That would mean that slavery was the purpose of denying them the information, not the other way around. Nobody said or thought "let's enslave these people in o

That would mean that slavery was the purpose of denying them the information, not the other way around. Nobody said or thought "let's enslave these people in order to deny them information about their ancestry" or "let's enslave persons of African descent in order to keep them ignorant". The chain of purposes is "I don't want to do this shit work, nor do I want to pay anybody else to do it" therefore "I'll force somebody else to do it for free" therefore "I'll keep them as ignorant as possible to make it harder for them to resist".