So colour me skeptical. As they say, extraordinary claims require extraordinary evidence, and this theory is making several extraordinary claims:
1) A hybridization event indeed occurred in the relatively recent genetic history of homo sapiens (rather than the unusual anatomic features being produced some other way).
2) The hybridization was with a close relative of pigs (rather than another family that has some similar characteristics, or multiple hybridizations that together gave us the unusual characteristics).
3) The hybridization marks the point at which hominids split from the other primates (rather than occurring later in one branch of the hominid family tree).
4) That the genes introduced by hybridization gives hominids their unique characteristics (rather than being inconsequential).
In return, the theory presents evidence (anatomic oddities and low fertility) that I would characterize as "interesting" and perhaps "worthy of further study", but certainly not extraordinary. For this to be plausible, there needs to be a second avenue of evidence, one not based on anatomic similarities...
That second avenue could be genetic, but they specifically dismiss it, presupposing a mechanism, backcrossing, that leaves little genetic evidence that it occurred. Now, I'm no geneticist, but that sounds a bit fishy to me.
If you ask a cannibal what's the taste of human flesh, he will say "pork", which makes this hypothesis funny.
That said, this is way, way too far fetched. Proposing that a primate and a primitive ungulate can produce an hybrid is already a big stretch, let alone producing a fertile one. Then, he supports his claim by refusing the genetics, and hand picks morphology aspects from the suinae that confirm his theory.
What did it for me was the "naked skin" evidence though. It's the human-selected, domestic pig that is hairless.
A primate/primitive ungulate don't need to produce a hybrid or fertile offspring since obviously aliens mixed chimpanzee and pig DNA to create us, a race of slaves to mine gold for them.
They also removed our ability to synthesize vitamin C in the process as a method of control.
His argument is that the domestic pig and the wild boar are not the same animal, which is pretty obvious. Then, he claims we don't know where the domestic pig came from, and that a common ancestor could be hairless.
That is still a pretty weak argument considering from all suinae, the domestic pig is the only hairless, and for his hypothesis to work, hairlessness would have to be a dominant trait (otherwise, logic says we should be hairy like a chimp).
I'm no geneticist or anything like that, but there are some pretty (big) holes that he doesn't address and attributes to ignorance. You can't make an hypothesis plausible by claiming about what you do NOT known - you have to show positive correlation, not absence of negative correlation.
>All useful hypothesis are, by definition, extra-ordinary.
Not in the sense of that applies to that saying. In this context "extraordinary claim" means "claim with a very low prior probability". The saying can be expressed more precisely as "in order to upgrade to the level of expectation a hypothesis with a very low prior probability, it is necessary to make an observation of very low probability generally, but high probability given that the hypothesis is true." In other words, it's essentially just Bayes' theorem.
And by no means are very-low-prior hypotheses inherently more useful. Certainly they have more impact than higher-prior hypotheses if they are validated, but in general, a very low prior means that a hypothesis is not worth wasting time considering.
In some cases, a hypothesis can be so extraordinary that it becomes practically impossible to verify by experiment. In this case, for example, the hypothesis is so unlikely that it is quite difficult to imagine an experiment (or set of experiments) whose outcome was so unlikely that it would actually make us expect that humans were descended from ape-pigs.
Yeah - but there is a real distinction between theory and hypothesis, which that guy is probably acutely aware of. (Cmd-F on one page of his site shows the word hypothesis used 17 times).
Reading a bit more, it seems like he's got expertise in a corner of science that could be relevant to what the article calls 'morphological change':
"As the increasing apparent, magnificant, speed with which morphological change can occur continues to present itself for us to comprehend, the standard theory of random mutation followed by slow environmental selection, seems to stall. In my own opinion, female choice ... , but other mechanisms of mutation ... , now need to be considered anew. The role of hybridization in driving morphological change, as McCarthy has observed time and time again, particularly in his studies of avian species ... , may be the most powerful mechanism of all."
Okay, so if the "speed of change" problem is a pretty wide-open question without a lot of firm answers, and if this guy has staked out a claim in the problem space ... my reaction is basically "good on ya'!"
