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The cephalic index or cranial index is a number obtained by taking the maximum width (biparietal diameter or BPD, side to side) of the head of an organism, multiplying it by 100 and then dividing it by their maximum length (occipitofrontal diameter or OFD, front to back). The index was once used to categorize human beings in the first half of the 20th century, but today it is used to categorize dogs and cats.
The cephalic index was defined by Sweden professor of anatomy Anders Retzius (1796–1860) and first used in physical anthropology to classify ancient human remains found in Europe. The theory became closely associated with the development of racial anthropology in the 19th and early 20th centuries, when historians attempted to use ancient remains to model population movements in terms of racial categories. American anthropologist Carleton S. Coon also used the index in the 1960s, by which time it had been largely discredited.
In the cephalic index model, human beings were characterized by having either a dolichocephalic (long-headed), mesaticephalic (moderate-headed), or brachycephalic (short-headed) cephalic index or cranial index.
| mesocephalic; mesocranial |
| brachycranial |
Technically, the measured factors are defined as the maximum width of the bones that surround the head above the Temporal bone (behind the cheekbones), and the maximum length from the most easily noticed part of the Frontal bone (between the eyebrows) to the most easily noticed point on the back part of the head.
Boas argued that if craniofacial features were so malleable in a single generation, then the cephalic index was of little use for defining race and mapping ancestral populations. Scholars such as Earnest Hooton continued to argue that both environment and heredity were involved. Boas 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.. See also the discussion in Ralph Holloway of Columbia University argues that the new research raises questions about whether the variations in skull shape have "adaptive meaning and whether, in fact, normalizing selection might be at work on the trait, where both extremes, hyperdolichocephaly and hyperbrachycephaly, are at a slight selective disadvantage."
In 2003, anthropologists Clarence C. Gravlee, H. Russell Bernard, and William R. Leonard reanalyzed Boas's data and concluded that most of Boas's original findings were correct. Moreover, they applied new statistical, computer-assisted methods to Boas's data and discovered more evidence for cranial plasticity. In a later publication, Gravlee, Bernard and Leonard reviewed Sparks's and Jantz's analysis. They argue that Sparks and Jantz misrepresented Boas's claims, and that Sparks's and Jantz's data support Boas. For example, they point out that Sparks and Jantz look at changes in cranial size in relation to how long an individual has been in the United States in order to test the influence of the environment. Boas, however, looked at changes in cranial size in relation to how long the mother had been in the United States. They argue that Boas's method is more useful, because the prenatal environment is a crucial developmental factor.
Jantz and Sparks responded to Gravlee et al., reiterating that Boas' findings lacked biological meaning, and that the interpretation of Boas' results common in the literature was biologically inaccurate. In a later study, the same authors concluded that the effects Boas observed were likely the result of population-specific environmental effects such as changes in cultural practices for cradling infants, rather than the effects of a general "American environment" which caused populations in America to converge to a common cranial type, as Boas had suggested.
Note: Almost all representatives of the infraphylum Gnathostomata (with rare exceptions) are dolichocephalic.
(2025). 9781498736121, CRC Press. ISBN 9781498736121
Vertical cephalic index
The vertical cephalic index, also known as the length-height index, was a less-commonly measured head ratio. In the vertical cephalic index model, humans beings were characterized by having either a chamaecranic (low-skulled), orthocranic (medium high-skulled), or hypsicranic (high-skulled) cephalic index or cranial index.
Medicine
The cephalic index is also used in medicine, especially in the planning and effectiveness analysis of cranial deformity corrections. The index is a useful tool in assessing the morphology of cranial deformities in clinical settings. The index is used while looking at the fetal head shape, and can change in certain situations (ex. Breech birth, ruptured membranes, Twin). It can be measured for prenatal infants in the womb using obstetric ultrasound, and a value of 78.3% ± 8% (±2 standard deviations) is considered normal.Kintanar, T. A., & Fowler, Grant C., MD. (2020). Obstetric Ultrasound. In Pfenninger and Fowler’s Procedures for Primary Care (Fourth Edition, pp. 984–998).
Modern use in animal breeding
The cephalic index is used in the categorisation of animals, especially breeds of dogs and cats.
Brachycephalic animals
A brachycephalic skull is relatively broad and short (typically with the breadth at least 80% of the length). Dog breeds such as the pug are sometimes classified as "extreme brachycephalic". Because of health issues brachycephaly is regarded in some countries as "qualzucht", which literally translates to "torture breeding"FOUR PAWS International: The suffering of dogs with genetic disordersAnne Fawcett, Vanessa Barrs, Magdoline Awad et al.: Consequences and Management of Canine Brachycephaly in Veterinary Practice: Perspectives from Australian Veterinarians and Veterinary SpecialistsBorder Wars: Torture breedingFECAVA: Brachycephalic issues: shared resources as it often leads to brachycephalic airway obstructive syndrome.
List of brachycephalic dogs
List of brachycephalic cats
List of brachycephalic pigs
List of brachycephalic rabbits
Other
Mesaticephalic animals
A mesaticephalic skull is of intermediate length and width. Mesaticephalic skulls are not markedly brachycephalic or dolichocephalic. When dealing with animals, especially dogs, the more appropriate and commonly used term is not "mesocephalic", but rather "mesaticephalic", which is a ratio of head to nasal cavity. The breeds below exemplify this category. (1994). 9780721632001, Saunders. ISBN 9780721632001
List of mesaticephalic canines
List of mesaticephalic cats
Note: Almost all domestic felines are mesaticephalic (“medium-headed”)
List of mesaticephalic rabbits
Other
Dolichocephalic animals
A dolichocephalic skull is relatively long-headed (typically with the breadth less than 80% or 75% of the length).
List of dolichocephalic canids
Note: Almost all canidae are dolichocephalic
List of dolichocephalic felines
List of dolichocephalic leporids
Other
See also
External links
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