Between Chimp-Pig and Superman

We humans share a lot of DNA with chimps and other primates, so there’s no real doubt we reside fairly close to these other creatures on the evolutionary tree.   But yet, there are some major gaps in the standard story of how primates transitioned into humans.   I’ve recently become aware of a novel, eerily compelling, hypothesis that – if accepted – would appear to fill these gaps quite nicely.

To put it simply, the hypothesis is that: Somewhere back in early proto-human history, there was a primate-pig hybrid.  Most probably a hybrid of a pig with a chimp, or some sort of proto-chimp.

The idea was publicized via a Physorg post a month and a half ago — but somehow I missed that post when it came out, and just noticed it recently due to a tip from a colleague.

The theory seems outrageous at first, but once you read through the detailed argumentation, it starts to seem reasonably convincing – and then disturbingly, fascinatingly believable.  Although of course, lacking slam-dunk evidence, it remains an intriguing speculation…

The creator of the hypothesis, the geneticist Eugene McCarthy, has written a wonderfully clear exposition of the available evidence.   In fact his essay is so accessibly written that I’m not going to bother giving you a point-by-point recapitulation of his data and argumentation– my main goal in this brief article is just to direct you to McCarthy’s essay, and say YOU MUST READ THIS.

McCarthy is an expert on hybrids, and marshals extensive evidence that distant species can, indeed, mate with each other and produce viable offspring.   It doesn’t happen all that often; but evolution is built on things that don’t happen often – yet provide interesting advantages when they do happen, which are then propagated through the generations.

The multiple resemblances between humans and pigs have been repeatedly noted by various artistic minds, most dramatically by George Orwell in Animal Farm.   South Park fans will be reminded of Eric Cartman’s classic song and dance routine.   Medical researchers are well aware of the peculiar compatibility between pig and human, which is why some current xenotransplantation research centers on transplanting pig organs into humans.

McCarthy gives an extensive list of human characteristics that differ from ANY primate, yet closely resemble pigs.   One interesting point is the way human backbones combine primate characteristics with pig characteristics.   In his analysis, what enabled early humans to start walking upright and come out of the trees down to the ground, was the combination of more pig-like backbones and more pig-like big butt muscles.

Obviously — our cartilaginous noses, omnivorous eating habits, pudgy hairless skin and dozens of other piggy traits notwithstanding — we’re on the whole more primate-like than pig-like.   But McCarthy’s hypothesis is not that we’re half-primate / half-pig; it’s rather that, at some point way back when, a pig mated with a primate, producing a hybrid that then mated with a primate again.  After a few more generations of back-crossing with primates, one had a strange sort of primate, blessed with various pig characteristics.

If we have partly piggish origins, why isn’t this obvious from our DNA?  Because genetics is complicated.  In general, when a hybrid of species A and species B back-crosses with species A, and this back-crossing is continued over many generations, it can be fairly hard to pick out the traces of species B in the DNA of the resultant descendants  — even when clear traits resulting from B exist in the descendants’ phenotypes.

It does seem to me that it might be possible to use machine learning technology to search for primordial pig traces in the human genome.  Suppose one started with a database of genetic information from multiple examples of organisms known to arise via hybridization followed by repeated generations of back-crossing.   Potentially, one could then train machine learning algorithms to recognize the hidden signatures of ancestral hybridization.   These signatures could then be searched for in the human genome.   It’s an interesting research direction — though it wouldn’t be easy; for sure one would need extensive proteomic data as well as genomic data.   Hybridization with backcrossing is a case where one may see approximate preservation of tertiary protein structure even as gene sequences change over time.   Still — perhaps AI technology, which will one day likely dethrone us as the smartest on the planet, will also allow us to better probe the nature of the beasts from which we originated.

From a broader evolutionary-theory perspective, a confirmation of hybrid human origin would constitute yet another piece of evidence that creative leaps often emerge from synergetic or symbiotic combination of disparate, independent entities.   The current cell emerged via symbiogenesis from early, simpler cells and mitochondria, which used to be separate entities.  DNA and RNA may have existed separately at once point, then fused together into a common machinery.   Creativity in the human mind is often explained via concept blending.  It could be that many of the punctuated equilibria observed in the evolution of species, were actually triggered by cross-species hybridization.

But I imagine most readers will be less drawn to the evolutionary-systems-theory implications, than the qualitative human aspect of the hypothesis.

I find that, since reading McCarthy’s essay, I look at people a bit differently.   Put simply: Everyone looks a good bit more piggy than they used to.  It’s a disturbing, yet somehow oddly satisfying feeling .  Looking at the world through the eyes of the primate-pig origin theory, I feel almost as if the piggish nature of human beings was really obvious to me all along, at the gut level, but just not something I explicitly acknowledged … due to the lack of scientific back-up, which Dr. McCarthy has now graciously provided.

