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other aging techniques, the standard deviations were rather large, as were the observed
ranges. The authors noted that “the relationship between degree of closure and age is there-
fore only general” ( Meindl and Lovejoy, 1985 :62).
Meindl and Lovejoy also assessed the effect of ancestry and sex on the rate of suture
closure. Using “error in prediction” 11 as the dependent variable, no independent variables
or interactions were significant. Therefore, they concluded that sex and ancestry did not
contribute a measurable bias in age estimation from cranial suture closure. Despite their
moderately promising results, the authors still cautioned against the use of a single skeletal
indicator of age-at-death and encouraged further development of cranial suture closure as an
aging method.
Hershkovitz et al. (1997) published an article titled Why Do We Fail in Aging the Skull from
the Sagittal Suture?, a scathing critique trying to put to rest this “traditional research obses-
sion” of physical anthropologists (pp. 393 e 394). They quantified sagittal suture closure in
3636 skulls and found no useful age information after the age of 35 in addition to significant
sex and ancestry differences. The authors postulated that cranial suture closure patterns are
the result of a genetic predisposition for suture closure that differs between populations
because of biological adaptation. They concluded that “Suture closure is neither a patholog-
ical phenomenon nor the result of [a] normal aging process” ( Hershkovitz et al., 1997 :398).
In 1998, Nawrocki expanded on the work of Meindl and Lovejoy (1985) and Mann et al.
(1987, 1991) and developed a method of scoring 27 cranial landmarks along ectocranial,
endocranial, and palatal sutures. Nawrocki used 100 crania from the Terry Collection
including 50 females (25 European American and 25 African American) and 50 males
(24 European American and 26 African American), ranging in age from 21 to 85 years
with a mean age of 53.71 years. Importantly, no specimens were excluded from analysis
for any reason except postmortem damage. Sutures on the vault were scored in one centi-
meter segments on a four-point scale, in accordance with Meindl and Lovejoy's method.
Palatal sutures were observed along their entire length and are scored on the same scale.
Nawrocki's (1998) results revealed a moderate correlation between age and the summed
cranial suture score for an individual. The results of an ANCOVA found definite variance
resulting from sex, the interaction of ancestry and sex, and, of course, age. This interaction
effect led Nawrocki (1998) to develop ancestry and sex-specific regression equations. A
test of the equations on a different cadaver sample found that, as expected, the error rates
and inaccuracy increased, but only to levels similar to other skeletal aging methods.
Zambrano (2005) reevaluated and tested Nawrocki's methods and found that the general
“All Groups” equation outperformed the ancestry and sex-specific equations, based on the
percentage of individuals whose actual age fell within the
2 standard error interval. He
also reaffirmed that sex does in fact influence the rate and timing of cranial suture closure.
Probably most importantly, his tests for secular trends found Nawrocki's equations (devel-
oped on the earlier Terry Collection) to be appropriate for modern, forensic collections.
11 The authors define “error in prediction” as a linear combination of predicted minus actual age for each
individual plus or minus another factor that is dependent on sex, ancestry, or decade of age ( Meindl and
Lovejoy, 1985 ).
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