Archaeologists use tooth enamel protein to show sex of human remains
New method used in Bay Area excavation

Date:
July 20, 2020
Source:
University of California - Davis
Summary:
A new method for estimating the biological sex of human remains
based on reading protein sequences rather than DNA has been
used to study an archaeological site in Northern California. The
protein-based technique gave superior results to DNA analysis in
studying 55 sets of human remains between 300 and 2,300 years old.



FULL STORY ==========================================================================
A new method for estimating the biological sex of human remains based
on reading protein sequences rather than DNA has been used to study an archaeological site in Northern California. The protein-based technique
gave superior results to DNA analysis in studying 55 sets of human
remains between 300 and 2,300 years old. The work is published July 17
in Scientific Reports.


==========================================================================
The method targets amelogenin, a protein found in tooth enamel, said first author Tammy Buonasera, postdoctoral researcher working with Glendon
Parker, adjunct associate professor in the Department of Environmental Toxicology at the University of California, Davis. The technique was
developed in Parker's laboratory.

Buonasera, Parker, Jelmer Eerkens, professor of anthropology,
and colleagues compared three methods for sex determination: the new
proteomic method; DNA analysis; and osteology, or analysis of the size,
shape and composition of the bones themselves. They applied these methods
to remains from two ancestral Ohlone villages near Sunol, California. The
site is being excavated by the Far West Anthropological Research Group
of Davis in collaboration with the Muwekma Ohlone tribe.

Amelogenin is a protein found in tooth enamel, the hardest and most
durable substance in the human body. The gene for amelogenin happens
to be located on both the X and Y sex chromosomes, and the amelogenin-Y
protein is slightly different from amelogenin-X.

The method works by retrieving a tiny amount of protein from a tooth. All proteins are made up of a chain of amino acids, so the protein is analyzed
to give the amino acid sequence, which then defines the protein. Each of
the 20 naturally occurring amino acids is specified by a three-letter
code in DNA, so it is possible to work backward from the amino acid
sequence and figure out the likely DNA code.

Superior to existing methods The researchers were able to determine
the sex of all of the remains using the new protein method and all but
five using DNA methods. Results from osteology and proteomics agreed in
almost all cases, although examining bones themselves was only effective
for about half the skeletons.

The protein method allowed them to estimate sex for children, which is
not possible from osteology. It was reliable even when the signal from
DNA was weak.

"This is a more sensitive technique for older skeletons where we would
expect more DNA degradation," Parker said.

Being able to determine the biological sex of human remains provides
a greater window into the persona of each individual. Anthropologists
are interested in determining biological sex because sex interacts with
health and can have a large impact on how people form an identity and
are treated within a society, Eerkens said.

"Almost every human society around the world incorporates sex and gender
as a way to classify people, and these can affect your status and who
you associate with in society," Eerkens said. While gender and biological
sex are not the same thing, they are linked, so the ability to estimate
sex gives archaeologists important insight when attempting to understand
the cultural aspects of gender, which are not as readily preserved.

For example, in a society based on small villages, people often have to
find mates outside their village. Depending on cultural rules, either
men or women will leave the village to marry.


========================================================================== Story Source: Materials provided by
University_of_California_-_Davis. Original written by Andy Fell. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Tammy Buonasera, Jelmer Eerkens, Alida de Flamingh, Laurel Engbring,
Julia Yip, Hongjie Li, Randall Haas, Diane DiGiuseppe, Dave Grant,
Michelle Salemi, Charlene Nijmeh, Monica Arellano, Alan Leventhal,
Brett Phinney, Brian F. Byrd, Ripan S. Malhi, Glendon Parker. A
comparison of proteomic, genomic, and osteological methods of
archaeological sex estimation. Scientific Reports, 2020; 10 (1)
DOI: 10.1038/s41598-020- 68550-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200720093300.htm

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