Giant cities, complex law codes, extensive trade expeditions, steelworking, and standing armies.
Certainly there were still many very primitive parts of Africa, but in rhe fifteenth Century the only real advantage the Europeans had was better art, and then only if you're going to give all Europe credit for the Italians.
I don't know why it hurts you feelings so much to find out all Africa wasn't significantly less technologically advanced than Europe at some point in History. Like I said, Europe pulled far ahead in the intervening centuries, although most of the parts of Africa which had been at about parity to Europe were the last to be colonized.
Sixteenth Century Portugal had a military advantage in cannon which helped them to take over most of the cities of the Swahili coast, although they would themselves be ousted by the Omani until the British and Germans showed up in the late 19th Century.
To the other guy, the technology of the wheel is good for more than just carts, not that carts are indeed worthless in Peru. Wheelbarrows, potter's wheels, and water / windmills are all extremely useful inventions that require the wheel. Lacking that technology was a severe handicap.
Mind you, I'm not saying they were inferior people because they didn't have these things. I'm saying they were technologically backwards.
I don't think human sacrifice necessarily has anything to do with technological advancement, but then again, all the other instances of human sacrifice you mentioned were thousands of years in the past by Century XV. And mentioning thr Romans is quite disingenuous. They killed less than ten foreigners to appease their gods when it looked like Hannibal was about to take and destroy the city. This is hardly the same as the Aztec confederation capturing thousands of people and cutting their hearts out on top a pyramid as a matter of course. But I digress.