Clues to How Homo sapiens Conquered Earth Emerge from Digs in South Africa [Slide Show]
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At PP5-6, an excavator works in sediments that date to about 74,000 years ago, right at the contact between the glacial and the interglacial periods. Image: Curtis Marean
All sediments are sieved through a set of nested screens to catch any archaeological finds that were too small for the excavators to see. Image: Curtis Marean
The sediments are dried and then carried up to the site for packing, and then transported to the laboratory for sorting. Image: Curtis Marean
All finds are placed into small baggies that have a bar code label attached. That label is a unique specimen number identifier. Image: Curtis Marean
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All finds are measured to millimeter accuracy with a total station, an electronic device that allows archaeologists to map the positions of the artifacts they uncover. Theta is the yellow survey device seen at the upper left... Image: Curtis Marean
The upper portion of PP5-6 dates roughly from about 60,000 to 50,000 years ago. Excavators carefully removing sediment while gunners (those operating the total stations) continually measure the finds... Image: Curtis Marean
Recorders handle the data, entering all field observations into tablet computers ( right ). The only use of paper on site is for the bar-code labels, which the recorder affixes to the bags ( left )... Image: Curtis Marean
Long ago tool makers on Africa’s southern coast made their small projectile points from a stone called silcrete. To improve the quality of the stone they subjected it to heat treatment before knapping it... Image: Curtis Marean
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The team employs the same high-resolution field procedures at the open-air site of Vleesbaai. A gunner runs the total station (left, background) while an excavator patiently reveals artifacts (right, foreground)... Image: Curtis Marean
Today the site of Vleesbaai is directly on the sea, but when early H. sapiens occupied it, the coastline must have been far away because it dates to the time of a glacial when sea levels were much lower. The ancient occupants of Vleesbaai would have looked out onto a rolling plain filled with migratory animals... Image: Jayne Wilkins
Excavators reveal middle stone age artifacts on a land surface at Vleesbaai that dates to around 70,000 years ago. The red sediment is a paleosol (ancient soil) and a dune is stratified above. Image: Jayne Wilkins
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