A further challenge to the notion of a cognitive revolution is recent evidence that Homo sapiens were capable of symbolic behavior a long time before modern humans spread out of Africa. Most striking is a recent study based on excavations at a dried-up lake bed in Olorgesailie, Kenya.[26] Archeologists found lumps of rock that appeared to have been processed to create pigments over 300,000 years ago: manganese ore, ground down to produce black or dark-brown coloring, and iron-rich minerals that were used to make ocher. The ocher rocks did not come from the nearest source, which suggests that
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