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Marcus is proud of his African American heritage. He has done a lot of reading on the slave trade and the peoples of west Africa that were brought to the Americas. Marcus is familiar with the genetic tests marketed to measure African ancestry, and had already considered taking one of these tests himself. This interest in his African ancestry is what motivated Marcus to sign up for a first-year college seminar course that provided an opportunity to obtain genetic test results from 23andMe. Marcus didn’t hesitate when it was time to spit into the tube and send off for a DNA test. He thought that the results would shed some light on where is Africa his ancestors had come from. After a month when Marcus’ test results were available on the 23andMe website, he was shocked with the report on his Ancestry Composition. It reported 80% Sub-Saharan African ancestry mostly attributed to West Africa, but it also estimated 17% European and 2% East Asian & Native American ancestry. Marcus was stunned, because he wasn’t aware of any family members with mixed ancestry.


Should it be shocking to Marcus that his test results indicate mixed ancestry?

Marcus’ results estimated both European and East & Asian & Native American history, does this mean that more than one mixed relationship has occurred since Marcus’ ancestors arrived in the Americas?

What is your own ancestry, and how unsettling would it be to find that your Ancestry Composition is more mixed than you currently envision?


The news of Marcus’ mixed ancestry was quite unsettling to him. At the end of the semester, based on what Marcus had learned in the course he investigated other testing companies to obtain a different measure of his ancestry that he thought would be more accurate. When he got the results back, however, the results did not agree at all with the 23andMe analysis. The new test estimated lower African and European percentages, and this time included 6% Mediterranean composition. Marcus considered the results of both tests bogus and lost all faith and interest in genetic analyses of ancestry.

Is it surprising that the ancestry composition estimated by two different companies would not be exactly the same?

Is it reasonable to think that a person has an ancestry that traces to a single place?

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