Biology Reference
In-Depth Information
A
B
C
D
FIGURE 3.4
Sternal ends of the fourth rib, progressing from youngest (A) to oldest (D).
first signs of change appeared in females at 14 years. This determination, however, was based
on one individual in the 10
e
15-year-old range. Any specimens younger than 14 years were
scored as “0.” The authors stated that morphological changes are so rapid between 14 and 28
years of age that phase differentiation could be made in 3 to 5 year intervals. As with the male
sample, observed ranges for each phase were very large, but the age range estimates were
reduced to 95% confidence intervals for the mean age of each stage.
Investigation into population differences in the morphology of the sternal extremity of the
rib continued for several years, primarily by I¸can and colleagues (
I¸can et al., 1985, 1987;
I¸can, 1991
). These studies found significant differences in the timing of morphological
changes for different sexes, ancestry groups, and even occupations.
I¸can et al. (1987)
pub-
lished new statistics and photos for ribs from African American males and females. While
these studies are widely used and cited, the sample sizes were usually not sufficiently large
to carry any statistical significance. For example, the African American female sample
included 14 individuals. While population differences may exist, methods based on such
small sample sizes cannot be used with confidence.
One of the most basic problems with the I¸can methods is the use of the fourth rib. Unless it
is removed at autopsy or the entire rib cage is available, the fourth rib could be misidentified.
Further, in archaeological or forensic contexts it could bemissing or broken.
Kunos et al. (1999)
suggested the use of the first rib because it is easily identifiable and less prone to breaking.
Their method not only focused on adult ribs, but included juvenile specimens as well. It is
unique amongst other aging methods because of its flowchart process that walks the anthro-
pologist through possibilities until the final use of a table to arrive at an age-at-death estimate.
Because the
Kunos et al. (1999)
method can be complicated to use and is of questionable
utility in practice,
DiGangi et al. (2009)
devised a simpler method for assessing age-at-death
from the first rib based on
Kunos et al.'s (1999)
observations of its morphological changes.
These authors limited the method to two morphological features of the first rib and provided
detailed descriptions and large color photographs of each phase. After scoring each feature,
an anthropologist can use the provided reference table for posterior densities derived from
transition analysis (given as 95% and 50% densities). The use and application of transition
analysis to provide reference tables for age-at-death estimation is not free from some of
the problems with age-at-death analysis, but it is the most statistically appropriate approach
