The generational change in the mid-21st century was an unprecedented process. It was the first time humanity completely altered the genes of its own species. Humans transitioned from "Homo sapiens" to "Benchmark Humans" who were reproductively isolated from Homo sapiens.
This was the first time in history that there was a true appearance of "two kinds of humans." Even though in history, when groups with significant differences in appearance came into contact, there were instances where "one side would not view the other as human" or "both sides would see each other as 'non-human'." However, in most cases, those ancient people understood that they could produce offspring with other groups, and there was no "reproductive isolation." Even between Homo sapiens and Neanderthals, there were cases of mixed ancestry.
But between Benchmark Humans and Homo sapiens, there truly existed reproductive isolation.
