Major West African empires formed around what?

The history of West Africa has been commonly divided into its prehistory, the Iron Age in Africa, the major polities flourishing, the colonial period, and finally the post-independence era, in which the current nations were formed. West Africa is west of an imagined north-south axis lying close to 10° east ... The Ghana Empire may have been established as early as the 7th century ...

Explanation:

each morning i wrote my name

on the dusty cabinet, then crossed

the dining table in script, scrawled

in capitals on the backs of chairs,

practicing signatures like scales

while mother followed squirting

linseed from a burping can