What makes historians think that Indo-European and I think Niger-Congo were spread via migration, but not the Afroasiatic languages?

by meme_teen

Not sure if this is right, even. Could someone help me?

Searocksandtrees

Hiya OP, please consider x-posting this question to our sister sub /r/AskAnthropology: while there are some historical linguists and anthropologists here, prehistory and human migrations are more their wheelhouse. Cheers.