/anthropology/glossary/trunk-length
Relative trunk length is the share of standing height that the trunk contributes, or, what comes to the same thing, the length of the legs set against the trunk. Two ratios measure it: the skelic index, which sets leg length against sitting height, and the cormic index, which sets sitting height against stature. They carry the same information in opposite directions, and that would be a small matter if the words built on them had been used consistently. They have not. The class names have been used in two opposite senses, so that a description in one tradition reads backwards in the other, and the corpus follows the less common of the two. This entry is therefore concerned first with the proportion, which is among the best founded measures in the glossary, and then with the words, which are among the least reliable.
Status: Preliminary. Manouvrier's and Martin's boundaries are given from the standard handbooks; the corpus's source names its five classes without numerical bounds, and none are supplied here.
brachy- βραχύς short · meso- μέσος middle · macro- μακρός long · hyper- ὑπέρ beyond · -skelic σκέλος leg · -cormic κορμός trunk
Read by its elements, macroskelic is "long-legged" and brachyskelic "short-legged", and that is what the words mean in the tradition that coined them. The corpus's source, following Stratz, applies the same words to the trunk: its macroskelic types have long trunks and therefore short legs, and its brachyskelic types short trunks and long legs. The elements of the compound cannot settle which sense is meant, since each tradition can defend its reading. The -cormic terms, "short-trunked" and "long-trunked", have no such history and say the same thing in every author, which makes them the safer vocabulary where a choice is open.
Both indices rest on two measurements taken with the anthropometer. Stature is standing height, from the vertex to the floor, the subject erect with the head in the Frankfurt plane. Sitting height is from the vertex to the surface of the seat, the subject sitting erect on a flat surface with the thighs horizontal. Leg length is not measured directly but taken as the difference between them, which counts the legs from the seat and so includes a part of the pelvis.
The skelic index rises with leg length and the cormic index with trunk length. A skelic index of 100 marks legs and trunk of equal length, and the means of populations run from roughly 80 to 110. The cormic index runs from about 45 to 56 in the means of populations, as the corpus's source states: the trunk is a little under half of standing height in the longest-legged peoples and somewhat more than half in the shortest-legged.
Three schemes are in use. Manouvrier's is the original and names its classes by leg length; Martin's cormic classes name them by trunk length in words that cannot be misread; and Stratz's, which the corpus follows, names them by trunk length in the leg-length words.
| Proportion | Skelic index, Manouvrier (1902) | Cormic index, Martin (1914) | Stratz (1920), as used by the corpus |
|---|---|---|---|
| very long legs, very short trunk | — | — | hyperbrachyskelic |
| long legs, short trunk | macroskelic, 100– sub-macroskelic, 95.0–99.9 | brachycormic, –50.9 | brachyskelic |
| medium | mesatiskelic, 90.0–94.9 | metriocormic, 51.0–52.9 | mesoskelic |
| short legs, long trunk | brachyskelic, –84.9 sub-brachyskelic, 85.0–89.9 | macrocormic, 53.0– | macroskelic |
| very short legs, very long trunk | — | — | hypermacroskelic |
Stratz's four classes are named in his Naturgeschichte des Menschen of 1920; the fifth, hyperbrachyskelic, the corpus's source adds from Bernatzik (1943) for the longest-legged Nilotic peoples. The source gives no numerical bounds.
The inversion is complete. A Dinka is macroskelic to Manouvrier and hyperbrachyskelic in the corpus; an Inuit is brachyskelic to Manouvrier and hypermacroskelic in the corpus. Neither author is in error, since each is consistent within his own convention; but a reader who carries Manouvrier's sense, which is the sense the elements suggest and the sense most reference works give, will reverse every description in the corpus that uses these words. The remedy is to establish, for any text, which convention it follows before reading a single description, and the corpus's convention is stated here so that the reader need not establish it again.
Body proportion was measured long before it was indexed; the canons of the sculptors and the proportion studies of the Renaissance anatomists both set the legs against the trunk. As an anthropometric index it belongs to Léonce Manouvrier, who in 1902 set out the skelic index and its five classes in a study of the body's principal proportions, taking the trunk as the fixed reference on the ground that sitting height varies less between populations than leg length does. The cormic index, the trunk as a fraction of stature, was the form Martin's handbook preferred, with the transparent -cormic names.
