LD: The Neanderthal data is puzzling, but it’s still pretty tentative. I think we only have about 4 data points at this time. I don’t think you could find any large mammal with lifespans comparable to humans that would fit this pattern-- ie, two populations that diverged .5M years ago but that were not cross-fertile. And we have many known instances of mammal populations that diverged longer ago than humans and chimps diverged, and that ARE cross-fertile. There’s probably more to this puzzle than we know about now.
But you are correct, in that the genetic data we **do **have does not support the idea that chimps and humnas can hybridize. We can still hope, though, can’t we?
Baboons are monkeys, not apes. I think the human and monkey line diverged about 40M years ago. I would be VERY surprised if humans and monkeys were cross-fertile.
I don’t really want to hijack this thread too much Loopydude but that argument is completely wrong. We have the same evidence for example that the earliest humans in Australia some 50, 00 years ago did not contribute to the current human population. However these individuals were indisputably H. sapiens and perfectly interfertile with H. sapiens. Likewise these individuals had frequent opportunities to mate with other human populations.
The point is here that these early Australians left no offspring not because these first Aborigines were insufficiently genetically compatible to produce offspring” but simply because they constituted a dead end branch of the human tree. The same is almost certainly true of Neanderthals. Be very careful about drawing unwarranted conclusions from genetic tests. The tests do not indicate any lack of interfertility or interbreeding between the two species ion any way. All they indicate is that the Neanderthals, like the Australians, left no female descendants for whatever reasons. As we get more DNA samples form more ancient human populations we will probably discover numerous such dead end branches on our tree.
Certainly the genetic evidence from Neanderthals neither supports or rules out human chimp hybridisation on bit. But enough of this hijack. You can start another thread on this topic if you wish, but this debate assumes that such hybrids are possible.
Well no, because if these individuals are deemed to be legally human then I have no more legal or moral right to make such demands and accusation than I have to demand birth certificates to prove the kid isn’t Japanese or accuse someone of having an affair with a Negro.
That’s why the real heart of the question is where we draw the line between human and animal for such hybrids.
Jeez in the time it took to make that post the thread has turned into a massive hijack. Please people, the OP assumes that such hybrids are possible and have been found to exists.
I’ve started another thread for those who wish to argue whether they are possible but can we not hijack this otherwise interesting topic with a debate about whether a hypothetical situation is scientifically possible?
This debate on what effect hybrids would have on our society is worthy and interesting in itself as is the scientific debate about whether such hybrids are possible, but they are totally different and unrelated subjects.
Well, Blake, those caveats are all entirely valid, but when you look at likelihood, it’s difficult to argue that all the possible dead-ends simply vanished, given the enormity of the overlapping human and Neanderthal habitat. Australia is a relatively isolated landmass off the Southeastern tip of Asia. Certainly human migration occurred into and out of the Australian continent; but contrast Australia with Europe and especially the Middle East, which is at the confluence of three continents. To quote the article I cited: “‘There is still a remote possibility that only nuclear DNA was contributed, or that any Neanderthal mtDNA lineage has been lost during human population bottlenecks in the last glacial max, but the odds appear pretty slim,’ said Cooper.”
Sorry! No more discussion of that. I just figured it was a germane point of discussion, as it related indirectly to the potential for viable human/great-ape offspring.
Irrespective of what the potential is, the OP assumes that the hybrids exist. Now we want to know what they might be like and what effects their existence might have. Even if the potential for their existence is only one in a trillion the OP assumes it’s been overcome.
Well, what do we know about other chimeras that are extant? For instance, here is a regerence to ligers. I never would have guessed that such a hybrid would be so much larger than either of its parents. Also, there are tigons. It would appear that, depending on the sex of either parent, the traits of the chimera (liger = male lion+female tiger, tigon = male tiger+female lion) can differ. That’s another thing I didn’t know until I did a little googling, though I probably shouldn’t be surprised; the sex chromosomes could be quite different between the species.
So, to extrapolate a bit, if, say, a male bonobo (to pick perhaps a more permissive species) and a female human mated, you might get a girl bonuman (bonobo X+ human X), or a boy bonuman (bonobo Y+human X). The X chromosome in humans is a lot bigger than the Y chromosome, and this is probably also true of bonobos. The Y probably contributes little in either species to the overall genome except few genes mostly involved in masculine traits, as is true of humans. I would expect, then, that for the sex-linked traits, the boy bonuman is quite likely to be to some degree more “human” than “bonobo”. However, with the girl it’s more difficult to predict. In human girls, either the paternal or maternal X chromosome is “silenced” early in development. X silencing is mediated by the “painting” of one of the X chromosomes with the RNA product of the Xist gene, and how that gene behaves is quite a species-specific thing. How or if X silencing would occur in a bonuman is hard to predict.
