I'm brainstorming an alternate history where the entire human species (Homo sapiens) somehow stays within Africa instead of dispersing elsewhere. Europe and the Middle East would thus remain the domain of the Neanderthals whereas Denisovans occupy Asia, Australasia, and possibly the Americas.
Since all Homo sapiens remains in Africa in this scenario, it is there that most of the world's major civilizations develop. Many of these resemble the African civilizations of our world, such as ancient Egypt, Kush, Ethiopia, Mali, and Great Zimbabwe. However, one notable difference is the absence of Eurasian and American crops and livestock in their agricultural systems. Instead, all the crops that humans grow are native to Africa (e.g. sorghum, pearl millet, and yams), and they have also domesticated African animals such as the donkey, wildcat, spotted hyena, buffalo, and zebra. In addition, metalworking in this alternate timeline is a West African innovation before spreading to the Nile Valley and sub-Saharan lands.
Meanwhile, most of the Neanderthal and Denisovan populations continue their traditional way of life, namely that of small and territorial bands of hunter-gatherers. A distinctive exception to this rule appears in the Middle East and the Mediterranean coast of Europe, where the local Neanderthal populations have learned the methods of agriculture and metalworking from the Egyptian civilization. These "civilized" Neanderthals have even coalesced into primitive city-states comparable to the early Greeks and Mesopotamians.
The question I wish to start off with is what international trade would look like in this kind of scenario. In our own timeline, quite a number of African civilizations (e.g. the ones in West Africa, Ethiopia, and the Swahili coast) benefited from trade with Eurasian cultures. However, in my scenario, most of Eurasia and the rest of the world belongs to territorial, culturally conservative, and xenophobic hunter-gatherers. Pretty much all of Africa's external trade contacts would be the Middle Eastern and Mediterranean Neanderthals I described in the previous paragraph, and even they are broken up into squabbling city-states. Or could African humans somehow expand their trade connections beyond this region?
EDIT: On second thought, even the most xenophobic Neanderthals might be willing to trade if they got something desirable from it. So never mind the question I asked at the end. I am still proud enough of the original concept to share it though.