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R G Franciscus

Publications and source records attributed to R G Franciscus.

4 recordsLinked to original sources
PubMed1999

Neandertal nasal structures and upper respiratory tract "specialization".

Schwartz and Tattersall [Schwartz, J. H. & Tattersall, I. (1996) Proc. Natl. Acad. Sci. USA 93, 10852-10854] have argued for a previously unrecognized suite of autapomorphies in the internal nasal region of Neandertals that make them unique, not only among hominids, but possibly among all other terrestrial mammals. These purported autapomorphies include (i) the development of an internal nasal margin bearing a well developed and vertically oriented medial projection; (ii) a pronounced medial swelling of the lateral nasal wall into the posterior nasal cavity; and (iii) the lack of an ossified roof over the lacrimal groove. In addition, Laitman et al. [Laitman, J. T., Reidenberg, J. S., Marquez, S. & Gannon, P. J. (1996) Proc. Natl. Acad. Sci. USA 93, 10543-10545] pointed to these features as evidence for upper respiratory tract specializations among the Neandertals, indicating potential differences in behavior compared with modern humans. Critically reviewing the anatomical basis for Schwartz and Tattersall's contentions reveals several serious problems with their analysis, including (i) reliance on specimens with damaged, incomplete, or, in some cases, entirely absent relevant anatomy; (ii) failure to consider primary vs. secondary spatial consequences in nasal trait conceptualization; and (iii) failure to consider actual ranges of variation in these traits in both fossil and recent humans. Accordingly, the unique phylogenetic and adaptive "specializations" attributed to Neandertal internal nasal structures are unwarranted.

Animals↗
PubMed1991

Variation in human nasal height and breadth.

It has been suggested that the long-standing association of variability in the human nasal index [100 x (nasal breadth)/(nasal height)] with climatic variation is spurious evidence for natural selection in humans (Hoyme, 1965; St. Hoyme and Işcan, 1989). The argument is based principally on the observation that nasal height is globally more variable than nasal breadth, with nasal breadth thus contributing little to variation in the index. This argument does not take into account the confounding effect of absolute size of these variables on their variances. In this study we compare the intrinsic variation in skeletal nasal height and breadth within and among 26 mixed-sex populations (N = 2,408) at globally diverse localities (Howells, 1989), using 2 x 2 variance-covariance matrices of the logarithmically transformed variates. Hypothesis tests for homogeneity of matrices and equal-variance/equal-covariance indicate that the intrinsic variation in nasal breadth is greater than that for nasal height within populations, and that nasal breadth and nasal height exhibit equivalent intrinsic variation among populations. The argument that nasal breadth contributes little to the world-wide variation in the human nasal index is rejected. Given our present understanding of nasal physiological morpho-function, these results support, but do not demonstrate, an adaptive role for human nasal index variation. Promising methods for elucidating natural selection on human nasal form are suggested.

Analysis of Variance↗
PubMed1988

Nasal morphology and the emergence of Homo erectus.

Modern humans, among extant hominoids, possess a unique projecting, external nose whose basic structure is reflected in a series of skeletal features including nasal bone convexity, an internasal angle, lateral nasal aperture eversion, prominence and anterior positioning of the anterior nasal spine, an acute angle of the subnasal alveolar clivus, and an expansion of the breadth of the nasal bones relative to that of the piriform aperture. This anatomy appears with the emergence of Homo erectus ca. 1.6 million years ago. Although it undoubtedly evolved in the context of craniofacial and dental reduction during hominid evolution, it appears to have been primarily a response to the need for moisture conservation in an arid environment via turbulence enhancement and ambient cooling of expired air. Its appearance at this time in hominid evolution, in conjunction with the presence of a fatigue-resistant locomotor anatomy characteristic of archaic members of the genus Homo, indicates a shift to increasingly prolonged bouts of activity in open and arid environments.

Fossils↗