What are the key achievements and contributions of roman civilisation ?

The belief that war often drives civil modifications to a society is based upon the evidence that in times of external conflict, a society is forced to abandon long held discriminatory values to:

Prior to the presence of europeans on the continent, the slave trade in africa a) did not exist in any form. b) was limited to internal trade only. c) included the trans-saharan and indian ocean slave trade. d) was rarely needed due to the lack of an agricultural economy.

West africans received salt from who?