Biology Reference
In-Depth Information
SEX ASSESSMENT VERSUS SEX ESTIMATION
Spradley and Jantz (2011)
draw a distinction between sex assessment and sex estimation
(as per a previous communication with Stanley Rhine), which is worth emphasizing. Sex
assessment refers to the traditional and more subjective visual method used by anthropolo-
gists when looking at elements such as the pelvis or skull. Sex estimation, in contrast, is the
metric estimation of sex using estimable error rates (
Spradley and Jantz, 2011
).
Stewart
(1979)
recommended using metric sex estimation only as a validation of the more subjective
visual sex assessment. The current consensus in sexing research, however, is to focus on
metric sex estimation. This is demonstrated by the vast proportion of recent papers based
on discriminant function analysis of metric traits versus publications on descriptive,
nonmetric traits.
Though many researchers may publish papers claiming sex determination (
Berrizbeitia,
1989; Kemkes-Grottenthaler, 2005; Rogers, 2005; Barrio et al., 2006; Case and Ross, 2007;
Gualdi-Russo, 2007; Mahfouz et al., 2007a; Albanese et al., 2008
), I believe this term is
incorrectly used and implies greater confidence than is warranted. Until accuracy rates
consistently reach 100% (which will likely never happen due to human variation), it is better
to consider this endeavor as estimation of sex.
Another common error in terminology made in some publications is the incorrect use of
the term gender instead of sex (
Gilsanz et al., 1997; Beck et al., 2000
). Gender is a sociocultural
construct, whereas sex is a biological distinction (
Walker and Cook, 1998
). The latter term
reflects what can be discerned from analysis of the human skeleton, though culture inevitably
plays a role, as will be discussed.
Anthropologists traditionally used visual inspection of sexual dimorphism of the pelvis
and skull to distinguish a male skeleton from a female one. The adult female skeleton main-
tains prepubescent gracility (except in the pelvis), whereas the adult male skeleton shows
more robusticity than the female skeleton (especially at muscle insertion sites) in most cranial
and postcranial elements (
Stewart, 1979; Krogman and I¸can, 1986; Bass, 1987
). For the
purpose of childbirth, the female pelvis continues to grow and change shape until the age
of about 18, but the male pelvis maintains prepubescent characteristics (see discussion
below) (
Buikstra and Ubelaker, 1994; Bogin, 1999
).
Brothwell considered the traits that are “sexed upon inspection” to be the most impor-
tant, especially those on the pelvis and skull (
Brothwell, 1963
).
Stewart (1979)
considered
the method of looking at observable sex details (e.g., subpubic angle, size of the mastoid
process) to be the simplest indicator of sex. He considered it to be a waste of time to
measure traits that can be verified very quickly by the naked eye. Rogers wrote that
nonmetric traits were “of more immediate value” to the forensic anthropologist because
they required less time and effort than metric sex estimation (
Rogers, 1987
). More recently,
calls for higher standards in the legal system have caused a shift toward greater emphasis
on validation studies and the use of estimable error rates within skeletal biology. Before
reviewing the various methods for sex estimation and assessment, a discussion about
the various causes for sexual dimorphism (both intrinsic and extrinsic) will help keep
a focus on the etiology of the sexual dimorphism that we use to estimate and assess sex
from the skeleton.
