The tall and narrow body shape of anatomically modern humans (Homo sapiens) evolved via changes in the thorax, pelvis and limbs. It is debated, however, whether these modifications first evolved together in African Homo erectus, or whether H. erectus had a more primitive body shape that was distinct from both the more ape-like Australopithecus species and H. sapiens. Here we present the first quantitative three-dimensional reconstruction of the thorax of the juvenile H. erectus skeleton, KNM-WT 15000, from Nariokotome, Kenya, along with its estimated adult rib cage, for comparison with H. sapiens and the Kebara 2 Neanderthal. Our three-dimensional reconstruction demonstrates a short, mediolaterally wide and anteroposteriorly deep thorax in KNM-WT 15000 that differs considerably from the much shallower thorax of H. sapiens, pointing to a recent evolutionary origin of fully modern human body shape. The large respiratory capacity of KNM-WT 15000 is compatible with the relatively stocky, more primitive, body shape of H. erectus.

解剖学上的现代人（智人）高而窄的身体形状是通过胸腔，骨盆和四肢的变化而演变而来的。然而，这些修饰是否首先在非洲直立人中一起进化，或者直立人螺旋体是否具有更原始的体形（与更像猿类的南方古猿物种和智人）不同，尚有争议。在这里，我们介绍了肯尼亚纳里奥科托姆市幼年直立人骨骼的胸骨KNM-WT 15000的首次定量三维重建，以及其估计的成年肋骨，以便与智人进行比较和Kebara 2尼安德特人。我们的三维重建显示了KNM-WT 15000中的短，中外侧宽和前后深的胸腔，与智人的较浅胸腔有很大不同，这表明了近代人完全塑形的进化起源。KNM-WT 15000的大呼吸能力与直立螺旋杆菌相对矮胖，更原始的体型相适应。