I know that we don't all have the same sense of humour but rgrieselhuber did not deserve to be DVd. I will accept that their comment was not exactly useful but it could be construed as funny.
This happened a mere 5,000 generations ago... (before the separate admixture with European and Melanasian Homo Sapiens).
Were the Denisovans as different from Neanderthals as Sapiens were from either branch? †
Reading the branch/tree diagram it looks like only Europeans mixed it up with the Neanderthals, after splitting from Asians, and only Asians with the Denisovans, also after the split. Meanwhile Africans never encountered or mixed with either of those ancient hominid branches. Our ancestor branches and genome are so varied and rich!
† "Denisovans and Neanderthals split from Homo sapiens around 744,000 years ago and diverged from each other 300 generations after that."
That is not quite right - Asians actually have more Neanderthal genes than Europeans. The current best hypothesis is that there have been multiple Neanderthal/SSA hybridization events and that some occurred post the split between Europeans and East Asians (the first occurred in the near East and later events occurred in East Asia).
How would they know they are different species? They don't have their DNA. The Denisovans are just a different form and we don't find them outside one cave. And now they claim that different species can interbreed? Who determines all this?
Whether Denisivans and Neanderthals are different species is mostly just a matter of semantics. We have had a pretty good look at the DNA of each and it's clear that the two were evolving in isolation for hundreds of thousands of years resulting in genetically distinct populations. The difference between Denisovans and Neanderthals is about half the difference between humans and either.
It's not at all unusual for two different species to be able to interbreed. Lions and tigers for instance or horses and donkeys. Mules, the offspring of horses and donkeys are sterile, though, so the two populations can't mix. Ligoers, the offspring of a male lion and female tigers, aren't entirely sterile but have very low fertility. With humans and neanderthals there are portions of the Neanderthal genome related to reproduction that were very heavily selected against in a way which seems to indicate that male hybrids at least had moderate fertility problems until those genes were removed. So it's not black and white at all. We have zero evidence for any reduction in fertility between Neanderthals and Denisovans since we have very few examples of hybrid offspring and this sort of analysis needs lots of data - so who knows.
One nitpick it is not male hybrids that had reduced fertility, but following Haldane’s rule it was the male SSA (sub-saharan african) and Denisovan/Neanderthal female offspring that were infertile - the other way around were fertile or else there would be no descendants of the Denisovans and Neanderthals living today.
That’s my point. We don’t know the amount of gene transfer between the two groups at different times. Calling something two different species usually implies some sort of allopatric speciation leading to almost zero gene sharing. Can you name a single proven example of something like this happening in the last few thousand years?
Yes we do have the DNA of Denisovans and Neanderthals (extracted from bones), but more importantly we have the living descendants of both (Eurasians in the case of Neanderthals and Melanesian/Australian Aborigines in the case of Denisovans).
The issue if Denisovans and Neanderthals are different species to sub-Saharan Africans is complex (nothing in biology is simple). Looking at the gene flow into existing populations it appears all Neanderthal and Denisovan genes came in via the male side. This suggests that the offspring were subject to Haldane’s rule [0], which is a strong marker for interspecies not intraspecies hybridization.
More importantly, the three homo populations fit all the criteria for being different species that apply to the rest of the animal kingdom (i.e. genetically isolation and genetic adaptation to different environments).
We should not forget that different does not mean inferior. Lions and tigers are different species of the genus Panthera, can they interbreed (Liger) and are subject to Haldane’s rule. Despite this one is not a better cat than the other.
To be more precise, there are actually only a few known bone fragments of Denisovans, so details about their morphology is not known.
You can tell that they’re different species by analyzing the DNA to figure out when the lineage diverged from a common ancestor with Neanderthals. In the case of Denisovans and Neanderthals, if I recall correctly, they diverged like 400k years before the specimens which have been found were alive. Whether that qualifies as a different species depends on how you define species. But the divergence is similar in scale to the divergence between humans and Neanderthals, so if you consider humans and Neanderthals different species, then Denisovans are also a separate species. The alternative is to consider then all different varieties of human.
Edit: just wanted to add this write up by Razib Khan for anybody interested:
(1) They do have the DNA... That's actually how this discovery came about, and the reason for all the progress in this field over the last few years. Svante Pääbo at the Max Planck Institute and his team invented a method to extract DNA from ancient bone fragments a few years back.
(@) The term "species" doesn't really have a definition in biology. You seem to be suggesting that producing offspring defines two individuals as belonging to the same species. That's not a workable definition because most life on earth doesn't breed at all. It's also not the correct, obsolete definition, which had always been "producing offspring that is itself fertile". Otherwise, tiger and lion are one species (producing infertile liger when they mate).
Ligers are not infertile and species does have a definition in biology. Where the argument comes about is if two different populations are different species or not.
Interesting how main stream science obsesses over Neanderthals but ignore Boskopoids. I suppose it does not fit in with the narrative being projected on humanity. Also worth mentioning Adam's calendar which was discovered in 2003 in South Africa and predates Stonehenge by 10s of thousands of years.
