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In This Issue

Fossil analysis, especially the assessment of dental growth, can provide insight into modern human development. Tanya Smith et al. report that developmentally modern humans existed at least 160,000 years ago, and evidence in the form of incremental features formed during tooth growth could push back the date that Homo sapiens began living in North Africa. Smith et al. studied the growth patterns of a fossilized, juvenile tooth found in Morocco. Because of rhythmic changes that take place during tooth growth over hours, days, and years, the speed and duration of development is permanently recorded in each tooth. The 7.8-yearold juvenile displayed characteristics similar to modern Europeans, including an equivalent degree of tooth development as a similarly aged European child. Compared with other hominin teeth, this individual’s growth patterns were more similar to modern Homo sapiens than to other Homo species. Based on the correlation between dental development and other life history events, Smith et al. suggest that this individual would have had a similarly long developmental period and childhood. The results may help us understand when and where modern human anatomy and behavior originated, including the relatively long childhood observed in modern humans. — P.D.