Biology Reference
In-Depth Information
discussed more by McKeown and Schmidt (Chapter 12), this volume. Sex estimation using
craniometrics from the Forensic Databank is available through the program FORDISC 3.1
(Ousley and Jantz, 2012). DiGangi and Hefner discuss FORDISC in more detail in the chapter
on ancestry estimation in this volume (Chapter 5). Similar to visual methods of assessment
discussed earlier, population specificity is equally important for craniometric studies.
Ribs and Vertebrae
For the most part, ribs have played a more central role in age estimation than sex estima-
tion (refer to Uhl [Chapter 3], this volume). One study by
I¸can and Loth (1986)
demon-
strated that the sternal rib ends do exhibit sexual dimorphism. This study used
discriminant function analysis to compare the perpendicular measures of maximum supe-
rior
posterior breadth of the fourth sternal rib end
in individuals with a rib phase between stages 1 and 7 (i.e., approximately 14
e
inferior height and maximum anterior
e
70 years).
The average accuracy rate was 83% and the method worked better for females than for
males. However, this method did not work for adults who were very young or very old
(
I¸can and Loth, 1986
).
The vertebrae exhibit sexual dimorphism in size even before puberty. The developmental
significance of this early sexual dimorphism is unknown, but this could be the result of either
intrinsic hormone levels or extrinsic variables of population specific activity and/or body
mass (
Gilsanz et al., 1997
). Male vertebrae are larger, especially the lumbar vertebrae. This
study is discussed in further detail below under subadult sex estimation (
Gilsanz et al.,
1997
). The atlas is significantly greater in breadth in males (
Brothwell, 1963
). A metric anal-
ysis of eight measurements of the articular surfaces and vertebral foramen area on the atlas
provided sex estimation accuracy between 75% and 85% (
Marino, 1995
).
e
Sex Estimation: The Appendicular Skeleton
Upper Limb
SHOULDER GIRDLE
The upper arm and shoulder girdle may be one of the most sexually dimorphic areas of the
skeleton (even better than the pelvis, see below), which is evident by the high rates of clas-
sification for the humerus, clavicle, and scapula. From the review of previous literature on
sex estimation for this chapter, the highest single variable success rate was achieved from
the humeral head diameter. This study by
Frutos (2005)
achieved 96% accuracy from univar-
iate sexing of the humeral head diameter. This may be due to functional differences between
males and females in population-specific behaviors, as well as intrinsic hormones that affect
the bones and musculature of this region.
As previously discussed,
Spradley and Jantz (2011)
compared all of the cranial and
postcranial elements from the Forensic Databank for sexing accuracy rates to create a hier-
archy of effectiveness. The rankings of their univariate analysis with sexing accuracy rates
for the upper limb were (1) scapula height (87%), (2) humeral head (86%), and (3) scapula
width (86%). Multivariate discriminant function analysis from these measurements was
able to achieve higher discrimination rates, up to 94%. The maximum length of the clav-
icle also shows high levels of sexual dimorphism with classification accuracy rates at 85%
