Biology Reference
In-Depth Information
In order to improve upon the Phenice method and decrease its subjectivity, Bruzek (2002)
used five measurements from the pelvis including a combination of the Phenice method, the
preauricular sulcus, the greater sciatic notch, and inferior morphology including the ischio-
pubic index. These characters were chosen to reflect more sex-specific functional adaptations
of bipedality and the investigator achieved an accuracy rate of 95% ( Bruzek, 2002 ). Future
research could test whether this method has reduced subjectivity compared to the Phenice
method alone. As mentioned above, most textbooks have extensive descriptions and lists
of features established for sex assessment, sometimes having been ranked for their reliability.
Studies are beginning to investigate error rates in sex assessment and this would be a possible
area of future research ( Rogers and Saunders, 1994; Konigsberg and Hens, 1998; Bruzek, 2002;
Ubelaker and Volk, 2002; Walker, 2008 ).
Sex Assessment: Skull
The morphology of the skull has been the most studied part of the skeleton. Broca pub-
lished the first scoring illustrations of sex assessment from the skull in 1875 ( Wa lker, 2008 ).
Visual sex assessment is relatively simple and does not require any anthropometric
equipment; however, it can be difficult to measure the traits being visually assessed
(e.g., the morphology of the brow ridge) ( Walker, 2008 ). The chin of the male mandible is
more square-shaped, whereas the female chin is more rounded. Male skulls are more
robust, especially at muscle insertion sites. The female skull is typically more gracile,
but analysis must be limited to adult ages between approximately 20 and 55 years, 5 as
masculinization of the skull occurs with older age in females and younger males may
not yet have developed secondary sex characteristics in the skull ( Krogman and I¸can,
1986; Buikstra and Ubelaker, 1994 ).
It is important for a researcher to be very familiar with the pattern of variability within a
population, because morphological features on the skull are population specific ( Buikstra
and Ubelaker, 1994 ). For example, one population may have males with very robust brow
ridges, while another population may have males with relatively gracile brow ridges and
less sexual dimorphism between males and females, as a result of human variation. For
this reason, ordinal ranking of traits from 0 to 5 as per Buikstra and Ubelaker (1994) are rec-
ommended for discrimination (score of 0 as indeterminate, 1 as smallest or absent, 5 as
largest). Walker (2008) preferred this ranked ordinal standard as opposed to the
2to2
system developed by Asc ´ di and Nemesk ´ ri (1970). In this system in which 0 is intermediate
between male traits and female traits, 0 in one population may not be a 0 in another
population.
Comparative population studies are needed to investigate intrinsic and universal female
or male traits versus those traits that are population specific or represent a continuum of
expression between populations. Population variation in discrete and metric traits is dis-
cussed further in the chapter on ancestry estimation in this volume by DiGangi and Hefner
(Chapter 5). As with sex assessment from the pelvis, current studies have been quantifying
the visually assessed dimorphic traits of the skull ( Rogers and Saunders, 1994; Konigsberg
5 The younger age of this range approximates when masculine traits appear in adult males and the later age
approximates when masculinization of the skull begins in females after menopause.
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