While gardening in my yard, I occasionally come across arrowheads and other pieces of worked stone. One of my flowerbeds contains a large pile of chipped and broken bits as if the spot had once been a trash dump of sorts. That could just be my imagination, but I left the area intact, planting around it. Perhaps I shall explore the bits and pieces again someday.
My home is in a lakeside community near Tallahassee, Florida, and that flowerbed shows me that other peoples once lived in the lake area not so very long ago, historically speaking. Their world has been replaced by my world, one that they wouldn't recognize.
There is still abundant wildlife around the lake, hunted enthusiastically by my neighbors when hunting season comes around. But the original Native American hunters who took from all this bounty of water and game are completely gone. Or are they?
My husband has some Seminole ancestry. From a picture of his grandmother and his sequenced genome, we know this is so. My genome also reveals a smidgen of Native American ancestry, and I've known many people here in the southern United States, both White Americans and African Americans, who say they are part "Indian".
When archaeological history is closely observed going back millions of years, the record shows that hominin groups were constantly replacing one another. Often a period of overlapping history would take place, and then one population seemingly disappeared forever. The survivors of that encounter would eventually be replaced themselves by yet another intruder. Dated soil layers containing bones and cultural artifacts tell us the ancient story of "who replaced whom".
The cultural objects and even the skeletons of two groups are often quite different, so it's understandable to believe that a total replacement took place when looking at the archaeological record. But less than ten years after the hunan genome was sequenced, we found out that many of us carry Neanderthal ancestry, and now we know that many Modern Humans today have Denisovan ancestry as well. There are also hints of very ancient lineage in some genomes--perhaps Homo erectus.
It seems to be a given that when one hominin group migrates into another group's territory, the leading edge of the invading group will mate with the overrun one to a greater or lesser degree. This happens regardless of whether the intruders are aggressors or simply tolerated by the present inhabitants. This commingling often continues after the invading group becomes settled, if fairly recent history is any indication. (Mexico is an example.)
But it's important not to be overly academic when writing fiction--or when thinking about past and present events. Just as the world's peoples do today, every historical group has had to live within its immediate present. If a culture rich in personal freedoms and relative wealth is overrun by a repressive intruder that enslaves some of its members and kills most of the rest, it would be difficult to explain to the survivors that all is not lost. Knowing that their culture and genomes wouldn't completely vanish from the earth would be of little comfort. A lot of real suffering happens during historical shifting. Excesses of behavior are unleashed during those times that can only be described as evil. I find replacement an interesting subject to write about from a historical standpoint, but "The Chronicles" wouldn't be complete without including the age-old themes of good and bad.