Cephalic index
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The cephalic index is the ratio of the maximum breadth of the head to its maximum length (i.e., in the horizontal plane, or front to back), sometimes multiplied by 100 for convenience. It was defined by Swedish professor of anatomy Anders Retzius (1796-1860) and first used in physical anthropology to classify ancient human remains found in Europe. It has been generally discredited since a study Franz Boas made at the turn of the 19th/20th century, and it became a tautology in anthropology that the cephalic index was a purely environmental component (Boas, however, did not himself claim it was totally plastic). In 2002 a paper by Sparks and Jantz re-evaluated some of Boas's original data using new statistical techniques and concluded that there was a "relatively high genetic component" of head shape.[1]
In adults, the index is no longer used except for describing individuals' appearances, and has no correlation with behavior. It is, however, still sometimes used for estimating the age of fetuses for legal and obstetrical reasons, in which case the differences in skull shapes between different populations are still of interest.
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[edit] Cephalic indices
Cephalic indices are grouped as
- < 75% (female), < 65% (male) : dolichocephalic, or 'long-headed'
- 75%-80% (female), 65%-75% (male) : mesocephalic, or 'medium-headed' (sometimes mesaticephalic)
- > 80% (female), > 75% (male) : brachycephalic, or 'short-headed'
The alternative terms mesocranial and brachycranial are also used.
Technically the measured factors are defined as the maximum width of the bones that surround the head, above the supramastoid crest (behind the cheekbones), and the maximum length from the most easily noticed part of the glabella (between the eyebrows) to the most easily noticed point on the back part of the head.
[edit] Brachycephalic animals
The terminology is also applied to animals, such as dogs and cats. Brachycephalic (snub-nosed) dogs and cats are very sensitive to high temperatures making the choice of a sleep or travel crate surface especially important.
List of brachycephalic (snub-nosed) dogs:
- American Staffordshire Terrier
- Boston Terrier
- Boxer
- Brussels Griffon
- Bull Terrier
- Dutch Pug
- English Bulldog
- English Toy Spaniel
- French Bulldog
- Japanese Spaniel (Japanese Chin)
- Japanese Pug
- Pekingese
- Shih Tzu
- Shar-Pei
- Staffordshire Bull Terrier
List of brachycephalic (snub-nosed) cats:
[edit] Dolichocephalic animals
List of dolicocephalic canines:
- Wolf
- Coyote
- Sighthounds such as
[edit] Mesocephalic animals
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[edit] See also
[edit] External link
[edit] References
- ^ Corey S. Sparks and Richard L. Jantz (November 2002). "A reassessment of human cranial plasticity: Boas revisited". PNAS 99 (23): 14636-14639. Retrieved on 2006-08-07.. See also the discussion in Ralph L. Holloway (November 2002). "Head to head with Boas: Did he err on the plasticity of head form?". PNAS 99 (23): 14622-14623. Retrieved on 2006-08-07.
