A geneticist who has made a career out of studying hybrids has proposed a shocking theory that accounts for our numerous and often dramatic differences with other primates. We may not be purely primates at all. We may, in fact, by a hybrid of chimpanzees (most of our ancestry) and pigs, with the resulting cross having back crossed to chimpanzees.
Like Darwin, before proposing such a controversial thesis, he has amassed an extraordinary amount of evidence, presented in dozens of pages on his web site. So before you consider the idea preposterous, read his site. I think you'll find the evidence rather compelling.
Boy it is tempting to take a comedy-central-meets- Andrew Dice Clay swipe at this comment. Seriously I know nothing of bio-genetics but it does seem peculiar too me. The only thread of which I know to this proposal is that there is a certain compatibility with pigs and humans for organ transplants.
I see you dwell in my most favourite country on the planet. I'm jealous!
There are so many compatibilities in our tissues - not just biochemically, but morphologically as well, that that's one of the pieces (among many) he cites for his hypothesis. This is one of the evidences which he explains in great detail. If you find the hypothesis just too implausible, I would suggest you read his web page. He's not just some wacko, he's a very serious scientist and has approached the hypothesis with rather considerable rigor. And as I noted, he's amply qualified in his discipline to discuss the evidence he presents.
Regards from a very rainy Costa Rica,
If Therians and Primates had successfully mated, there would be a huge gap in the fossil record, not to mention an indisputable mitochondrial linkage.
It is very easy to discover when two species had genetic contact. All you have to do is look at several of the genes the two species have in common, count up the mutations they do not have in common, and apply some simple math.
The fact that Dr. McCarthy didn't do these genetic tests is odd indeed, as it would provide indisputable proof of genetic contact between the sus and the homo lines. It's also striking that he did no genetic tests on the parasites he used to help support his thesis.
It is also telling that he didn't do any original research. He's quoting a lot of other people's work, but he has done none of his own. He uses only Inductive Reasoning to support his conclusions, which is not considered 'science'. Science is the use of Deductive Reasoning and Predicate Logic, combined with experimentation and original research to develop strong, falsifiable theories. He's done none of this. The tests necessary to debunk his claims (or lend them enormous credibility) are quite cheap and easy to do. If he has any confidence in his theory, he would spend the several hundred dollars necessary to do the preliminary tests. Positive results would get him air time on more than "Jimmy Kimmel Live" and would probably result in him winning an Nobel Prize.
He simply hasn't put in the work to justify publishing his theory. Considering all the time and effort he's gone to, it's far more likely that he doesn't even believe what he's saying and is just doing it to get attention. Interesting read though. He sure does know a lot of facts about hybrids, and I actually learned a few things reading his work. Not what I would call a good use of my time, but it didn't really take that long either.
That one's not a refutation of evidence as much as it's simply an emotional reaction and a diatribe. Hopefully someone can do better than that.
With regards to the nuclear genome, he discusses that at some length in a sidebar on the first page, in which he is pointing out that 'genetic conversion' would erase the evidence after a few generations of back crossing. With regards to mitochondrial DNA, since that is always passed down matrilineally, without recombination, he suggests that the original hybrid(s) were the offspring of a boar mating with a female chimpanzee. In which case the boar's genetic contributions would not include mitochondria. If that is the case, mitochondrial evidence would have nothing to offer, and we would have to rely on nuclear DNA for any genetic evidence. But the problem there, as he points out, is genetic conversion happening hundreds of times since, thoroughly erasing the evidence.
In the absence of entire donated chromosomes, as in the case of the platypus, recombination means we have a tough row to hoe to discern any damning genetic evidence for this theory. It will be interesting to see how it plays out in coming years. Yes, it's a revolutionary theory, and I suspect that more than a few scientists would love to spend some time in the research lab testing it. But it is so controversial, that it may have to wait - just as social research on the societal effects of religion had to wait until Creighton University finally broke the ice. As Thomas Kuhn noted, science marches forward, funeral by funeral - and those funerals are deans and research directors, more often than the scientists themselves.
Back crossing doesn't delete mutations that haven't happened yet. Back crossing is what keeps a genetic pool homogeneous. Once the two pools stop breeding, different mutations build up in each new, isolated pool. Back crossing can only obscure mutations that happened before the two pools separated. You cannot erase the evidence that hasn't been made yet. Mutations happen at a steady rate over time. Once backcrossing stops, the mutations in the two separate genetic pools will diverge. Simple math is used to determine when the two genetic pools separated.
Obfuscation, however well dressed up, cannot refute this simple point. It is not a revolutionary theory. It's a thinly veiled attempt to get attention.
As a biologist I view this theory as somewhat far fetched. However, much stranger theories have been posited that were at the time considered the ravings of a lunatic but ultimately proved to be fact. I would like to see some other biologist supporting the theory. Personally, I will keep an open mind - strange as the theory seems.
As you have said many times yourself extraordinary claims require extraordinary evidence. As such, in this case it would be necessary for someone to establish in no uncertain terms that a pig and a chimp are genetically similar enough to produce offspring in the first place. That is, in order for the idea to be considered less than preposterous a half pig half chimp offspring would either actually have to be produced or a chimp would actually have to become impregnated by a pig's sperm. If it is possible for a chimp to become impregnated by a pig's sperm it wouldn't be so very difficult to demonstrate. It should be demonstrable by artificial insemination. To have been scientifically coherent, research to the point that we are much more advanced than other primates because of hybrids between pigs and chimps should have started with establishing that such hybrids are at all genetically possible. The fact that the research not only didn't start this way but, from what I saw, all together evaded testing of whether a chimp could become impregnated by a pig's sperm when such testing would have been relatively easy suggests to me that the researchers are among the many sensationalists that call themselves scientifically oriented. Maybe they expected us to believe by faith that half pig half chimp hybrids are possible.
"...it would be necessary for someone to establish in no uncertain terms that a pig and a chimp are genetically similar enough to produce offspring in the first place."
That would require an experiment, and he suggests, rightly so, that there would be some ethical questions involved that preclude that experiment from taking place, except possibly in vitro. He himself reiterates the need to accept that extraordinary claims require extraordinary evidence.
He also addresses at considerable length the genetic incompatibility issue you raise. I think he addresses it quite adequately. With what part of his analysis in that regard do you have a problem?
As atheists, we frequently claim to look at hypotheses on their evidential merits, not on the basis of how emotionally appealing the hypothesis or its refutation may be. The latter is not science, it's religion. Let's look here instead at the evidence, not our emotional reactions to the hypothesis. Since he presents enough evidence, which is compelling enough, the hypothesis, in my opinion, is sufficiently supported to deserve further exploration and research.
There are no insurmountable ethical problems with in vitro fertilization and the creation of chimeras. We are already doing it with humans and mice, so doing it with chimps and pigs, just to show proof of concept, is a much smaller hurdle. Again, this entire argument is a farcical attempt to get attention.
I kind of agree with Carl here, (without the hurtling of accusations).
One could build an awesome, accurate model of a four-master tall ship without having a clue as to seamanship and mastering navigating in the oceans.