Denisovans were a now extinct species of humans that were contemporaries of Neanderthal and that lived in a range from Siberia to Southeast Asia. Their genome has now been completely sequenced and, among other things, reveals that they had brown hair, brown eyes and dark skin. It also reveals that they interbred with Neanderthal and us. Per the article:
In addition, more Denisovan genetic variants were found in Asia and South America than in European populations. However, this likely reflects interbreeding between modern humans and the Denisovans' close relatives, the Neanderthals, rather than direct interbreeding with the Denisovans, researchers said....These current Denisovan findings have allowed the researchers to re-evaluate past analysis of the Neanderthal genome. They discovered modern humans in the eastern parts of Eurasia and Native Americans actually carry more Neanderthal genetic material than people in Europe, "even though the Neanderthals mostly lived in Europe, which is really, really interesting," Reich said....Comparing the Denisovan genome with ours confirmed past research suggesting the extinct lineage once interbred with ours and lived in a vast range from Siberia to Southeast Asia. The Denisovans share more genes with people from Papua New Guinea than any other modern population studied.
Wait, if Neanderthals and modern human interbred, wouldn't their offspring be infertile like a Liger? I thought that hybrids were always infertile, or am I just mistaken?
The offspring are not always infertile. Certainly significantly different species of dogs when interbred can produce fertile offspring. I suppose it depends on how different the species are. Per the article below:
....A small amount of that genetic mingling survives in "non-Africans" today: Neanderthals didn't live in Africa, which is why sub-Saharan African populations have no trace of Neanderthal DNA....
Well, I guess if the two species are closely related enough, such as when they're insame genus and share a very recent common ancestry (as in Homo Sapiens and Homo Neanderthalensis), than hybrids of the two specie could be fertile. But back to the above article, where does this place the Denisovans on the human family tree? Are they an entirely new species or rather a subspecies of an existing one, such as Neanderthals
My understanding is that they are supposed to be a distinct species but closely related to Neanderthal. My understanding is that they were more closely related to Neanderthal than to us. However, some of their genes are supposed to exist in some of us and so it seems that they were closely related enough to us to interbreed with us.
It could very well be true that female Neanderthals had difficulty passing their X chromosomes to hybrid offspring involving modern partners because, according to the article of this discussion, Denisovans (which were closely related to Neanderthals) produced a disproportionately low X chromosome gene pool in our population. Per the article:
Intriguingly, comparing the X chromosome, which is passed down by females, to the rest of the genome, which is passed down equally in males and females, revealed "there is substantially less Denisovan genetic material in New Guinea on the X chromosome than there is on the rest of the genome,"researcher David Reich at Harvard Medical School in Boston told LiveScience. One possible explanation "is that the Denisovan gene flow into modern humans was mediated primarily by male Denisovans mixing with female modern humans," Reich said. "Another possible explanation is that actually there was natural selection to remove genetic material on the X chromosome that came from Denisovans once that entered the modern human population, perhaps because it caused problems for the people who carried it."
I have read that when considering extinct races it is difficult to set a clear demarcation on whether they are a distinctly different species or not. If humans and Neanderthals interbred it suggests that differences between the two involved a genetic distance that while noticeable was not insurmountable.
Regarding skin colour, I have read that some researchers think that fair skin, hair and eye colour evolved fairly recently, say in the last 30,000 years or less. This paper argues that variations in hair and eye colour among Europeans were mainly due to sexual selection, as people with say blonde hair and green or blue eyes had a distinctive appearance that made them particularly attractive.
This might be true because native Asians of Northern Siberia nonetheless have dark hair and eyes. That is, the cold climate there did not induce lighter hair and eyes. However, people with lighter hair and eyes do have the advantage in a cold climate of getting more Vitamin D from the sun. Therefore, this might also have had something to do with its occurrence in Northern Europe. However, again this did not induce lighter hair and eyes in Northern Siberia.
Yeah, that's what people don't understand, when they only learned about Evolution from their fundamentalist preachers who have an agenda to keep them ignorant. The same gene that saves your life in one climate will kill you in another climate. There are very few variances in the human genome that are 'better' in every situation.
Dark skin decreases your chances of skin cancer, in a more equatorial climate. Pale skin decreases your chances of dying of rickets, in a more polar climate.
This is a very interesting topic. Let me first say I am not aware enough of the science to venture on using the correct terms. I probably understand them, but won't risk using them, as a layman.
However, when you consider the visual differences between the present "races" and the fact that this means very little at all, if anything at all, to the viability of our off-spring, and then you consider what we know about the visual differences of Neanderthals and Cro-magnons, it makes one wonder where exactly you can draw a iine between populations that were contemporary.
If they could breed together, could they be considered separate species at all?. Are they not just one species wildly variant in superficial ways?. It is interesting, and I wish I had more time to learn about it in depth.
I don't know that much about it either. I suppose they should be considered different breeds (for lack of any other term that comes to mind) of the same species just as there are different breeds of dogs that can produce hybrid offspring. I agree that an interesting question is that of how far back in archaic human examples one can go and still find some that could have interbred with us. Thinking out of the box a little (or a lot) I think eventually, and probably illicitly, archaic human examples will be cloned and then, for whatever the reasons, will be desired by modern humans as marital partners.
Yup. One thing you learn when you mix with any of the humans, is that they have a roving eye like mice have a cheese fetish.
*70 000 year old grandmama by way of what might even be another species*
"Why, helloooo there Nanna . . . wanna bump uglies?".
( sorry. lol )
Looks are almost not an issue with people, of course. Some of us find it more compelling than otherwise, a large difference in superficial appearence. I guess we will never know just how far back we were "human" enough that someone from then could make humans with someone from now.
Exactly so. If they ever shared a cave I am thinking they would first have to have considered each other somehow "people".
Stranger things have happened of course. One thing I know as a life long fisherman, is you can meet up with someone else who is fishing, and you don't need language, or anything like a common culture for the other parts of your life, you have an instant kinship of fishing.
With hand signals and smiles you can swap ideas of surprising complexity about the sport, with someone who you could not even find out where in the world they are from with words.
I remember meeting two blokes from one of the French speaking parts of Africa, we couldn't do more than swap names, verbally. Yet we fished together side by side for a morning, laughing, joking and trying to interact and showing one another our tackle :P and in the end I would have let them come back to my campsite for sure, even if we had been different flavours of caveman.
I think probably the C.Manon and Neanderthals had a lot more in common than they did different.