A virtual, three-dimensional reconstruction of the thorax of an adult, male Neandertal is presented in Nature Communications this week. The analysis suggests that the thorax of Neandertals had a similar size to that of modern humans, but had a different shape. Based on this, the authors propose that Neandertals may have had a subtly different breathing mechanism to modern humans.
The size and shape of the Neandertal thorax has been the subject of scientific debate since the first discovery of Neandertal ribs more than 150 years ago. Interpretations have ranged from a morphology that is indistinguishable from modern humans, to one that was significantly different.
Asier Gomez-Olivencia and colleagues reconstructed the most complete adult Neandertal thorax found to date: that of Kebara 2 (K2). The authors found that their reconstruction had a similar sized skeletal thorax to modern humans, but is wider in its lower segment.
The authors suggest that in K2, the diaphragm had a larger surface owing to the larger diameters of the lower thorax. Analyses show that a rib cage with a wider lower segment would produce greater overall size increments (respiratory capacity) during inspiration. The authors hypothesize that the Neandertal breathing mechanism relied relatively more on diaphragm contraction than modern humans do.
The authors note that additional fossils and further studies are necessary to understand the evolution of this anatomical region.