Forensic anthropology 14 3a circumscribed geographical area. Physical anthropologists have described
these diagnostic skeletal variations and their incidence within many popu-
lations, subgroups, and admixed groups elsewhere.27–31 Metric or statistical
assignment of ancestry involves comparisons of measurements from the
unknown remains with various means and ranges for the same measurement
within collections of known populations. Anthropologists sometimes employ
discriminant function tests in which many measurements from an unknown
are used collectively to assign a biological distance from the mean values of
the same measures in a collection of control individuals of known ancestry.
Such tests usually provide a statement about the likelihood of membership in
the reference group. In many instances, various limb proportion indices may
strengthen the statistical analysis, and these should be considered when the
inventory allows. Finally, no assignment of group membership is complete
without reference to nonmetric traits whose incidence within a particular
population approaches diagnostic threshold (e.g., os japonicum, shoveled and
winged incisors, tertiary third molar anatomy, rocker mandible, etc.). Just
as the pelvis is the complex of choice in assigning sex, the skull provides the
single most useful set of structures for attribution of ancestry. The dentition,
when present, provides an additional rich source of variation to support or
refine the assignment of population. Ultimately, the most difficult aspect of
the ancestry issue is the translation of detailed and often complex anatomical
and statistical findings into common “folk” or other vernacular typologies
that usually do not reflect biological reality, or into overly narrow database
categories that do not allow for findings of admixture or other useful infor-
mation. Forensic anthropologists’ reports should include the assignment of
biotype, within the limitations of the data, along with any additional infor-
mation about suspected admixture. Only when the biological population
has been described should the findings be translated into more widely used,
if less accurate, descriptive categories.
8.2.4.3 Skeletal and Dental Age
Tissues, organs, and systems mature at different rates. Some undergo renewal
throughout life while others decline or disappear altogether under the vary-
ing effects of wear, disease, nutrition, and trauma. Attempts to determine
the chronological age of a decedent at the time of death by any combination
of methods involving the hard tissues will result, at best, in an estimated
range. Under ideal circumstances, sufficient materials would be present to
allow both osteological and dental approaches to age determination. Dental
techniques, reported elsewhere in this volume, should correlate well with
skeletal assessments of age in individuals up to around fifteen or sixteen
years of age, and should provide reasonably comparable ranges up to about
twenty. Because full maturation of the skeleton requires half again as long
as the dentition, the former becomes increasingly more reliable as a basis for