On Saturday the AP wire carried a startling story, by Matt Crenson, that at first glance seems nonsensical. The idea is that, when one runs the mathematics of genaeologies and the populations growth and migrations of humanity, everybody alive today has at least one common ancestor in the fairly recent past. The most recent such mega-grandpa or grandma almost surely lived 2000-5000 years ago, according to scholars he cites. It says here that it might have been when the pyramids of Egypt were rising, or when the Han Dynasty united China. Seems ridiculous. It means that nowhere in Australia is there an aborigine with pure ancestry dating from that continent’s near-isolation after the first people arrived there tens of thousands of years ago, no similarly isolated people in New Guinea or the Amazon. But Oxford University and MIT statisticians say that the numbers are convincing. Still, so many questions arise. The Tracker, who recognizes that this line of thought is not new, would like to have asked Crenson’s sources whether they are sure there are no isolated populations whose last mixing with the greater genome was longer ago than the numbers cited here. And, given the re-sorting of genes with each generation, is it a lock that at least one gene from this last putative common ancestor remains in all people now? The wire sent the story with the hed, “Roots of Human Family Tree Are Shallow.” That is surely misleading. We may have a few shallow roots, sure. But more important, we also have deep ones that go back, back, back….

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