Sigh. Yes, I don’t get it. I’m not sure why @dsterncardinale thinks I don’t want to get it when I’m specifically asking. I understand there could be back mutations. I understand how alleles could be lost in autosomal DNA. I understand how mutations could be lost if there’s less than 1 mutation per generation in mtDNA or the y chromosome. I don’t understand how they can be lost if there’s multiple mutations per generation in uniparentally inherited DNA. If every male passes on 3 mutations approximately, someone is going to have a male child if the population is growing, so I don’t understand how the mutation rate and substitution rate would be different over time.
I DO want to understand it. I think population genetics is interesting but I know it’s not intuitive, so I do know the likeliest outcome is that I’m drawing a blank because I’m not understanding correctly and I would like to get it. Hopefully my explanation is helpful to see where my misunderstanding lies.