/anthropology/glossary/nasal-index
The nasal index is the breadth of the nose expressed as a percentage of its height. After the cephalic index it is the measure the classical literature used most, and it differs from that index in two respects that give this entry its shape. It is taken by three techniques whose scales do not overlap, so that a class name means nothing until the technique is known; and of all the measures in the glossary it is the one that most plainly follows climate, which bears directly on what a shared class can be taken to show.
Status: Preliminary. Scales are given from the standard handbooks and from the corpus's own table; the physiognomic landmarks remain to be confirmed against Martin's definitions.
lepto- λεπτός narrow, slender · meso- μέσος middle · platy- πλατύς broad, flat · chamae- χαμαί low · hyper- ὑπέρ beyond · -rrhine ῥίς, ῥιν- nose
A low index is a narrow nose, leptorrhine; a high index a broad one, platyrrhine; and the class between them is mesorrhine. Broca coined all three in 1872 for the skull. The German handbooks prefer chamaerrhine, "low-nosed", for the broad class, on the ground that a broad aperture in the skull is also a low one; the corpus keeps Broca's word. hyper- marks the bands beyond the narrow and the broad classes. The doubled rr is the rough breathing of the Greek root carried into the compound.
Three techniques exist, and they are set out separately because they measure different things.
On the skull, the craniological index takes the height from the nasion, the junction of the nasal and frontal bones, to the nasospinale, the lowest point of the margin of the nasal aperture, and the breadth as the greatest width of the aperture; the instrument is the sliding caliper, on bone. On the living, the morphological index takes the height from the nasion to the subnasale, where the septum meets the upper lip, and the breadth between the alare points, the outermost points of the wings of the nostrils. This is the technique of the German school and of most twentieth-century typologists, and because it measures cartilage and skin as well as bone, its values run far above the skull's. The physiognomic index, the technique of the Italian school, is the morphological with one change: the height is taken from the depth of the nasal root, the sellion, rather than from the nasion. The shorter height gives a higher index again.
The three sets of values are not convertible by a constant. The skull index concerns the bony aperture alone, while the living indices include the soft nose, whose form varies in part independently of the bone beneath it; and the two living indices differ in a landmark whose position varies with the profile of the face. A skull series and a living series from the same population may therefore fall in different classes with every measurement correct.
The corpus's source sets the three scales side by side, and the table follows it, with Broca's and Martin's for comparison. Read across any row: the same word, three ranges.
| Class | Skull, Broca (1872) | Skull, Martin (1914) | Skull, Eickstedt (1962) | Living, morphological (Eickstedt) | Living, physiognomic (Biasutti 1967) |
|---|---|---|---|---|---|
| hyperlepto- | — | — | –43 | –55 | –67 |
| lepto- | –47.9 | –46.9 | 43–47 | 55–70 | 67–77 |
| meso- | 48.0–52.9 | 47.0–50.9 | 47–51 | 70–85 | 77–87 |
| platy- (chamae-) | 53.0– | 51.0–57.9 | 51–58 | 85–100 | 87–97 |
| hyperplaty- | — | 58.0– | 58– | 100– | 97– |
Martin's living scale (hyperleptorrhine to 54.9, leptorrhine 55.0–69.9, mesorrhine 70.0–84.9, chamaerrhine 85.0–99.9, hyperchamaerrhine from 100) is the morphological scale the corpus follows, there attributed to Eickstedt. Broca's original skull scale had three classes; the outer bands were added by later authors.
The consequence is stated by the corpus's source itself: "the nasal indices published by different authors are not always comparable, because of different measuring techniques. This is sometimes ignored." A leptorrhine population in an Italian monograph and a mesorrhine one in a German monograph may have noses of the same form. It follows that before two authors' classes are compared, their techniques must be found, and before their numbers are compared, their landmarks.