Go play god with interspecies breeding and come back in 5 years with an update. :)
Minor nitpick, but while Sagan popularized the saying, it probably originates with Laplace's "The weight of evidence for an extraordinary claim must be proportioned to its strangeness" (which is itself a rephrasing).
This makes sense in historical context; the quote comes from 1814, two years after Laplace published the most well-known formulation of Bayes' theorem, which is exactly what the saying embodies.
Gah. Another crap submission from PhysOrg. This has been going on so long that many HN participants have called that out as a bad source before. PhysOrg appears to have been banned as a site to submit from by Reddit (according to what I've read here on HN). I learned from other participants here on HN that there are better sites to submit from.
The source was Eugene McCarthy from macroevolution.net. I took the time to analyze, weigh, summarize, and find a place to publish it. Physorg took it at face value from me, and published it.
Physorg took it at face value from me, and published it.
Well, now I understand why you seem personally offended by the call to weigh the evidence, which includes weighing the evidence that submissions from PhysOrg often have the Bozo bit turned on. The previous discussion in this thread already linked to a much better write-up on the substance of the issue
by a developmental biologist who understands and explains why this speculative hypothesis makes no sense. Read up more about biology before summarizing next time.
I'll let physorg handle themselves on that. I am sure you know more about their content history here on HN then me. Either way, your "crap submission" comment was to me so I responded, as you no doubt would yourself to a similar attack. You will be seeing a lot more science from me on physorg, and elsewhere, since I just got started http://hewitt123.com/blog/?page_id=45 Blocking it hurts your community here a heck of lot more than than me, so chill out and tune in. Pharngula made a nice composition, did his post start this thread? If he was honest he would have said what I did, biology and genetics can't prove or disprove this right now, and that is among the reasons I raised it for intelligent discussion in the first place. Until we can watch, and sufficiently understand, chromosomal translocations, pairings, matching, splittings etc. during meiosis/recombination, criticism from ignorance best shut up and learn something. Professional scientists calling this guy an idiot, or pig, or saying, like pharygula, that this guys pants are probably full of semen, are those that you would be better served in blocking to improve this forum. Pharygula calls for an experimental cross between a human and swine, that's not even what was proposed here as an explanation of human origins.
"These days, getting a Ph.D. is probably the last thing you want to do if you are out to revolutionize the world. If, however, what you propose is an idea, rather than a technology, it can still be a valuable asset to have."
Man, those newspapers' opening lines are getting worse and worse...
The author seems to be a well-established scientist, and the arguments are quite plausible, given that this level of hybridization actually could be possible. What I find amazing (based on the article) is that hybridization hasn't really been researched very well, and that hybrids aren't actually infertile, on the contrary to popular belief.
As the article points out, this indeed sounds as ridiculous as Darwin's proposal that humans descend from apes.
But and hybrid between a chimp and a pig: simply no way! Even creating a live pig-chimp hybrid is probably almost impossible, a fertile pig-chimp hybrid would be a miracle.
It doesn't matter that fertile hybrids are unusual. For evaluating this theory, it only has to be possible to produce a fertile chimp-pig hybrid. Then, given a large number of chimp-pig... interactions, you can then assume that eventually one would be successful.
(That said, before you interpret this as me supporting the theory, please read my top-level comment)
Nope, possibility is never enough evidence (disregarding likelihood). The old tale from thermodynamics: "Entropy tends to it's maximum. In reality there is a chance that all air in the room will concentrate in a small spot and entropy will decrease; how often did you see that happening?"
The problem is that those pigs and chimps that try to interbreed and fail would be wasting time and resources and end up falling behind in fecundity to their "breed true" cousins. Evolution would disfavor such behaviors as they would represent a vanishingly small percentage of the their respective gene pools.
Unless, perhaps, both particular species of ape and pig routinely had sex for pleasure (https://en.wikipedia.org/wiki/Animal_sexual_behaviour suggests it's possible), and just happened to cross paths. In this case, they're not really wasting resources as they would have been having non-reproductive sex anyway.
