A chimp-pig hybrid origin for humans?
m.phys.org
m.phys.org
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.
All useful hypothesis are, by definition, extra-ordinary.
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.
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.
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.
Is there some evidence that the hairless trait was the result of human selection and no hairless varieties existed before human selection?
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.
Comments about PhysOrg:
http://news.ycombinator.com/item?id=3077869
"Yes Physorg definitely has some of the worst articles on the internet."
http://news.ycombinator.com/item?id=3198249
"Straight from the European Space Agency, cutting out the physorg blogspam:
http://www.spacetelescope.org/news/heic1116/ (press release),
http://www.spacetelescope.org/videos/heic1116a/ (video),
http://www.spacetelescope.org/static/archives/releases/scien... (paper).
"PhysOrg: just say no."
http://news.ycombinator.com/item?id=3611888
"The physorg article summary is wrong, I think."
http://news.ycombinator.com/item?id=4108857
"Phys.org is vacuous and often flat wrong."
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
http://freethoughtblogs.com/pharyngula/2013/07/02/the-mfap-h...
by a developmental biologist who understands and explains why this speculative hypothesis makes no sense. Read up more about biology before summarizing next time.
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.
"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?
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 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.
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.
(That said, before you interpret this as me supporting the theory, please read my top-level comment)
Stopped reading there. 'Consensus science' isn't science.
http://freethoughtblogs.com/pharyngula/2013/07/02/the-mfap-h...
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.
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.
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.
He had a lot of weight behind his claims.
"They laughed at Columbus, they laughed at the Wright brothers. But they also laughed at Bozo the Clown."
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.
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.
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."
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.
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.
Which is why it'd be funny.
Poor pigley.
http://en.wikipedia.org/wiki/Archaic_human_admixture_with_mo...
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.
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.
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 :)