Try it for yourself.   Read McCarthy’s list of human-pig parallels — then do some people-watching, perhaps in a crowded buffet or bar, or the nosebleed seats in the stadium at a sporting event.   Peruse various photos online, of your fellow homo sapiens, particularly when engaged in acts of consumption or states of strong emotion.   Yes, there’s a lot of monkey there – no one rational could doubt that — but don’t you see a fair bit of pig as well?

Nietzsche observed that “man is a rope between animal and superman.”  As a good transhumanist, I tend to agree.   But as a friend quipped when I pointed McCarthy’s theory out to them, perhaps a revision is in order….

“Man is a rope between chimp-pig and superman” ?

Maybe….

28 Comments

  1. Additional comment to Tony:
    Virtually all of Myers’ objections are, I think, satisfactorily addressed in the second Physorg article or in the my comments at the bottom of that page.

  2. Response to Ethaniel: I first wrote up the pig-ape hypothesis of human origins in about 1988. I also gave a couple of seminars on it in the genetics department of the University of Georgia in 1995.
    Response to Tony: The “refutation” you refer to is merely P.Z. Myers employing his usual intellectually invalid modus operandi: setting up straw men, quoting out of context, and preaching to the choir. Good for box office. Bad for truth.

  3. I’ll just leave this link here in case someone wants to read a refutation of this hypothesis by a developmental biologist: http://scienceblogs.com/pharyngula/2013/07/02/the-mfap-hypothesis-for-the-origins-of-homo-sapiens/

  4. Was McCarthy inspired by a 1998 novel?

  5. When you look back at Darwin’s writing, he got it right – he claimed that ‘natural variation’ present within the animal, was gradually sculpted by environmental pressures into a creature of optimal survivability – he acknowledged that he did not know where this ‘natural variation’ came from.

    The problem for Darwinian Theory came when we discovered Genes and DNA and some bright spark decided that it was natural random micro mutation of the genes that was the source of Darwin’s ‘natural variation’, despite the fact that such a process could never explain the reality of the fossil record – that species came into existence almost instantaneously and then remained static until extinction…

    Now, thanks to McCarthy, we do know where this natural variation comes from – it is the genetic storm of mutation caused when the F1 hybrid attempts to make gametes from the mismatched genes in its chromosomes. The molecular machinery which carries out this process (the Holliday junction) is now well researched, even down to the process where the junction randomly swaps nucleotides, creating a veritable storm of mutation. This also accounts for the appalling infertility of most F1 hybrids, because their gametes are so mutated, the majority are simply non viable.

    However, the F1’s themselves are perfectly viable, and given time, eventually a gamete is produced which is viable and so the back crossing into one of the parent lines begins the process of improving the all important fertility. McCarthy calls this all important process of fertility building ‘Stabilisation’, and it is happening in parallel with the other well established aspects of natural selection of refining the new proto-species to fit into the various ‘arms races’ around it.

    Two important predictions and realisations jump immediately from the McCarthy model of hybrid induced variation.

    The first is that genetic richness is highest at the formation of the proto species, but is progressively whittled away by natural selection, leaving the identifiable species with ever decreasing pool of natural variation. This ‘sterile genome’ is eventually at the mercy of environmental change and so extinction is guaranteed. The McCarthy Theory predicts that extinction awaits all species that fail to hybridise regularly and keep their genome in a rich state of diversity.

    The second is that characteristics which do not influence fertility will be progressively lost as Stabilisation progresses… While intelligence is clearly an important survival trait, it either has no impact on fertility, or in humans can even have a negative fertility impact as intelligent couples choose not to breed while Idiocracy has no such constraint. The consequence of this is that fertility is optimised at the expense of intelligence – our founding F1 parents were inevitably much more intelligent than we are and our species will continue to loose intelligence in favour of fertility.

    Perhaps if McCarthy’s work could be encapsulated in 140 characters, it might be more accessible to a large part of today’s humanity.

  6. Surely you would just look at the sequence data of humans and chimps, see which genes are different and then build primers for the human versions and then look for them in pigs. No? I mean I know “Genetics is complicated” but we’re pretty bloody good at it nowadays.

    I mean obviously we already effectively did this when we built genetic phylogenies of the species, but I mean if you want to pretend that doesn’t work because magic, then the above is a pretty simple method. Maybe £5 per loci for primers and sequencing if you do them in batches of 96, not really that much in the scale of things.
    I mean it would take much less time than it took that guy to write his book. Maybe a month?