A quick Google suggests Boskop man was a modern human and Adam's calendar are 16th century livestock enclosures . . . so I'm really not sure what you are trying to say.
I hope this means you did not end up on all the crackpot sites that runs counter to any sane scientific approach and runs their arguments based on refuting existing research based on incompleteness and plain disbelief ? Do you have some credible information, or are they secret ?
No I have just found so many discrepancies on wiki through the years that I do not consider it a valid cite and many academics agree. Are you perhaps to lazy for more in depth research than picking the first hit on Google and forming your opinion based on that one source of information?
You are the one making extraordinary claims and complaining how "mainstream science" ignores them.
The burden of showing credible evidence clearly falls to you, and you have yet to show anything at all. I think you should already consider yourself lucky that some people have even deigned engage with you despite your tone and your general conspiracy theorist attitude.
Hmm, if you are so high and above most of us, why not contribute to the mankind and actually improve that wiki page with some cold hard facts in academic fashion? If you actually know them of course
35 comments
[ 2.7 ms ] story [ 86.0 ms ] threadWhy, HN, why?
Were the Denisovans as different from Neanderthals as Sapiens were from either branch? †
Reading the branch/tree diagram it looks like only Europeans mixed it up with the Neanderthals, after splitting from Asians, and only Asians with the Denisovans, also after the split. Meanwhile Africans never encountered or mixed with either of those ancient hominid branches. Our ancestor branches and genome are so varied and rich!
† "Denisovans and Neanderthals split from Homo sapiens around 744,000 years ago and diverged from each other 300 generations after that."
[1] https://en.m.wikipedia.org/wiki/Denisova_hominin
It's not at all unusual for two different species to be able to interbreed. Lions and tigers for instance or horses and donkeys. Mules, the offspring of horses and donkeys are sterile, though, so the two populations can't mix. Ligoers, the offspring of a male lion and female tigers, aren't entirely sterile but have very low fertility. With humans and neanderthals there are portions of the Neanderthal genome related to reproduction that were very heavily selected against in a way which seems to indicate that male hybrids at least had moderate fertility problems until those genes were removed. So it's not black and white at all. We have zero evidence for any reduction in fertility between Neanderthals and Denisovans since we have very few examples of hybrid offspring and this sort of analysis needs lots of data - so who knows.
One nitpick it is not male hybrids that had reduced fertility, but following Haldane’s rule it was the male SSA (sub-saharan african) and Denisovan/Neanderthal female offspring that were infertile - the other way around were fertile or else there would be no descendants of the Denisovans and Neanderthals living today.
0. https://en.wikipedia.org/wiki/Coywolf
eg https://www.ncbi.nlm.nih.gov/m/pubmed/3378453/
The issue if Denisovans and Neanderthals are different species to sub-Saharan Africans is complex (nothing in biology is simple). Looking at the gene flow into existing populations it appears all Neanderthal and Denisovan genes came in via the male side. This suggests that the offspring were subject to Haldane’s rule [0], which is a strong marker for interspecies not intraspecies hybridization.
More importantly, the three homo populations fit all the criteria for being different species that apply to the rest of the animal kingdom (i.e. genetically isolation and genetic adaptation to different environments).
We should not forget that different does not mean inferior. Lions and tigers are different species of the genus Panthera, can they interbreed (Liger) and are subject to Haldane’s rule. Despite this one is not a better cat than the other.
0. https://en.wikipedia.org/wiki/Haldane%27s_rule
You can tell that they’re different species by analyzing the DNA to figure out when the lineage diverged from a common ancestor with Neanderthals. In the case of Denisovans and Neanderthals, if I recall correctly, they diverged like 400k years before the specimens which have been found were alive. Whether that qualifies as a different species depends on how you define species. But the divergence is similar in scale to the divergence between humans and Neanderthals, so if you consider humans and Neanderthals different species, then Denisovans are also a separate species. The alternative is to consider then all different varieties of human.
Edit: just wanted to add this write up by Razib Khan for anybody interested:
https://www.gnxp.com/WordPress/2018/08/22/hominins-are-still...
0. https://en.wikipedia.org/wiki/Denisovan
(@) The term "species" doesn't really have a definition in biology. You seem to be suggesting that producing offspring defines two individuals as belonging to the same species. That's not a workable definition because most life on earth doesn't breed at all. It's also not the correct, obsolete definition, which had always been "producing offspring that is itself fertile". Otherwise, tiger and lion are one species (producing infertile liger when they mate).
Wikipedia wildly disagrees with you [1], it's few hundred years old
[1] https://en.wikipedia.org/wiki/Blaauboschkraal_stone_ruins
The burden of showing credible evidence clearly falls to you, and you have yet to show anything at all. I think you should already consider yourself lucky that some people have even deigned engage with you despite your tone and your general conspiracy theorist attitude.