First off loopydude we aren’t discussing chimeara, we are discussing hybrids. Ligers aren’t chimaeras, they are hybrids.
Next point to note is that humans and chimps are incredibly close genetically, far more so than lions and tigers. That closeness means that you can’t say that males will be more human than females. The sec chromosomes are fairly small anyway, but with such tiny differences involved it may well be that the Y chromosomes are 100% identical between species whereas the X are only 99%, in which case the males could well be more human. And of course it may well be that any differences on the sex chromosomes are so superficial that there would be no detectable phenotypic difference at either way.
Secondly in most women different cells have different X chromosomes disabled. Women are mosaic creatures where, for example, the upper portion of the left arm may be different genetically to the right arm or the lower portion of the same arm. However as you can tell it make very little difference to overall development and would likely make little difference in hybrids either. The X chromosomes simply don’t; affect any important developmental patterns.
And yes, this disabling of one chromosome would occur in hybrids. It’s not something that is easily altered.
Thank you for trying to keep this discussion on track, Blake.
I’ve not posted anything other than the OP because, despite my interest in the topic, I don’t think I have the necessary knowledge or debating skill to argue it intelligently enough so I appreciate your attempts to keep it related to its original premise.
Hmm. I’ve seen the term used interchangeably for tigons and ligers, perhaps because of appearance. If you want to be biologically pedantic, a chimera is a combinaiton of cells from two different embryos, either of the same or different species, that is true. Again, these animals are also called chimeras, for whatever reason.
The “incredible closeness” is in the coding sequences of human and ape genes. Major divergences can be seen in the regulatory sequences (promoters, 5’ and 3’ untranslated regions of mRNAs, and perhaps alternate start codons and splicing patterns), as is usually the case between species, and those differences are extrememly important. They must be, or humans and chimps would be much more alike. In fact, those divergences are a major focus of research right now, as these genotypic differences can tell us a lot about phylogeny, as well as the “language” of promoters, which is far from being decifered, at present.
I’m not so sure. The X chromosome contains roughly 5% of the genome, making it proportionally as important as any other chromosome. So, again in my example above, in males, 5% of their genome would be exclusively human (as I said, all X-linked genes are now human), where in females, it would be a mix of unpredictable proportion. In mice, at least, if the male X chromosome is not silenced in some parts of the embryo, the placenta doesn’t develop properly, and the embryo will not survive. Also, X imprinting is a random process, but occurs early in embryonic development, again by action of Xist. After that, there is a kind of memory, mediated by methylation or other mechanisms, which propagates in the somatic descendants of those early embryonal cells. Anyway, this whole process can differ from species to species. I suppose this is going to be a lot closer between chimps and humans, and mice and humans, but it’s not an easy call, if you ask me.
I doubt very much if they are called chimaeras by any reputable sources.
But if the embryos don’t survive then it’s a moot point. You seem to be drifting back to the same hijack. We are working here with organisms that have successfully produced offspring.
It’s called “scanning” , which is my euphamism for “not reading the entire thread carefully”.
I’m still intrigued by the differences due to parentage. X silencing is one possible mechanism, but then again, if the phenomenon is random in all somatic cells, why should it matter in females? One guess is it’s not entirely random, but I haven’t the time to research it right now.
And you decide? If it’s a custom, that would trump technical accuracy in the real world. Suffice to say, pedantic nitpicking of my word usage (as if it makes a point or I don’t recognize the differences) is an irritant, as well as is Jr. Mod-ing.
Use some imagination. That’s the point of this thread, no? I provided an example of other-than-random X silencing during embryogenesis. Are there other possibilities? It also appears that paternity is reflected in phenotype, even if the offspring are female. Why is that? Could X silencing play a role? It’s already been demonstrated there are species-specific differences in the phenomenon. I made the point merely to point out it’s not an easy call. Per the OP: “[W]hich species would it most likely take after?” It seems to me such wild-arsed speculation is germane to the discussion. If you want to simplistically discount all my points, and then add injury by labelling anything I say a “hijack”, may I request in return you butt out and leave that to the OP?
I for one think that a bonobos crossbreeding program is the best hope for humanity… no more bar fights - only bar orgies.
To be fair Blake, some discussion of the viability/vitality of the “new breed” has to be pegged down or pondered. How many rights they’re eventually granted will probably depend on how much of a “real human” they are in the eyes of umm, real humans. I could see a stratification of rights if, as in the case of ligers, the females could re-enter the stream and intermarry/bear children but males were born sterile.
Though that’s all probably after mental ability considerations.
