramen in humans, fossil hominins, and African great apes and corrected for body size. Results The mean relative human foramen diameter is significantly greater than those of either Pan or Gorilla . Moreover, eight of the nine values of the Cohen’s d for these differences in ratios are highly significant and support the ordering of magnitudes: Pan < Gorilla < Homo . The relative foramen diameter of A.L. 288-1 is above the 75th percentile of all other hominoids and at the high end of humans. The foramen is also present in ARA-VP-6/500. Conclusions We posit that the presence and significant enlargement of this foramen in fossils can reasonably serve as an indicator that its anterior inferior iliac spine emerged via the unique hominin physis. The foramen can therefore serve as an indicator of hominin iliac ontogenetic specialization for bipedality in fossil taxa.

SignificanceThe human ilium is unusually short and broad compared with those of all other primates. Its specialized shape facilitates pelvic control during upright walking. Our ilium also exhibits a unique developmental feature: Its anterior inferior spine forms via a secondary center of ossification. We surveyed iliac development in a wide range of fetal to adult nonhuman primates, and found that such specialized anterior inferior spine formation is unique to humans and our known ancestors. Because this derived iliac structure facilitates upright walking, its presence serves as a direct indicator of the adoption of terrestrial bipedality in the fossil record and as an indicator of the minimum age of that adoption.