It's not just the "casual" contact time; for females, they would very often be wasting a reproductive cycle on a fetus that would (in the statistically significant majority of cases) self-abort.
This. The author makes the absurd claim that because many hybrids are fertile, any hybrid could be fertile. Using hybridization between two closely related birds to support the notion that pigs and apes could breed is ridiculous.
The scientist behind this hypothesis makes no such claim:
"For my own part, curiosity has carried me away from my old idea of reality. I no longer know what to believe. Is it possible that so many biologists might be wrong about the nature of human origins? Is it possible for a pig to hybridize with a chimpanzee? I have no way of knowing at present, but I have no logical or evidential basis for rejecting the idea. Before dismissing such a notion, I would want to be sure on some logical, evidentiary basis that I actually should dismiss it. The ramifications of any misconception on this point seem immense." --from macroevolution.net
He says it would be possible and there's evidence in physiology. Saying there's no way or that it would be a miracle (and dismissing it for that) is showing a misunderstanding of evolution. Given enough time and enough tries, it could happen.
A bacterium becoming a mitocondrium within a cell is one of the most astounding miracles of life and scientists have never been able to reproduce it (and mind you, generations of cells come by far easier and faster than of chimps and pigs), yet it happened, perhaps exactly and only once, but it happened and that's why all animals exist.
I think, like the author, that some curiosity and imagination is never a bad thing. It's led to our most interesting discoveries.
1 people think hybrids are sterile, but they're not
2 people think hybrids don't occur in nature, but they do
3 people think only plants hybridize, but animals do to
From this basis, he concludes that a chimp-pig hybrid is plausible, and proceeds to lay out his theory.
The problem is the three facts he starts with are trivial compared to the obstacles raised by PZ Meyer. To take just one, there is the difference in chromosome number. In most cases, if a human ends up with the wrong number of chromosomes, it's a lethal condition. Or you end up with Down's syndrome. With one extra chromosome. The hybrid this guy posits has a dad with 38 chromosomes and a mom with 48.
I could argue that that's not a big deal. In the plant groups I study stranger things happen. But that's in plants. Primates, as I understand it, are much more sensitive to chromosomal abnormalities.
There are many logical, evidential reasons to discount this hypothesis. Again, check out the pz meyer post linked elsewhere. Claiming I don't understand evolution because "given enough tries anything is possible" is facile. Of course anything is possible. But what is probable here?
I think we agree it's highly improbable, but then all major leaps of life and evolution have been. From that ground, I don't see why you seem to be angry at the guy for making a (minimally plausible, not because of the obstacles, but because of what the theory would explain) leap of faith and then wanting to prove his way there scientifically, tagging the whole ordeal 'absurd' and 'ridiculous.'
Sure the hybrid has parents wildly different genetically. But if two individuals who have a high chance of producing fit offspring may by chance produce unfit individuals, then we also agree the hybrid would have to have been a minimally fit individual by chance born from two parents who have a very low chance of doing so. A person with Down syndrome is not a catastrophe of nature, and not fundamentally a disease, such that through successive backcrossing (women with Down syndrome are usually fertile) it could theoretically produce a different kind of Homo that would be fit for some imaginary environment conditions. Or at least would still be a far more intelligent creature than all other animals we have on this planet.
This bothers me as a former professor, because these fringe ideas undermine teaching and waste time. Imagine trying to present a lesson on evolution, and one of your students brings this up. You spend a few minutes discussing it. Of course, you've never heard of it before, because it's beyond implausible. So you spend your evening looking into it, and the holes in the theory. Next class you spend more time discussing it. If you're good, the student understands and you move on. If not the student leaves thinking this is a valid alternative viewpoint. And no, an idea does not become valid simply because it's not impossible. It's not unreasonable to demand more than a faint hope probability before judging an idea worth serious discussion.
This happens once, and you can make it a teachable moment. But when the scenario starts to repeat itself it undermines the effort you're putting into teaching real science.
