Assessing differences in the functional morphologic relationships of the nasal cavities of anatomically modern humans, Neanderthals, and mid‐Pleistocene Homo

Studies of the nasal cavities of anatomically modern humans (AMH), Neanderthals, and mid‐Pleistocene Homo (mPH) have traditionally approached analysis of species‐level differences by assessing where fossil specimens fall along the range of living humans. Both extinct hominin groups exhibit piriform aperture dimensions found among tropical AMH populations with some even exceeding them. It has recently been argued that a different set of functional relationships likely accounts for this pattern. This study assessed such differences via 3D Geometric Morphometric analyses. Coordinate data representing 29 facial, nasal, and basicranial landmarks were collected on a geographically diverse adult human sample (n=184; South East Asians, Chinese, West Africans, East Africans, North Africans, Southern Europeans, Northern Europeans, Alaskan Inuit, and Aboriginal Australians) and a pooled fossil sample (PFS) of Neanderthals (n=3) and mPH (n=4). PFS was pooled as all exhibit extremely broad piriform apertures (after Procrustes fitting of the total sample), tall‐narrow choanae, and narrow basicrania. When scaled over centroid size, the fossils exceeded most AMH specimens in all these measures but no significant ( P <0.05) differences were found between PFS and any single AMH population in the correlation of piriform aperture breadth to any of these measures. The only difference noted was that premaxilla length was significantly ( P <0.05) correlated with piriform aperture width only among PFS. However, when only landmarks bounding the nasal cavity (n=11) were used in a Generalized Procrustes Analysis, PFS exhibited greatest Procrustes and Malhalanobis distances from all AMH populations. Next, 2‐block Partial Least Square Analyses (PLS) and Modularity tests were ran on the AMH and PFS coordinate data via the MorphoJ program. Two PLS's were performed on each sample, one with a nasal block including only landmarks bounding the piriform aperture and the other PLS used a nasal block of landmarks bounding both piriform aperture, hard palate (i.e. nasal floor), and choanae. Both were significant ( P <0.001; 250 random permutations) among AMH but not PFS, suggesting that nasal landmark positions among AMH are not independent from those on the face and basicranium. Further analysis supported inclusion of piriform aperture, nasal floor, and choanal landmarks in a nasal module among PFS ( P <0.039, 10,000 random permutations). Additional modularity tests identifying only two blocks (three landmarks bounding piriform aperture versus all others) showed that the permutations with the least covariance include choanal landmarks among both AMH and PFS, suggesting that the choanal boundaries are among the most conservative structures. Given the closer relationship among PFS between the piriform aperture rim and the consistently tall‐narrow choanae as part of a module, this factor may account for the paradoxically broad piriform apertures of Neanderthals living in Pleistocene Eurasia. Support or Funding Information NSF Doctoral Dissertation Research Improvement Grant, BCS‐1128901