There are published papers on the probabilities involved in this scenario. Maybe we need a specific thread for them? With some papers archived for easy access for newcomers…
Granted, “Genealogical Science” is not exactly a text book topic… and I’m happy to use another label for what is the governing elements to multiple mated pairs becoming Universal Ancestral pairs for everyone alive in the world today.
It is a subfield of population genetics. There is an immense amount of work done to understand how pedigrees interact with genetics. Pedigrees are essentially a synonym for genealogy.
For biparental species, almost every one who leaves grandkids becomes a universal ancestor eventually.
Race as biological category is disproven with monophylogeny, and genetic evidence that we find interbreeding everywhere.
In genetics we do a lot of work untangling the effect of local ancestry. In medicine we do use race as a very imperfect proxy for disease markers and response. Talking about differences in a value neutral way is not racist.
However making claims about differences in genetic intellectual capabilities at level of race is both emperically false and becomes racist very quickly. Notice, at no point have we done this.