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I cannot believe a person with those academic credentials could ask such a stupid question. The genetic variation and natural selection argument seemingly cuts that to ribbons.

That ought to cut both ways, though. One of the Great Mysteries, it seems to me, is why mitochondria have never developed an adaptation that attacks or interferes with arriving sperm that carry a Y chromosome.

If I'm a mitochondrium, and I'm in the egg waiting for a sperm to come along, it is in my interest to kill any Y-bearing spermatozoa. The only way my genes get any farther than one more generation of humans is if this egg I'm in gets fertilized with an 'X'.

If this adaptation had ever arisen, it would be noticable in maybe 50 or 100 generations. We would see 60-40 or even 70-30 ratios of female to male babies being born. This would be a highly successful adaptation for the mitochrondria. Can you think of any reason why this could not happen?

Maybe sperm themselves have adapted to whatever adaptations mitochondria may have made, or maybe distinguishing between X and Y bearing sperm is beyond the capability of a mitochondria. Or maybe it is not in their interest, as the elimination of all Y bearing sperm would kill off the species by making reproduction impossible.