Well that's an interesting point. There is survivorship bias. If the key event for life to thrive never happened, then we wouldn't be here to talk about it, but maybe some other world would have evolved intelligent life instead and they would be.
If you assume that a hybrid is necessary for intelligent life (which is a crazy, unlikely, implausible assumption, I know) then it doesn't matter if it only happens in one out of a billion worlds, on the one world it does happen in, there will be intelligent people around to talk about how unlikely it is.
Now maybe it's not so implausible. Pigs are some of the smartest animals, and something weird happened a few million years ago to jump start human evolution such a crazy amount. Still seems pretty unlikely IMO though, but I'll raise my probability estimate of it slightly.
The thing I find most depressing about these crackpots is that some otherwise productive scientist has to spend an evening debunking their nonsense. And it still doesn't stop.
I taught evolution for undergrads, and occasionally had to deal with these issues from students. It takes time to look into them, and no matter how thoroughly debunked the theory, some kids find them too irresistible to let go of. It undermines real education in the end.
What often distinguishes the crackpot from the visionary is whether they are eventually vindicated. The latter usually begins their career being perceived as the former.
This is a tautology. Of course visionaries are the ones who were vindicated.
That doesn't mean that being perceived as a crackpot is a reliable indicator of being a visionary. It's similar to the argument that opposition equals confirmation -- some religious groups and conspiracy theorists argue that the fact that people oppose them means they are right.
I never said crackpots are guaranteed to be visionaries, though I'm sure it made a convenient strawman for you to argue against. My only point was that you can't be certain either way a priori, to be sure you must actually investigate it (and history tells us even then that's not always going to guarantee certainty).
The depth of investigation should be proportional to the probability of correctness, weighted by the cost of being wrong. Crackpots are called such because the probability of correctness is very low.
Given all the evidence, I consider the MFAP origin hypothesis to be significantly less likely than the primate evolution theory. Extraordinary claims require extraordinary evidence.
to play devil's advocate: consider the extreme absurdity of einstein's theory of relativity, the theory that time may speed up or slow down depending on your velocity.
> some kids find them too irresistible to let go of. It undermines real education in the end.
Teaching is not my cup of tea but isn't an important life lesson teaching kids how to smell bullshit? If they can do that, surely they will know what books to pick and what to learn.
True, to a point. Debunking one of these in a class is a good exercise. Preparing a lesson takes time, though, especially when you have to respond to something out of the blue. You could easily get caught spending all your limited spare time discussing why these theories aren't science, instead of the ones that are. Evolution is a big topic, and I'd rather spend my limited time dealing with the substantive bits.
Agree. Debunking this sort of thing would be a fabulous way of describing all manner of genetic principles, particularly the structure of chromosomes, recombination hotspots and haplotypes.
While the hypothesis itself seems rather unlikely, I think the evidence is interesting enough that further investigation would certainly yield some interesting results in their own right.
Major leaps in scientific thinking can often start with some pretty radical albeit erroneous ideas. But even if not true, these ideas can encourage a fresh perspective and a new approach for teasing apart the observable world.
This. It seems pointless to me to proceed with so much hand wringing and "my science-peen is bigger than yours" posturing, when we have ample opportunities (and plenty of pigs and bonobos) to test the hypothesis via experiment. Isn't that sort of the next step in a fairly tried-and-true method many here are usually quite fond of?
Personally I think the odds of any meaningful success are extremely low, but the cost to explore and experiment are also quite low. I'd rather trust "we attempted insemination of {x} bonobos with {y} varieties of pig sperm, but failed to achieve impregnation" (... or succeeded, or whatever) - over "I'm really smart, and trust me - this couldn't possibly work."
This is highly unlikely origin story. The main problem is that genetic data strongly and consistently suggests we are further from pigs than chimpanzees are.
Genetic material often finds ways of crossing species boundaries: in lower organisms, horizontal gene transfer is commonplace. But, this is just not supported by any scientific evidence.
