Thigh and leg remains of Homo naledi

Rising Star Cave is located in the Cradle of Humankind World Heritage site near Krugersdorp in South Africa. In November 2013 and March 2014 more than 1500 hominin fossil elements attributed to a new species, Homo naledi, were recovered and catalogued representing at least a dozen individuals. Only 20 out of 206 bones in the human body are not in the collection as currently represented from the excavation. The thigh and leg of H. naledi, which are represented by 121 femoral, patellar, tibial, and fibular elements, are marked by a mosaic of primitive, derived, and unique traits that are functionally indicative of a bipedal hominin capable of long distance walking and, possibly, running. Traits shared with australopiths include a long, tall, and anteverted femoral neck, a mediolaterally compressed tibia, and a relatively circular fibular neck. Derived traits shared with Homo include a well-marked linea aspera, anteroposteriorly thick patellae, relatively long tibiae, and gracile fibulae with laterally oriented lateral malleoli. Unique features include the presence of two pillars on the superior aspect of the femoral neck and a strong distal insertion of the pes anserinus on the tibia. The mosaic morphology of the H. naledi thigh and leg appears most consistent with a species intermediate between Australopithecus spp. and H. erectus and, accordingly, may offer insight into the nature of the Australopithecus-Homo morphological transition. These fossils also expand the morphological diversity of the Homo lower limb, perhaps indicative of locomotor diversity in our genus.