As you report, Lyn Wadley of the University of Witwaterstand and her colleagues have discovered something like mattresses in a natural rock shelter called Sibudu in South Africa (“A Place to Rest Your Weary Head,” December 10, 2011). Made of several layers of leaves, some of which have insecticidal properties, they date from more than seventy-thousand years ago. As you point out, the mattresses provide another piece of evidence of sophisticated artefacts from this period. However, you fail to mention, even in passing, the best piece of evidence of rapid human development from the same period and roughly from the same place. The Blombos Cave in South Africa revealed a decade ago the first piece of art discovered to date. A piece of ochre decorated with geometric patterns, it is executed with aplomb. For all their comforts, the mattresses surely take the second place to the Blombos find when it comes to our ancestors’ growing sophistication.