Paul Broca defined the index on the skull in 1872 and named its three classes. His pupil Paul Topinard carried it to the living in the following decade, and since the living nose offered more than one way of fixing its height, the divergence of techniques began there. Rudolf Martin's Lehrbuch of 1914 fixed the skull and living scales that the German-language typologies used thereafter, and it is those typologies, digested by the corpus's source, that supply most of the corpus's descriptions.
The index's second life began outside typology. Arthur Thomson and L. H. Dudley Buxton, in 1923, set the means of populations against temperature and humidity and found the nose narrowing as the air grew colder or drier, a regularity still called Thomson's nose rule. J. S. Weiner sharpened it in 1954, showing that the index follows absolute humidity more closely than it follows temperature. Later work found the same gradient in the bony aperture of skull series, in Franciscus and Long's study of 1991, and in the internal nasal cavity, in that of Noback and others in 2011. The index has thus outlived typology, not as a marker of type but as a case in the study of adaptation, and the two careers should be kept distinct when its evidence is weighed.
The nasal index carries the strongest climatic signal of any measure of the head or face. Across the world's populations it correlates with absolute humidity more closely than any other index, and the mechanism is understood: a narrow, high nasal passage warms and moistens inhaled air more effectively than a broad one, which matters in cold or dry air and scarcely at all in warm humid air. Narrow noses accordingly cluster in the Arctic, in the deserts of North Africa and Arabia, and across the cold temperate north; broad noses in the humid tropics of Africa, South Asia, Southeast Asia and Melanesia.
From this the index's relation to descent follows directly. A trait that answers to climate will be shared by populations that share a climate, whatever their history, and will differ between related populations that straddle a climatic boundary. So it is here. The Arctic and the Sahara are both leptorrhine; equatorial Africa and New Guinea are both platyrrhine. The index sorts peoples by where their ancestors breathed, and that is geography rather than genealogy. The corpus's source records the climatic pattern and its likely cause; the conclusion it does not draw is that a shared nasal class is weak evidence of a shared type, and the reader should draw it.
The index is heritable, but its expression is partly soft tissue. The bony aperture is set early and inherited in the ordinary way; the cartilage and skin that the living indices include continue to grow into adult life and vary with age and sex. A living index therefore describes a population at an age as well as a population.
It is also entangled with its neighbours. A broad nose commonly accompanies a broad face and a projecting jaw, so that the nasal index is not an independent witness beside the facial index and prognathism; a typology that lists all three has listed one adaptation three times.
And it is the least comparable of the indices across sources, for the reason set out under the three techniques. No other measure in this glossary has scales that fail to overlap.
The judgment is accordingly this. The nasal index is a good measure of a real and functional feature of the face, and the clearest instance in the vocabulary of a trait shaped by environment rather than by ancestry. It describes well and classifies by descent badly. Its class names are conventions laid on three incompatible scales, and each carries its technique with it.
Of the 209 local varieties, 206 are placed on the index. A type written "(hyper-)platyrrhine" is counted under both bands, the parenthesis meaning that the extreme band is reached in part of the population; the compact form is far more frequent at the broad end of the scale than at the narrow.
| Class | Types | Examples |
|---|---|---|
| hyperleptorrhine | 21 | Aisto Nordid, Anatolid, Anglo-Saxon |
| leptorrhine | 85 | Hallstatt, African Alpinoid, Alföld, Amur-Sakhalin |
| mesorrhine | 68 | Aetid, Annamid, Aoshima |
| platyrrhine | 62 | Barrinean, Bobo, Brachio-Melanesid |
| hyperplatyrrhine | 18 | Central Bantuid, Bobo, Barrinean |
The corpus's descriptions are living, morphological values by the source's stated convention. Where the source's own literature drew on skull series or on the Italian authors, the class it gives has been read across scales, and a reader who wants the number behind a class must go to the author cited.
Nasal profile and root, for the form of the nose the index discards. Facial index and prognathism, the measures with which the nasal index is entangled. The cephalic index, for boundaries that differ by authority alone. The morpheme grid.
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