One of several DNA test kits available to the public. Their infographics and pie charts make for great family conversations, but they are far from being precise census documents. (Eric Baradat/AFP/Getty Images)

What’s often missing from conversations about ancestry was pointed out clearly in the Nov. 6 Health & Science article “Are DNA tests more art than science?”: “Your DNA, in short, is matched up with living people in those regions, not with your ancestors from those places.”

An instructive example is Ötzi the Iceman, the well-preserved natural mummy of a man who lived between 3400 and 3100 B.C. and was discovered by hikers in 1991 on a 10,000-foot glacier on the border between Austria and Italy in the Ötztal Alps (thus, “Ötzi”).

DNA analysis revealed that genetically, Ötzi was not like most of today’s Italians or Austrians or even Eastern Europeans. His closest living relatives can be found in Sardinia in the Mediterranean Sea. This does not mean Ötzi was Sardinian. More likely: When he was born, most people in Europe, including Sardinians, carried similar DNA patterns. But while Europe experienced centuries of migrations, southward from Scandinavia and westward from Asia, the population in more isolated Sardinia remained stable and thus relatively unchanged genetically.

George Diffenbaucher, Alexandria