Anthro Notes – Oct. 25/12
- Traditionally, as summarized in 1988 by Iscan, forensic anthropology focused on reconstructing
osteobiographies (aging, sexing, stature, ethnicity). The new forensic anthropology as outlined by
Dirkmatt et al emphasizes both lab and field skills. The changes in admissibility and the influence of
DNA have changed the landscape of forensic anthropology. Some researchers have suggested that
with the advent of DNA testing, individuation of skeletal remains has been replaced. We countered
that by noting several important contributions individuation still makes to forensic science. Also
Dirkmatt et al mention the development of improved quantitative methods from modern databases
like the FDB (Fordisc). The Fordisc program uses multivariate statistics based on the FDB to estimate
stature (osteometrics of long bones) and sex and ancestry (based on craniometrics).
- Forensic anthropology – individuation and DNA analysis: Is individuating skeletal remains still
relevant in the age of DNA? There are a number of reasons why doing an osteobiography is still
relevant – 1. DNA may not always be preserved and even if it is, there could be allelic dropout. 2.
Nuclear and mitochondrial DNA can build a genetic profile, but it cannot build a biological profile. A
biological profile is used to reduce the potential matches so that a reasonable number of comparative
genetic samples can be obtained. 3. The differences between the biological and genetic profile are
particularly important when comparative DNA is lacking. 4. In situations of commingles remains, the
anthropologists can associate parts of the skeleton to make the expensive DNA processing more
efficient. 5. All data are circumstantial so as much information as possible can help solve cases. Even
class traits can narrow down the list of suspects.
- Sequence of questions addressed by a forensic anthropologist: 1. Are the remains human? 2. Are the
remains of forensic or archaeological interest? 3. Is there more than one individual? 4. When did the
death occur? 5. How old was the decedent? 6. What sex was the decedent? 7, How tall was the
decedent? 8. What is the population affiliation (race) of the decedent? 9. Are there any idiosyncratic
data (anomalies) to help with individuation?
- Procedures in the analysis of skeletal remains: Inventory (number of individuals). Age estimate. Sex
determination. Morphology (measurements and osteoscopic traits for population affiliation). Note
presence of pathologies that could be useful for individuation or assist in cause of death
determination (fractures such as the hyoid bone can be useful in addressing cause of death, but the
coroner or pathologist has this responsibility). Calibration of osteometric equipment and standards
for osteoscopic traits. Do blind analysis – give key elements a random number and later assess the fit
between the methods.
- Craniometry involves measurements of the skull. There are over 200 nonmetric osteoscopic traits
that are studied by bioanthropologists. Some occipital bones have an accessory bone called os inca,
which was first discovered among inca skeletons. Some zygomatic bones have an accessory bone
called os japonicum as it was first analyzed in Japanese crania.
- Aging skeletons: Age changes vary between and within populations. Sex differences are the biggest
intra-population variant. Different methods are used for aging subadults and adults. All age estimates
have a standard deviation which is larger the older the person. At certain ages, some methods are
more accurate than others (teeth are best for young people).
- Types of methods: Osteometric analysis – measuring bones with calipers. Ossification – as skeletons
develop, centres of ossification appear, grow, and unite in adulthood. Morphogenesis of certain
regions – age changes occur in regions like the sternal rib ends and the face of the symphysis pubis.
Histological changes occur in bone and teeth. Teeth undergo calcification and eruption. Degenerative
changes occur in the skeleton and teeth (attrition/wearing down). Forensic odontologists and forensic anthropologists are both skilled in the aging of unknowns from dental eruption and
- Key aging markers for human skeletons: Measuring the basioccipital in the fetus and the long bones
in infants and children is used. Dental calcification (more important) and dental eruption is used for
aging infants and children. Dental calcification (3 molar) is also used somewhat for aging
adolescents. Ossification is important in aging adolescents and young adults (18-35) and somewhat
important in aging fetuses, infants, and children. The symphisis pubis is important in aging young
adults and somewhat important in aging adults (36-50). Ribs are important in aging young adults,
adults, and older adults (50+). Histology is important in aging young adults and less important in
aging adults and older adults.
- Occipital bone: At birth, the occipital bone is in several parts. The base is measured in fetuses and
neonates as a means of age estimation. Measurements or osteometrics of the basi-occiput are best for
- Aging subadults (birth-12 years): Ranking of methods – 1. Dental calcification and eruption. 2. Fusion
of bones. 3. Size and proportion of long bones.