C. H. Stratz, a gynaecologist who wrote widely on the human form, used the skelic terms in the trunk-length sense in his Naturgeschichte des Menschen of 1920, and it is from Stratz that the corpus's source takes its classes. The choice was not arbitrary in itself, for if the trunk is what one is describing, "long-trunked" is its natural name; but Stratz borrowed the leg-length words to say it, and the two traditions have run side by side since, mostly without noticing one another.
Outside typology the measure has had a steady life in human biology. Joel Allen had proposed in 1877 that the warm-blooded animals of cold climates have shorter extremities, and human leg length was soon found to follow the rule; D. F. Roberts in the 1950s and Christopher Ruff in the 1990s set human body proportions against climate systematically. Since the 1960s the relation of leg length to the conditions of childhood has made the same measurement an instrument of growth studies and of public health.
Relative leg length is one of the clearest geographic gradients in the human body. It increases from the Arctic toward the equator and from humid toward hot dry climates, as Allen's rule requires, since a long-legged and narrow body sheds heat and a short-legged and compact one conserves it. The longest legs among the world's populations are found among the Nilotic peoples of the hot Sudanic plains and the shortest among the Inuit and the peoples of the Siberian Arctic, with most of mankind in a broad middle band. The corpus's source rightly calls the measure "one of the most important, but often overlooked", and observes that it separates African populations that other measures do not.
The pattern is substantially inherited, and it is old. Within a population, proportion runs in families; between populations, the climatic gradient is visible in skeletal series many thousands of years deep, which is the reason it is taken as adaptive rather than accidental. The corpus's source goes further and holds that trunk length has "hardly continued to change" since the Neolithic. That is the source's judgment, and the secular changes noted next qualify it.
For leg length is the most plastic component of stature. The legs grow fastest in childhood and are most sensitive, in those years, to nutrition and disease; the trunk grows later and is better protected. The rise of stature across the industrialised world in the twentieth century was largely a lengthening of the legs, and short legs relative to the trunk now serve in epidemiology as a marker of a hard childhood. A population's proportion is therefore an inherited pattern overlaid with recent history, and a class assigned from series measured a century ago may not describe the same population's grandchildren.
Two further cautions concern the measurement. Proportion varies with age and sex, children being long-trunked and growing relatively longer-legged, and adult women having relatively longer trunks than men, so that series must be compared at like age and by sex or the classes are artefacts. And since the legs are taken as stature less sitting height, differences in the depth of the pelvis enter the index; the effect is small beside the climatic gradient, but it is not nothing.
The judgment, then, is favourable to the measure and unfavourable to the words. Relative trunk length is a well-founded, largely inherited and strongly climate-patterned proportion, more informative for comparison between distant populations than the cranial indices and less exposed to the plasticity that undermines the cephalic index, though not free of it. Its difficulty lies entirely in its vocabulary, which denotes opposite proportions in two traditions, and which must be read with its convention or not at all.
Of the 209 local varieties, 201 are placed on the index, in Stratz's trunk-length sense throughout. A type written "(hyper)brachyskelic" is counted under both bands.
| Class (corpus sense) | Proportion | Types | Examples |
|---|---|---|---|
| hyperbrachyskelic | very long legs | 15 | Dinkaid, Bobo, Casamance, Desert Australid |
| brachyskelic | long legs | 60 | Sudanid, Aisto Nordid, Barrinean |
| mesoskelic | medium | 123 | Hallstatt, Aetid, African Alpinoid |
| macroskelic | short legs | 59 | Alföld, Amur-Sakhalin, Annamid |
| hypermacroskelic | very short legs | 4 | Inuid, Bering Sea, East Bambutid |
The distribution follows the climatic gradient described above. The long-legged classes are West African, Nilotic and Australian; the short-legged are Arctic, Siberian and Southeast Asian, and the African Pygmy types stand among them, since their short stature is almost wholly a shortness of leg.
Stature, the absolute measure this proportion divides. Somatotype and build, for the other descriptions of the body the corpus gives. The cephalic index, for a measure with the opposite balance of inheritance and plasticity. The morpheme grid, and its third principle.
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