33 – Heat treatment of raw materials (stone tools and ochre)

162,000 years ago

The discovery of heat-treated and flaked stone tools in southern Africa dating to around 70,000 years ago indicates that humans’ ability to solve complex problems and may have occurred at the same time their modern genetic lineage were taking advantage of abundant and predictable marine food resources along the coast. Stones called silcrete, which are soft, had to be heat treated to harden them for flint knapping. If stones are heated too long, they are brittle; if they are not heated enough, they do not break sharply. This long-chain thought process shows that early modern humans living in caves at the southernmost point of Africa were able to replicate this process and possibly teach it to others in their group.

Image credit Simen Oestmo.


    Pleistocene2.58 million to 11,700 years ago

Environmental and Climate Changes

  • Earth’s climate remains relatively stable with alternating glacial and interglacial periods

Changing Species