Biology Reference
In-Depth Information
a measurement of the length of the transparent portion of the root. That measurement is then
entered into a single regression formula regardless of sex or ancestry of the individual.
Prince
and Ubelaker (2002)
validated the method's accuracy on a diverse skeletal sample, made
adjustments, and found that although it was developed on a French population, it worked
well for an American cadaveric sample, with mean errors around 8 years. When
Prince
and Ubelaker (2002)
accounted for sex and ancestry the errors were further reduced to as
low as 6.24 years for African American females. For more information on dentition, refer
to Hammerl (Chapter 10), this volume.
Histology
Human bone is a dynamic tissue that constantly remodels in response to stressors in
addition to being responsible for homeostasis of blood levels of minerals like calcium and
phosphorus (
Saladin, 2010
). The basic organizational unit of cortical (compact) bone is the
osteon. As a person ages, primary osteons are broken down (sometimes not completely)
and replaced by new (secondary) osteons, presumably at a predictable rate. This turnover
rate is the basis for histomorphological methods of age-at-death estimation (
Stout, 1998
).
These methods are not widely used by anthropologists because of the need for both special-
ized knowledge and specialized equipment to prepare and examine histological slides of the
cortical bone (not to mention the destruction caused when obtaining the histological section),
but when applied, these methods have potential to provide more precise age-at-death esti-
mates for older individuals (
Crowder and Pfeiffer, 2010
).
Kerley (1965)
was the first to publish an applicable method of age-at-death estimation
based on histomorphology, but many have since followed with population-specific work,
larger samples, and different bones (i.e., femur, rib, mandible, etc.), each leading to a different
regression equation (e.g.,
Thompson, 1979; Stout and Paine, 1992; Cho et al., 2002
). These
methods still suffer from large age ranges, high interobserver error with osteon counts,
and the possible impact of disease or metabolic changes that affect osteon turnover on an
individual basis. For more information on histology, refer to Trammell and Kroman (Chapter
13), this volume.
Multifactorial Methods
Most biological anthropologists rely on multiple skeletal indicators of age-at-death when
estimating age but lack a statistically sound method for combining individual indicators.
Attempts at multifactorial aging (e.g.,
Brooks, 1955; Lovejoy et al., 1985a
) have had generally
disappointing results because they typically rely on either nonstatistical or linear statistical
methods, creating problems with validity and applicability.
The first attempt at combining two or more skeletal aging methods was conducted
by
Brooks (1955)
, who utilized Todd's studies of cranial suture closure and changes
of the pubic symphyseal surface in a skeletal population of prehistoric Native Ameri-
cans and the Hamann Collection (now the Hamann-Todd Collection). She did not
combine these two methods statistically but applied both methods to each individual
in her sample. For the cadaveric Hamann Collection the correlation between pubic
symphysis age and known age was acceptable in most cases but the correlation
between cranial suture closure and known age was very low. In the prehistoric Native
