The discovery of the blombos cave suggests .copper alloy or bronze casting were first used in sub saharan africa.
b. islam became an economic and religious force in west and north africa.
c. that abstract thought in humans occurred much earlier than once thought.
d. the french colonies were taken over before the third or fourth centuries.

The correct answer is letter C, that abstract thought in humans occurred much earlier than once thought. This excavations were very important because they gave new and important information about the behavioral evolution of modern humans. The innovations that humans once made were excavated from these archaeological finds giving people more knowledge how we have evolved.

the longest time is 123 years