. ▁Arch ae olog ists ▁have ▁found ▁that ▁evidence ▁of ▁trade ▁in ▁lux ury ▁items ▁like ▁met als ▁and ▁shell s ▁across ▁the ▁entire ty ▁of ▁the ▁continent ▁were ▁the ▁main ▁tr ades ▁of ▁the ▁Ber ber ▁people , ▁lived ▁in ▁dry ▁areas ▁and ▁became ▁nom adic ▁her ders , ▁while ▁in ▁the ▁sav ann ah ▁grass lands , ▁cultiv ated ▁cro ps ▁and ▁thus ▁permanent ▁settlement ▁were ▁possible . ▁Agricult ure ▁supported ▁large ▁towns , ▁and ▁eventually ▁large ▁trade ▁networks ▁developed ▁between ▁the ▁towns . ▁ ▁Orig ins ▁of ▁agricult ure ▁The ▁first ▁agricult ure ▁in ▁Africa ▁began ▁in ▁the ▁heart ▁of ▁the ▁Sah ara ▁Des ert , ▁which ▁in ▁ 5 2 0 0 ▁BC ▁was ▁far ▁more ▁mo ist ▁and ▁dens ely ▁populated ▁than ▁today . ▁Several ▁native ▁species ▁were ▁domestic ated , ▁most ▁important ly ▁p ear l ▁mil let , ▁s org hum ▁and ▁cow pe as , ▁which ▁spread ▁through ▁West ▁Africa ▁and ▁the ▁Sah el . ▁The ▁Sah ara ▁at ▁this ▁time ▁was ▁like ▁the ▁Sah el ▁today . ▁Its ▁wide ▁open ▁fields ▁made ▁cultiv ation ▁easy , ▁but ▁the ▁poor ▁soil ▁and ▁limited ▁rain ▁made ▁int ensive ▁far ming ▁impossible . ▁The ▁local ▁cro ps ▁were ▁also ▁not ▁ideal ▁and ▁produced ▁fewer ▁cal ories ▁than ▁those ▁of ▁other ▁regions . ▁These ▁factors ▁limited ▁sur pl uses ▁and ▁kept ▁populations ▁sparse ▁and ▁scattered . ▁ ▁North ▁Africa ▁took ▁a ▁very ▁different ▁route ▁from ▁the ▁southern ▁regions . ▁Cl imat ically ▁it ▁is ▁linked ▁to ▁the ▁Middle