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Bridget Algee-Hewitt of Stanford UniversitySkeletal remains laid bare by the elements are a difficulty for death investigations. A vital first step is to determine the ancestry of the deceased. Often this is done with measuring the skull’s shape and size.

There’s just one problem – and it’s a growing problem. In a diverse melting pot of genes like the United States, fewer people than ever before are from one ethnic group. Even those who identify as black or white may have a complex DNA palette producing unique body dimensions – including skull shape and size.

Craniometrics is an anthropological discipline where measurements of the skull are used to determine someone’s ancestry. It can be very accurate with people from one genetic background – but the more mixed ancestry there is, the less reliable it becomes.

A recent paper proposes to revamp the skull-measuring discipline, to bring it in line with the most recent DNA analysis instead of self-reported ethnic background. By bridging the gap between forensic anthropology and forensic genetics, Bridget Algee-Hewitt proposes to do no less than to “bring craniometrics up to the data gold standard of DNA,” as she explained in a recent interview.

“Genetics has taken the whole question of ancestry up to a completely different level,” Algee-Hewitt told Forensic Magazine. “We now have standards and methods that are very refined in genetics that we need to start applying to craniometrics so that we have compared analyses and comparable data returns.”

Algee-Hewitt, currently of Stanford University, published the paper in February in The American Journal of Physical Anthropology fusing her two backgrounds: traditional anthropology with the data-heavy DNA analysis of large populations.

By combining craniometry with the latest genetics, people can be better identified, and crimes can be solved.

“There’s always been this uncomfortable positions as a skeletal person versus a DNA person, because you have two different data types and they each go away and do their analysis. Doing two completely different things,” she said. “This is bridging a gap that has a long history of being a gap.”

Questions We Never Knew to Ask

DNA science has reached a point where it’s telling us more than we ever knew before about biology – while also raising more questions we never knew to ask.

Once a person was classified simply as “white or “black” or “Asian” or “Native American.” But now the percentages of each racial group we acquire over generations has made genetic portraits much, much more complex. Even medicine has begun a major shift as the effectiveness of drugs and medical interventions has become intertwined with a person’s DNA.

What has caused that shift in personalized medicine and genomics, has revolutionized forensic identification.

Noah Rosenberg, head of the Rosenberg lab at Stanford University where Algee-Hewitt has worked since 2013, said biometrics can be linked to genetics, with enough information from enough individuals.

“If data are available on enough sites in the genome, we have known for a while that people can be probabilistically placed into clusters that provide detailed information about their genetic ancestry. If biometric traits that have at least a partial basis in genetics are considered, it stands to reason that with similar methods, a similar result would also hold,” said Rosenberg. “Adapting population assignment methods from genetics can be informative in forensic anthropology. The methods accommodate individuals who do not fit neatly into predefined population categories.”

'Letting Data Paint the Picture'

A prime example of the current difficulties with racial classification is the category currently known as “Hispanic.” Nearly impossibly complex, its diversity is shown perhaps most acutely at the unfolding tragedy of bodies found at the U.S.-Mexico border. “Hispanic” is really a catch-all term that groups together wildly diverse groups of Mexicans, Guatemalans, South Americans of dozens of nations and ethnic groups. Identifying them and trying to notify their next of kin back home has been a humanitarian crisis. Algee-Hewitt’s methodology incorporated a cross-section of those bodies into her latest study.

But the United States population itself has a pronounced set of difficulties. A massive study of 23andMe data published last year in the American Journal of Human Genetics by Harvard University researchers showed that the degree of mixture is greater than had been believed.

READ MORE: Does CODIS Contain Untapped Ancestry Information?

Algee-Hewitt points to that study and says her method of skeletal-genetic analysis is a close match – and bound to improve. 

“My estimates correspond very closely to theirs,” she said.

The next step for the work is to take the mathematical models and make them more comprehensive with thousands more cross-referenced samples. The equations and methodology are all open-source. This could be used in tandem, or even potentially as an alternative to FORDISC, the biometric identification program developed by two University of Tennessee scientists in the 1980s.

Algee-Hewitt completed her doctorate at the University of Tennessee. Later this year she is assuming an assistant professorship in the Department of Anthropology at Florida State University, where she will teach, continue with forensic case work, and researching better skeletal analysis involving laser scans.

But mixing anthropology with DNA is “only going to get more complicated” – and accurate in her work, she said.

One advantage is it starts out with just the data – none of the presuppositions of ancestry and race,” she said. “You’re just letting the data paint the picture.”

 

 

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