Homo naledi strides again: preliminary reconstructions of an extinct hominin’s gait

In this preliminary reconstruction of Homo naledi’s gait we begin with the null hypothesis that it walked similarly to modern humans, as the overall anatomy of this extinct hominin’s lower limb, especially its foot, is mostly modern human-like. We note the following characters as modern-like: dorsally-canting metatarsophalangeal joints facilitating toe-off, locking transverse tarsal joint implying a rigid midfoot during stance, flat subtalar joint limiting ankle pro- and supination, talocrural joint oriented orthogonally to the substrate, valgus knee, thick patellae increasing the moment arm for quadriceps femoris, and well-developed thigh muscle attachment sites throughout the femur. These characters suggest Homo naledi was welladapted to a striding bipedal gait. However, we also note the following less modern-like characters: curved pedal phalanges, low sustentaculum tali and likely a low fundamental longitudinal arch, pronounced tubercular insertion of the pes anserinus tendon on the proximomedial tibia, long femoral neck with a marked medial encroachment of the obturator externus, posteriorly positioned ilium relative to the acetabulum, flared iliac blades, broad lower ribcage, and characters of the lower thoracic vertebrae and lower rib suggesting robust hypaxial muscles. We offer our initial functional interpretations of the cumulative postcranial morphology, which suggests different trunk stabilization from modern humans but is consistent with orthogrady and an obligate bipedal locomotor regime. Given the anatomy of the upper limb, Homo naledi demonstrates coexistence of both bipedalism and climbing adaptations in one hominin taxon.