Back then, chromosomes 12 and 13 fused together to create what we now call human chromosome 2. The fused chromosome then slowly spread through the community. And then, for some reason, the group of humans with 46 chromosomes eventually supplanted the group with 48.
From your citation.
What assumptions would have to be made for this to be feasible using a population genetics model?
Without this the author is begging the question. As he is ignoring the possibility that humans and chimps are separate kinds and humans always had 46 chromosomes.
The challenge to making a feasible model is the deleterious nature of chromosome change and the relatively low frequency of this type of mutation.
In the case of Rino’s and horses they are separated by 18 chromosomes. Rino 82 and horse 64.