At this point the argument isn't that people stayed in Africa, but that everyone outside of Africa died. At this point the 3 oldest fossils we have that look like homo sapiens are all from Morocco or the Levant or Greece, suggesting homo sapiens first evolved near the Mediterranean. But at some time between 50k and 20k years ago, all humans outside of Africa seemed to have died: Neanderthals, Denisovans, and Sapiens, all of them.
Regarding the older finds of Sapiens, when we find DNA traces and compare them to modern DNA, we are not able to find any modern population that is descended from any of this Sapien DNA, outside of Africa, that is older than even 25k.
It is well known that Sapiens arrived in Spain 40k years ago and that they demonstrated modern behavior: arts, music, advanced hunting tools, but DNA analysis suggests this group disappeared entirely, no trace of their DNA is found in existing European populations. The picture then is that 75k ago Eurasia was covered with humans, of at least 3 or 4 different species, and all of them died, and then Eurasia was repopulated by a burst of homo sapiens that radiated out from Africa.
Of course, this picture would change if we ever found some old DNA, outside of Africa, that could also be matched to DNA in a surviving group of humans.
Regarding the older finds of Sapiens, when we find DNA traces and compare them to modern DNA, we are not able to find any modern population that is descended from any of this Sapien DNA, outside of Africa, that is older than even 25k.
It is well known that Sapiens arrived in Spain 40k years ago and that they demonstrated modern behavior: arts, music, advanced hunting tools, but DNA analysis suggests this group disappeared entirely, no trace of their DNA is found in existing European populations. The picture then is that 75k ago Eurasia was covered with humans, of at least 3 or 4 different species, and all of them died, and then Eurasia was repopulated by a burst of homo sapiens that radiated out from Africa.
Of course, this picture would change if we ever found some old DNA, outside of Africa, that could also be matched to DNA in a surviving group of humans.