What makes Neanderthals so interesting is they split from sub-Saharan humans long before what we now call modern humans evolved. That and the fact they still walk amongst us - everyone who is not of sub-Saharan decent is part Neanderthal.
Has this been proven? I mean both conditions, ie: that everyone of sub-Saharan descent having no Neanderthal DNA? Also, the percentages are really low, eg: my friend from China did 23andme and his Neanderthal percentage was 0.1%.
There are also people that have far more than the average (2-3%) - for every person like your friend there are other with way more.
What does it mean to be a separate species if you're interbreeding in a significant way?
What does it mean to have n٪ Neanderthal DNA if that DNA is found in a significant proportion of "modern humans"?
As for what it means if some of us have Neanderthal DNA and some don’t is some of us are a hybrid species [1].
Species is a squishy concept. You might be amazed at how much intense arguing that continues to be about what delineates two closely related species. I think it's hard to consider Neanderthals a separate species, given what we now know thanks to ancient DNA. I think the term sub-species makes more sense.
> What does it mean to have n٪ Neanderthal DNA if that DNA is found in a significant proportion of "modern humans"?
It means that before the point at which the lineage that we call "humans" interbreed with the lineage that we call "neanderthal", these particular pieces of DNA were found only in the neanderthal lineage.
I admit my sort of base assumption is that simple quantitative metrics such as n% African/n% Neanderthal peddled by the likes of online genetics testing labs are grossly oversimplified at best and probably borderline meaningless at worst...
Regarding ancestry testing: it’s pretty valid, in general. DNA extracted from ancient human remains has completely revolutionized our understanding of recent, ancient, and extremely ancient human history. The online testing companies use the same methods and data sets. The way they present results boils a lot of different stuff down to a single number, so nuance and some fidelity is inevitably lost, but that’s always an issue when you try and make a nuanced subject understandable to laypeople. But, generally speaking, if an online test says that your DNA is 5% Neanderthal whereas someone else’s is 1%, or that you’re 20% Western European and 40% Eastern European, that is probably a valid way to present things.
If 'Neanderthal DNA' is found in a huge percentage of 'modern humans', on the face of if, it seems to me the notion that Neanderthals should be considered a separate species is the preposition that seems somewhat/increasingly spurious...
There is evidence that the offspring of the Neanderthal hybrids follow Haldane's Rule [1].
Yes, great question. Pheasants and chickens can breed and produce fertile offspring, along with many other combinations. Are they different species? Most say they are, but why given matching chromosomes?
They look dramatically different and are from different areas, true, but just like Native American Chihuahuas and Greek Harehounds, both which we claim to be dogs. They definitely don't look the same to me, or to most people.
As far as Homo Sapiens Neanderthals goes, well... yes, some still say that's actually Homo Neanderthals, but a lot now agree it's not really a different species. Source of quite a few bitter fights in academia though.