Mixed Race Studies

The pitfalls of tracing your ancestry

Nature News
Nature Magazine
2008-11-13

Brendan Maher

Charmaine Royal of the Duke Institute for Genome Sciences and Policy explains the limitations of genetic testing.

Ancestry testing is genetics’ most direct and sometimes tempestuous interaction with personal identity. An estimated half-a-million Americans will purchase genetic tests from companies this year and thousands more will participate in university research where such tests will be used. The tests raise ethical and legal questions, on which an 11–15 November meeting of the American Society of Human Genetics (ASHG) in Philadelphia, Pennsylvania, hopes to provide some guidance.

Charmaine Royal, an associate professor at the Duke Institute for Genome Sciences and Policy in Durham, North Carolina, who co-chairs a task force—looking at genetic ancestry testing—at the meeting, talks to Nature.

What prompted the ASHG to develop these recommendations?

People have been researching their ancestry forever, using stories and historical records, and people have taken advantage of genetic technology with the hope of learning more. But there’s this perspective that genetics provides the truth, and that may need to be challenged. In general, genetic ancestry testing is fallible just like many of the tools we use. Some people think that genetics will provide the be all and end all of information about their ancestry. There are limitations as to what ancestry can provide…

…What are the limitations of such tests?

The general limitation, I’d say, of all of these tests, is that they can’t pinpoint with 100% accuracy who your ancestors may or may not be. Some people are concerned that the biogeographical ancestry test reifies the notion of race. This is the notion that there are four or five parental groups from which we all came and there are discrete boundaries between these groups. But our genetic research has shown that those boundaries don’t exist.

In lineage testing, where someone is wanting to know which tribe or region in Africa they came from, the information that’s given is based on the present day populations. The names of those groups and those locations have changed over time and so people getting that information about present day Africans and extrapolating to who their pre-middle-passage ancestors may have been—that may not necessarily be accurate. So, those limitations need to be clarified.

Another limitation is that the outcomes of ancestry tests are very much dependent on what is already in a database—who a client’s DNA can be matched to. If a database is not comprehensive some potential matches will be missing, and nobody has a complete database. That’s a major limitation, probably one of the biggest…

Read the entire article here.