I have read a lot about how North Africans are ethnically Caucasoid Berbers and culturally Arabic. Ancient Egypt was a spiritual and cultural hub historically. They have many technological achievements to their name. So how and why did a cultural power like North Africa absorb Arabic culture and religion?
EDIT: Removed a large chunk of my answer. Thanks, shlin28, for correcting my knowlege on the status of Roman N. Africa prior to the Muslim expansion.
Around 1100, a tribal confederation known as the Bani Hilal- numbering some 200,000 men, women and children in all- moved from the Arabian Peninsula to Egyptian and fought the ruling Fatimid dynasty. They would eventually be defeated by both the Fatimids and the Almohads, but they ended up setting in the N. African hinterlands, spreading Arabic much further than the urban population centers in which it was previously situated.
North Africans are ethnically Caucasoid Berbers
What's the source for this? North Africans aren't a monolithic group and race isn't a scientific grouping.