Biology Reference
In-Depth Information
CHAPTER
3
Age
-at-Death Estima
tion
Natalie M. Uhl
INTRODUCTION
Estimation of age-at-death from human skeletal remains provides a crucial element of the
biological profile. It typically is the first part of the biological profile to be assessed as the
subsequent analyses (sex, ancestry, stature) are treated very differently for juveniles versus
adults. The estimation of age-at-death from a human skeleton requires a thorough knowledge
and understanding of biological and physiological processes
d
both developmental and
degenerative
d
that affect the skeleton throughout life. It is assumed that the developmental
processes are under a great deal of genetic control and thus are less susceptible to environ-
mental influences. Populations exhibit differences in rate, timing, and duration of growth
through time; these are referred to as secular trends
1
and are generally attributed to environ-
mental factors like nutrition and exposure to disease agents. Degenerative processes inher-
ently involve more variation because they are due in large part to the environment
(nutrition, activity, occupation, etc.). For this reason, age-at-death estimates for adults require
much broader age ranges, while estimates for juveniles can be narrower, more precise ranges.
When an anthropologist estimates “age,” he or she is estimating biological age, that is,
noting the biological changes in the skeleton associated with time and activity. However,
chronological age, or calendar age, is the actual identifying feature of an individual. Chrono-
logical age is related to biological age, which allows us to use one to estimate the other,
but this relationship is imperfect for many reasons. For example, even though the skeleton
begins its development in utero, most societies exclude gestation from chronological age. Bio-
logical age is affected by activity and environment (e.g., nutrition, diet, disease load, stress),
whereas chronological age steadily progresses as days, months, and years. The effects of
environment and activity on biological but not chronological age make them gradually
more different from each other and introduce error into any estimate of one from the other.
Thus, age estimation for adults suffers frommore error and less precision than age estimation
for subadults (
Nawrocki, 2010
). This is particularly true for older adults
d
the variability
inherent in age estimation increases with chronological age, so that estimated ranges for
1
All bolded terms are defined in the glossary at the end of this volume.
