1.   Bows and arrows were used by prehistoric humans to hunt for food.

2.   He exposed more pieces of wood from the camp where prehistoric humans once lived.

3.   Prehistoric humans liked to take shelter under overhanging rocks like that.

4.   The movie has prehistoric humans, too.

5.   In the cool twilight of a cave once home to prehistoric humans, biologist Stephen Weiner ran a sediment sample the size of a pinhead through an infrared spectrometer.