    • (Yes, I’m the same Gene McCarthy that’s proposing the pig-chimp hybrid theory.) I thought it would be a good idea to explain the problems with Adrian’s comment. First of all, it’s not so easy get a list of sequences that differ in humans and chimps. You would have to either carry out a comparison of the human and chimp genomes yourself, which would be incredibly complicated and time consuming, or you would have to get a list of such differences from those who have carried out such a comparison. But the researchers who have such information have not shared, and are unlikely to share, the specific information they have gathered. From their point of view, they are the ones who have gathered the information and they think of it as proprietary. They think they will be able to use it to produc e publications and enhance their reputations. Scientific research is extremely competitive and labs that have information often do not want to give other labs a leg up by sharing that information. So that’s one problem. But the biggest problem, in my opinion, is that if humans are pig-chimp hybrids of the type I’m suggesting, you don’t expect there to be many sequence differences between a human and a chimpanzee . Only a few generations of backcrossing to chimpanzee would rapidly eliminate the vast majority of initial sequence differences (this is explained in detail in the green sidebar on this page of my website). So under the hypothesis that I’m proposing, you wouldn’t really expect humans to be very different from chimpanzees in terms of nucleotide sequence comparisons. And, in fact, as most people know, they differ very little in this respect (comparisons of this type indicate that we are about 98-99% similar to chimpanzees). So what are these human sequence differences, Adrian, that we are supposed to compare with pig? At this point in the discussion, many people ask “Well, why do we differ from chimpanzees with respect to so many traits then?” The explanation that I offer is given here.

  7. My reaction to encountering this theory was the same as yours; I started to see piggishness everywhere. What once was hidden was now clear.

  8. Sorry, no ‘s’ on ‘Pierian Spring’.

  9. It may help in trying to appreciate this bold and apparently shocking proposal to turn the question around to this: How else did we become human.

    The best evidence we have for the radical divergence of our ancestors from the rest of the primates is a different hyoid bone. The difference is mainly in the position rather than the shape.

    The question is not just how did it become different, but how did it become different in a way that enabled sufficient numbers to survive and take advantage of this change.

    This is a simplified but an unavoidable question. I have been following and thinking about Gene McCarthy’s theory for a little while now and there is no question it deserves a fair hearing, and testing. The abusive people who have done some basic biology would do well to heed Alexander Pope’s great lines:

    ‘A little learning is a dangerous thing/ drink deep or taste not the Pierian Springs/There shallow draughts intoxicate the mind/And drinking largely sobers us again”

  10. With regard to Armand’ comment: “This is on the same level as the Ancient Astronaut hypothesis.”

    The Ancient Astronaut hypothesis has become popular due to an acceptance that mankind has evolved from cave-dweller to today’s level of technological sophistication. Thus any evidence of earlier technology HAD to arrive from off planet. The pig/chimp hybridisation hypothesis provides a challenge to established scientific “doctrine” and could revolutionize our thinking on what we consider to be out-of-place-artifacts.

  11. I don’t think this theory has any rational or scientific arguments going for it. It is based purely on the observation that Humans share some superficial similarities with domestic pigs. There is no fossil or genetic evidence to support it. It would be like saying that Dolphins are shark hybrids because they share some superficial traits. In both cases, convergent evolution is a much more plausible explanation than hybridization. I would also like to point out that pigs only exist due to Humans selectively breeding boars. Millions of years ago there were no pigs. Proposing that Humanity exists because an Australopithecus created a fertile offspring with a wart-hog is an extraordinary claim, and extraordinary claims require extraordinary proof.

    • Armand, your equation of “scientific” with “fossil or genetic” doesn’t make sense to me. Also, the shark/dolphin analogy fails — detailed comparison of internal organs of sharks and dolphins doesn’t show similarities, and I really doubt sharks would show any special promise in terms of xenotransplantation of their organs into dolphins….. Your counter-advocacy is not engaging with the actual arguments or evidence presented by McCarthy… — Ben G

    • As for “extraordinary claims require extraordinary proof” — if you think about this maxim in terms of Bayes Rule, what it means is that if one has a stronger prior bias against a certain statement, it takes more evidence to overcome this bias. The question then becomes, in this case, why one should have a strong prior bias against the chimp-pig theory and in favor of the primates-only origin theory. I guess Occam’s Razor could be interpreted to assign a higher bias to a one-species origin story, but this is a fairly weak argument (a 500-species origin story might sensibly be downweighted for sheer overcomplication/overfitting, but 2 species is not THAT many…)….

