ST LOUIS, MISSOURI—A new study of early human fossils concludes that they exhibit a high frequency of congenital abnormalities, perhaps indicating that Pleistocene populations were small and isolated. As an example, fragments of a 100,000-year-old skull unearthed in northern China show evidence of a disorder known as “enlarged parietal foramen,” caused by a genetic mutation that is rare in current populations. “It remains unclear, and probably un-testable, to what extent these populations were inbred,” noted the study, which was led by Erik Trinkhaus of Washington University in St. Louis.