I believe he addresses that by suggesting backcrossing with the chimp line. Still seems extraordinary such a cross should originally be even remotely viable.
My gut feel is that this is bat-shit crazy, but wouldn't it be amusing to see the response from the Jewish and Islamic world should it turn out that humans are pig hybrids? ;)
The broad (though not universal) taboo against eating primate meat has some basis in the higher risk of shared/cross-species diseases, due to a closer genetic relationship.
If there's a little pig in us, that'd argue for stronger taboos against eating pork... exactly as in Judaism and Islam.
Yes - I think many religious taboos have their basis in sensible food hygiene and incest avoidance. But that's not how it's pitched; often the claim is that "pigs are unclean".
Hybridization is actually a pretty interesting hypothesis for species differentiation in higher vertebrates, given that generations are often very long, hindering traditional accounts of evolution-through-mutation.
Recombination occurs very time a new sex cell is produced during the crossing over event, Dawkins dispels the random mutation as the only means of genetic shift very early in his book "The Selfish Gene" as the crossing over process can split chromosomes mid-gene for longer, more complex DNA sequences.
Jean Auel's The Clan of the Cave Bear book-series explores the possibilities of Neanderthal/Cro-Magnon interaction, but this article brings up a whole new set of intriguing plot twists.
So far, there are two proven gene-flow events to Homo sapiens from non-sapiens: Homo neanderthalensis and from the Denisova hominin population. In the latter case science isn't sure yet whether the Denisova hominin was a sub-species or species.
We probably got some immunity-related genes from neanderthals, but probably not red hair - red hair in neanderthals is caused by a different mutation that doesn't exist in humans.
Do we have a designed ornithologist here to comment about the book?
My guess is that all the cases in the book are hybrids between very related bird species. For example, in the PowerPoint presentation, there is a hybrid between two types of crows, other cases are not so obvious, but IANAO. But I didn't see any hybrid between two obvious distant species, for example between an ostrich and a stork.
A simple way to define a 'species' is any group of creatures that can produce viable, fertile offspring.
So dogs are breeds - they're part of the same species - because if you mate a great dane with a chihuahua, you'll get a fertile dog (I believe; if you plan to experiment, I recommend the chihuahua is male and great dane is female). If you're lucky, that dog will have desirable characteristics that may one day end up being the parent of a new breed.
But horses and donkeys are not breeds - they're different species - because if you mate them you get a mule which is not fertile (a hybrid, therefore).
In the end, this definition is a bit too simplistic because it's not necessarily always so clear-cut. Hence the article here :)
I would expect that a "breed" should also be stable. That is, pairings between male and female members of the same breed should produce offspring of that same breed nearly every time.
Your remark "I recommend the chihuahua is male and great dane is female" is interesting, but how true is it? Has anyone experience? Is it harder for a small female dog to bear puppies from a big male dog?
Interestingly, this very same hypothesis was the basis for a novel by french author Bernard Werber called "le père de nos pères" (the father of our fathers), published in 1998.
I actually find this plausible. Like the author I also have problems believing that random mutation and selection is a complete/adequate explanation. Just a hunch, there's a deeper theory to be had here.
1) A hybridization event indeed occurred in the relatively recent genetic history of homo sapiens (rather than the unusual anatomic features being produced some other way).
2) The hybridization was with a close relative of pigs (rather than another family that has some similar characteristics, or multiple hybridizations that together gave us the unusual characteristics).
3) The hybridization marks the point at which hominids split from the other primates (rather than occurring later in one branch of the hominid family tree).
4) That the genes introduced by hybridization gives hominids their unique characteristics (rather than being inconsequential).
In return, the theory presents evidence (anatomic oddities and low fertility) that I would characterize as "interesting" and perhaps "worthy of further study", but certainly not extraordinary. For this to be plausible, there needs to be a second avenue of evidence, one not based on anatomic similarities...
That second avenue could be genetic, but they specifically dismiss it, presupposing a mechanism, backcrossing, that leaves little genetic evidence that it occurred. Now, I'm no geneticist, but that sounds a bit fishy to me.