July 10, 2013
to be posted on nobabies.net
Eugene M. McCarthy
Dear Dr. McCarthy:
Let’s see whether I can be helpful.
I have read your web site http://www.macroevolution.net/human-origins.html with great interest. I was lured thither by a note posted on one of my favorite sites http://hbdchick.wordpress.com/ and I plan to post this one on my own http://nobabies.net. The traffic I attract will probably not result in an avalanche coming your way, but I do what I can. I shall not give away your thesis as you present it more dramatically than I could.
I do like your argument. I shall indeed keep an open mind on the issue. And I by no means find it repugnant; what people are doing right now is plenty to shudder about.
The first thing that strikes me is that the “party line” of something dividing into gorillas on the one hand and something chimpanzee-like on the other hand and then the chimpanzee line branching into human and chimpanzee, both regular and pigmy, has always bothered me. There was a cartoon “Terry and the Pirates” many years ago. In one episode Terry, in a city deep in the Far East, runs into an opium den looking place and demands of the man in charge, “Did a six foot American with a full red beard just come through here?” In those days few were that tall and essentially no American had a beard, least of all a red one. The Asian responded serenely, “Who can say? All Americans look alike.” The joke was that Americans used to say all Chinese look alike. We all suspected that it was just our own prejudice. Anyway, with the old man I must say, “All gorillas and chimpanzees look alike.”
The size different strikes me as well within the human range. Ditto social differences. We outswim, outrun and outlast them in the desert. These are skills they would find useful. We scale cliffs, endure cold, explore caves, bring down animals bigger than ourselves (yes, a man can wrestle a bull to the ground). And that is not even mentioning our more versatile voices and bigger brains and tool use. In other words the party line requires that we evolved a lot faster than they did. A hybridization event does have a lot of appeal.
The second thing is that I once had a friend I have alas lost touch with who told me somebody in his family had managed to breed a mule and to continue breeding for five generations, whereupon he stopped because there didn’t seem to be any point in going farther. I wish I could refer you to my friend. Despite the obvious importance of the message I did not ask whether all the generations were back crosses in the same direction nor whether he even arrived at a fertile male descendant.
The third thing that comes to me is the red wolf. According to what I have read there are three types of wolf: the grey wolf, the timber wolf and the red wolf. There are genes the grey wolf has that the timber wolf lacks and vice versa. On the other hand the red wolf has genes that it shares with the others and there are no genes that the red wolf monopolizes. The implication is that the red wolf is a hybrid. On the other hand the article says, “grey wolves and timber wolves do not hybridize.” So the argument was to consider the red wolf to be a bona fide species. It seems to me that the same technique should be able to tell whether some other species than just the chimpanzee is ancestral to us.
The fourth is that personally I might have gone with the manatee. The dolphin has a sphincter with which it can shut its airway from the sea but no other defense. A person can hold the nose, often can shut the nostrils with the upper lip, can close the lips, can filter air or water through the teeth, can descend to depths below where most large bodied life is found, can close the mouth with the tongue in any number of ways, can pump air or water in or out with the tongue and cheeks, has a soft palate, true vocal cords and maybe functional false cords; I never thought to check with a fluoroscope. The Australopithecus had bigger feet than we do – built in swim fins. I keep an open mind on whether we were aquatic, and I really like manatee. It never occurred to me before to wonder whether they could be ancestral.
Fifth, and this should probably have come first, is at last there is somebody who thinks as far outside the box as I do.
The sixth and final point is tricky. Your interest is in the possibility of hybrids between very distantly related form, even soto voce different orders. That is most daring. My interest is the loss of fertility entailed by couples related so that they are separated by fewer than ten generations. On the face of it we should be natural enemies, but not so. You point out that among hybrids one sex is more affected than the other; in mammals the female is more likely to be fertile than the male. The line can survive if the hybrid female is back crossed with a male that is not hybrid and you propose that this can be pursued generation after generation until hybrid males emerge. My observations suggest that when rather unrelated – ten degrees of separation – mammals mate that serious infertility results after this pattern is pursued generation after generation with the male being harder hit. It appears that we may be at opposite ends of the same elephant.
The effect I see develops so quickly and so predictably that it cannot be a matter of DNA mutations. The mechanism has to be epigenetic. I attach a paper I was involved with that takes a first step in working out the mechanism.
Your theory is quite in keeping with Charles Darwin. I read Origin of Species in hopes of finding something out about what people think about the origin of species. I was disappointed to find he had just one word to offer, “happenstance.” In other words he had no idea about why speciation develops and I can’t see that we have advanced a lot. So far as evolution by selection, you point out that the ancient Greeks discussed whether people got smart by using tools or started making tools because they were smart. That seems to sum up evolution by selection as well as Darwin. Where Darwin parts company with them is that – it is commonly said – the Greeks expected ideal forms. For Darwin species don’t exist as they blend imperceptibly with each other.
I think the superficial difference between us can be resolved by one possible observation. It is not immediately obvious why a back cross should work. But during back cross I would expect that your strategy will work – wait for it – if the male is a closely related male.
If so, then it is a no brainer. The epigenetic mechanism evolved until it could produce high grade infertility and then, of course, it progressed no farther. There would be no evolutionary pressure to do so. The reason why there is such pressure is contained in my own web site. Check out
http://nobabies.net/A%20December%20summary.html
toward the end. So the epigenetic mechanism pushes just barely hard enough to do the job. This is in gross contrast with Darwinian “happenstance,” whereby the genes (yes I know Darwin never read Mendel, but he knew perfectly well something was being inherited) just morph over time from selection and random drift until they can’t do business with each other. By that logic the possibility of hybrids outside of the same genus is patently absurd; and I’m sure you have run into that reaction.
I take as an axiom, although based on the best data I can find, that speciation on a genetic basis occurs at about generation two thousand. But that does not mean hard and fast mutual infertility. Such infertility is robustly augmented at least by the pre-zygotic component of the epigenetic mechanism. But this part of the mechanism can be overridden. It just barely works anyway and sooner or later a lucky combination of epigenetic markers just might work.
So I am making a prediction about data you may have and I certainly don’t have; I say that back crossing is done with closely related males.
There. I have run on quite a distance. There is the possibility that we should not make common cause here for strategic reasons. Each of us can freak people out already. Maybe they don’t need a double dose. But I have certainly found that your idea, quite novel to me, put me to thinking. So many thanks for that.
Let me know what you think.
Sincerely,
M. Linton Herbert MD
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