- Stages in the development of human dentition: Dental calcification and eruption provide forensic
anthropologists with a fairly accurate (lower standard deviation) method of estimating age at death
of immature human remains. The standard deviation for age estimates gets higher as one moves
from early to late childhood.
- Primary and secondary centres of ossification using long bone model: Cartilaginous model of a long
bone. 1st primary centre in diaphysis. 1st secondary centre in distal epiphysis of this bone. 2nd
secondary centre in proximal epiphysis. 2nd secondary fuses first. 1st secondary centre fuses last.
This ends growth of the long bone. Growth and development are longest and strongest in the
shoulder, wrist, and knee. The epiphysis is the rounded end of a long bone, at its joint with adjacent
bones. So it goes proximal epiphysis, diaphysis, distal epiphysis.
- Aging adolescent skeletons: The union of epiphyses (secondary centres) is quite variable with
females in a given population and it precedes males by 1-2 years. Some epiphyses fuse in early
adulthood, such as the medial end of the clavicle, the iliac crest, and the sacrum. The spheno-occipital
synchondrosis in the skull fuses between the ages of 13 and 22 years. Synchondrosis is a plate of
cartilage that fuses, and this particular synchondrosis is the cartilaginous junction between the
sphenoid and occipital bones in the skull.
- Aging adult skeletons: The fusion of key skeletal elements can be used to age younger adults (20-30
years), for example iliac crest fusion, the medial clavicle, and S1-S2. The metamorphoses of the
symphysis pubis of the hip and the sternal end of the ribs can be used for aging. Different standards
are applied to males and females. The fusion of the medial clavicle, the iliac crest, and the sacral
vertebrae S1 and S2 happens in the mid to late 20s. A skeleton with these areas fused is generally
considered to be about 30 ± 5 years.
- Aging using rib and symphysis pubis methods: Sex has to be determined first since males and females
have very different patterns. Age always has a standard deviation which is greater with increasing
age. It is best to use as many methods as possible.
- The symphysis pubis changes with age. The symphyseal face in a younger person has well-defined
ridges and furrows that fill in with age. The symphysis pubis is rough in young adults and smooth in
old adults. Also, the ventral margin in younger people is sharp and at right angles with the pubic face.
As bone fills in, it forms a ventral rampart (wall/barrier). A dorsal plateau and rim on the symphyseal
face also develop as people age.
- Age estimates for males and females using Suchey-Brooks method: The standard deviation and 95%
confidence interval range increase a lot the older the person is. It becomes increasingly unreliable
after 30 years. Interobserver reliability is very poor. Females have larger standard deviations than males and this is probably due to birth trauma. We have to be cautious when aging older people
because of the unreliability, and so it is best to use many different methods.
- The sternal rib (usually the 3 , 4 , or 5 ) changes with age. There is sharpness of the rim, scalloping
the rim, projections from the rim, pit formation, and brittleness. Rib age estimates using the Loth-
Iscan method look at rib morphogenesis, and this method is recommended for older adults over the
symphysis pubis method since it usually has a smaller standard deviation.
- Other methods for aging adults: Dental attrition is used as part of the Gustafson method. Dental
attrition is probably the most reliable method, although it is subject to dietary patterns. Degenerative
joint disease can be used for aging. Histological age can be used for aging (the number of osteons
increase with age). C14 levels in enamel can also be used.
- Gustafson method of aging adult teeth: This method looks at the rates of dental attrition, secondary
dentin, paradentin, cementum apposition, root transparency, and root resorption. As attrition occurs,
dentin becomes exposed. Recent testing of this method shows low reliability in some populations.
Dental attrition is normal wear of teeth from mastication and it is age related and population specific.
Standards of dental attrition are developed with reference to other methods. Generally, the older the
person, the more dentin exposure. The first molar comes in around 6-7 years. As you get older, there
is more wear and therefore more dentin exposure, on M1.
- Histological structure of bone: Forensic anthropologists must know bone histology because it is
useful in age estimation. As we grow, the number of haversian systems (circular systems) increases
and they are remodeled. Lamellar bone is organized in haversian systems. Computer software
analyzes the number of existing and remodeled haversian systems and compares them to a stand