    • but dolphins (mammalia) DID evolve from the same sort of pre-historic lifeforms from which sharks evolved! Even we share similar body organs and tissues .. Cartilage? for sharks their supporting structure IS cartilage ! Liver? intestinal tracts? the list is long ..
      I fear you are not seeing the trees because of the forest …

  12. I agree entirely with the author of this article. Dr. McCarthy has done a magnificent job of presenting the evidence, which builds a most compelling argument worthy of testing.

    What is particularly noteworthy are the many traits we have that no other primates have, like the vertical rather than lateral vascular development of our skin, which we as primates share uniquely with pigs.

    Dr. McCarthy has had the courage to examine what might be considered an outrageous question with the utmost scientific rigor. When has that ever happened before and led to a sea-change in our understanding of our origins?

  13. How would you place this hypothesis on a continuum of plausibility with the Aquatic Ape hypothesis? Some of the physical consequences of hybridization with pigs seem empirically equivalent with physical consequences of aquatic habitat — backbone changes, hair loss, layers of fat, even changes in the nose.

    • Cameron — The physiological similarities with pigs seem significantly greater than with aquatic mammals. So IF McCarthy is right about the general plausibility of cross-species hybrids, then I’d say the chimp-pig theory is significantly more plausible….

      Apart from detailed proteomic comparison of pigs and humans, then, the main thing that can be done to move toward validation/falsification of the chimp-pig hypothesis is exploration of hybridization — between current primates and pigs, and also between various mammal pairs. I guess a lot of this could be done in the test tube. This kind of work is not that hard or expensive, but according to my understanding, also is ot well funded at present.

      • I think it could be added that many of the sorts of pig-like creatures common to the Bonobo ranges are able swimmers and quite fond of water, so I don’t think it is automatically necessary to think of the pig-ape conjecture as incompatible with the aquatic ape conjecture; perhaps the pig-ape was just more comfortable with water, having subcutaneous fat, less body hair and a more streamlined posture etc

  14. The support seems to be given ad nauseum but isn’t this theory still destined for a back burner? It’s a pretty bold challenge to the central dogma and the hard physical evidence has essentially turned to stone. Is this another one that will sport a “not falsifiable” tag and sit on the “not hard science” shelf?

    • Tory — I suspect that once the various omics have developed further, the chimp-pig hypothesis will be falsifiable via analyzing proteome+genome etc. — Ben G

    • This is absolutely not a challenge to the central dogma of molecular biology, and doesn’t imply something genuinely silly like protein-to-DNA reverse transcription.

      What it does challenge are some well-loved hypotheses, but hypotheses are ablative anyway.

      This should be easily falsified with computational methods and simple pattern matching – just looking for sequence data shouldn’t be hard, and looking matches in the primary amino acid sequence is only slightly harder than looking for matches in the DNA sequence. Secondary and tertiary structure are still a hard problem, but sequence data should be a good first place to look for falsification or confirmation.

      • I would caution that there are many many ways to bend a pretzel arriving at the same physical final shape.

        Hence, in my opinion, genetic analysis would seem to be highly unlikely to answer important questions in this matter.

  15. Four legs good, two legs better, indeterminate swarm of cyber-tentacles best!

  16. Are you seriously endorsing a wildly speculative theory with no actual evidence to support it? This is on the same level as the Ancient Astronaut hypothesis.
    “I don’t know, therefore chimp-pigs.”

    Macroevolution is a creationist term, and any website that would call itself that is unlikely to adhere to the scientific method. This article belongs on the Onion as an explanation for the obesity epidemic.

    • Armand — I’d be more curious to hear your opinion after you read the information on the macroevolution site…. And no, that site has nothing to do with creationism.

      I don’t endorse the hybrid origin theory in the sense of considering it almost-definitely true (in the sense I consider the origin of humans from animals by evolution almost-definitely-true)…. But it seems rather plausible to me….

      I’d be happy to hear rational, scientific arguments against the theory; but you certainly haven’t offered one…

      — Ben G

    • Your criticisms are noted, and noted to be more speculation, misinformation, and baseless conclusions. “No evidence”?? Countless advances in scientific understanding were realized only because an investigator ‘had a hunch’ and followed thru. I would say that our ‘possible porcine progenitors’ possession of 100% of the 107 or so features listed by Dr. McCarthy that distinguish us from other primates represents much more ‘evidence’ than necessary for further work.
      Your description of ‘macroevolution’ as ‘Creationist’ is nothing short of absurd: Evolution is *known* by scientists to be a consequence often of much more than mere DNA mutation. Dr. McCarthy’s book on the topic of ‘hybridization among birds’ is a significant contribution to hybridization’s influence on species differentiation/evolution.

      Might be a good idea were you to actually read thru his elequently, logical, and scientificly informational discussion…

      tkjtkj, m.d.

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