That reminds me of Charles W. Chesnutt.
What reminds me of the great author is not that individuals displaying the full range of human variation will always be born, due to DNA's digital encoding, even if intermarriage becomes the norm. That point has been beaten into the ground in these parts.
I am reminded of Chesnutt because of the question of "racism" in a society with an endogamous color line versus "colorism" in societies without one. Obviously, people cannot oppress their own children, siblings, or parents on the basis of their victim's ancestry. Equally obviously, they can mistreat them because of their looks. Many books have argued that one form of injustice (mistreatment for one's ancestry, versus mistreatment for one's looks) is worse than the other. The former leads to state-enforced terrorism but spawns solidarity and resistance. The latter leads to acquiescence (and the advice to marry light) but your lighter-skinned relatives will always take you in.
Chesnutt believed that the latter prospect was America's destiny. In his 1900 essay "The Future American" he saw that intermarriage was legal almost everywhere and, in certain regions, even common. With great hope in the future he foresaw that as Americans intermarried an increasing fraction of the population would have African as well as European ancestry. He affirmed that he lived in the best of times because America was on the verge of abandoning racism (ancestry-based mistreatment). He glossed over the likely perpetuation of colorism (appearance-based mistreatment) or perhaps he thought it less wicked. In any event, he joyfully believed that in 1900 he had the good fortune to be alive and writing at the dawning of a new age, when Americans would embrace all their ancestries.
It is the saddest essay I have ever read.
As you all know, Chesnutt was dead wrong. Over the next ten years intermarriage was outlawed throughout the nation. The one-drop rule was made law in the decade after that. The nationwide lynchings rose to one per week for months on end. Chesnutt became increasingly disillusioned. Eventually even the President of the United States proudly wore a klansman's robe.
Chesnutt lived until 1932. By then he had abandoned his writing career because his market had dried up. His work had become too bitter for the public to swallow. The following short story is an example of his later work. It is so true that it will make your skin crawl. Read
The Doll (1916).