There are many scientific limitations to the home DNA test. “These companies aren’t actually testing your ancestry at all,” says Mark Thomas, professor of evolutionary genetics at University College London. “They’re problematic in their claims to be able to infer an individual’s ancestry.”
There are a few reasons for this. First, the genetic information these DNA testing companies hold is based on living populations. When you send your spit off in a little tube, it is specific snippets, or markers, in your genome (the total collection of DNA that resides in your cells) that are being analysed, and then compared to the markers of others who are good representatives for distinct regions or ethnicities around the world. But as Thomas notes, the companies are only looking at very recent samples, from a relatively small group, in one specific database. “They are just saying: ‘If I wanted to make your genome, I could pull bits of your DNA from people all over the world who are around today. And this is just one way I could do it,’” he says.
