Geneticists/people of metal at the University of Nairobi conduct a centuries-long genetic engineering initiative that transforms biological Africans into an entirely new, immeasurably smarter human species. Meanwhile, the people of metal who led the Human Rescue Initiative in Africa have built human colonies on two distant planets to assure that humans survive somewhere.
Colonists find strange mosaic-like formations of small stones at ground level on both planets. They form identical patterns that change in a fixed sequence. It's a coded message that promises God's overwhelming love to the message's recipients if they can formally prove an "unsolvable" 20th-century math conjecture and send the proof in the direction of "God's abode."
African leaders treat the message as genuine, just in case. God's love is nothing to sneeze at, if He exists. Contemporary mathematicians aren't yet smart enough to solve the conjecture, but it's only a matter of time, and genetics.