Biology Reference
In-Depth Information
When preparing to extract DNA from teeth or to present materials to a lab for analysis
(refer to Cabana et al. [Chapter 16], this volume, for information on sampling techniques),
the molars are the best teeth to begin with due to their size (more material to sample) and
relatively protected location within the oral cavity. Standard practice holds that harvesting
DNA from the teeth is most fruitful from the dentin and dental pulp within the pulp
chamber (
Herschaft et al., 2007
). As this area is the most protected from the outside world,
contamination is less likely and the material is most often undisturbed. Barring the presence
of dental pulp, the next best places to harvest from are the dentin and cementum (
Herschaft
et al., 2007
). However, a recent study by Adler and colleagues (2011) found that the mtDNA
content in dental cementumwas up to five times higher than that present in the dentin, indi-
cating that extraction from the root might also be a productive strategy.
ISOTOPE ANALYSIS
Isotope analysis is useful in forensic, bioarchaeological, and paleontological contexts.
Teeth are the single most abundant element in the fossil record due to the relative durability
of enamel. Tooth enamel is less susceptible to diagenesis, the process of chemical change and
decay in organic remains following death, so isotopic evidence from teeth has the potential to
produce more reliable results than can be obtained from bone. Because the mineralized
portions of teeth are 20
e
25% higher than that of bone, they may very well provide a more
faithful representation of the acquisition and integration of isotopes into body tissues during
life. As with other elements of the skeleton, the most frequently studied isotopes in teeth
include carbon, nitrogen, and strontium, which reveal information about diet (carbon,
nitrogen) and geographic location (strontium).
The permanent teeth begin development while in utero and generally complete develop-
ment in the late teenage years (with the exception of the variable third molar). Also, unlike
bone, teeth do not remodel during life. Therefore, there is a somewhat truncated window
for the uptake of isotopes into the teeth in relation to the rest of the skeleton. For a discussion
of how this occurs, refer to Bethard (Chapter 15), this volume. As a result, analysis of isotope
ratios in dental material is likely to reveal very good information about the early life of an
individual, even providing information about diet surrounding the timing of weaning
(
Wright and Schwarcz, 1998
). But although isotopic information from the teeth is particularly
useful in regard to the area where individuals were born and spent their early years, it will
not reflect changes in diet and environment that may have taken place later in life. However,
isotope ratios in bone can reflect changes in diet and location as ratios turn over in bone
roughly every ten years. For more detailed information on isotopic analysis, see Bethard
(Chapter 15), this volume.
As an example, Sealey and colleagues (1995) studied the remains of five individuals from
different temporal contexts and life situations from South Africa including two prehistoric
Khoisan hunter
e
gatherers, two likely European soldiers, and a female in her fifties buried
beneath the floor of a lodge where enslaved persons lived. Sealey and colleagues analyzed
the isotopic ratios present in an earlier forming tooth (the first permanent molar or an
incisor), the third permanent molar (which is the last tooth to form), and a sample from
the skeleton, which as discussed above would have turned over within the ten years or so
