Researchers develop new method to determine biological sex of human skeletal remains
SACRAMENTO, Calif., U.S.: Through science, our ability to decode the past has continued to improve. In another advancement that will help archaeologists better understand ancient societies and peoples, researchers from the University of California, Davis (UC Davis) have developed a method to estimate the biological sex of human skeletal remains based on protein traces in teeth.
Because amelogenin proteins play a role in the formation of tooth enamel, and the genes for amelogenins are located on the X and Y chromosomes, the team used sensitive mass spectrometry to measure proteins in teeth. The new method was developed by Dr. Glendon Parker, assistant adjunct professor in the UC Davis Department of Environmental Toxicology, along with Julia Yip, a student in the UC Davis graduate program in forensic sciences, Director of the UC Davis Proteomics Core facility Dr. Brett Phinney, Professor of Anthropology Jelmer Eerkens and colleagues.
“Wear patterns on the tooth can tell us about diet. Morphology of the tooth can tell us about ancestry - different populations around the world have slight variations in the shape of teeth. Plaque adhering to the tooth can tell us about bacteria in the person’s mouth, including pathogenic bacteria. We can radiocarbon date the tooth to learn how old it is. And stable isotope data can tell us about how a person traveled across the landscape,” said Eerkens.
As part of the process, Yip looked at 40 enamel samples of permanent teeth and primary teeth from 25 individuals. The samples were from the modern era and 100–7,300 BP and were collected from archaeological sites in North America and Peru. Since females have an amelogenin-X in their teeth, males should therefore have both the X and Y versions of the protein. Yip found traces of amelogenin-X in all the samples and amelogenin-Y in about half of them.
However, because amelogenin-Y is usually at lower levels than amelogenin-X, a tooth that tested negative for amelogenin-Y could be a false negative if there was just too little of the Y form to detect. To overcome this, the researchers developed a statistical method to work out the probability of such false negatives given a certain amount of amelogenin-X.
Noting that the new method would most likely be used alongside existing techniques, Parker said, “Like DNA our method is quantitative and does not depend on anatomical training, it is cheaper to run per sample (than DNA) and can be done in non-sterile conditions.”
The study, titled “Sex estimation using sexually dimorphic amelogenin protein fragments in human enamel,” was published online in the Journal of Archaeological Science on Nov. 9, 2018, ahead of inclusion in an issue.
Tags: biological, history, identification, teeth