Nature (2016) doi:10.1038/nature17405
Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins
Matthias Meyer, Juan-Luis Arsuaga, Cesare de Filippo, Sarah Nagel, Ayinuer Aximu-Petri, Birgit Nickel, Ignacio Martínez, Ana Gracia, José María Bermúdez de Castro, Eudald Carbonell, Bence Viola, Janet Kelso, Kay Prüfer & Svante Pääbo
A unique assemblage of 28 hominin individuals, found in Sima de los Huesos in the Sierra de Atapuerca in Spain, has recently been dated to approximately 430,000 years ago1. An interesting question is how these Middle Pleistocene hominins were related to those who lived in the Late Pleistocene epoch, in particular to Neanderthals in western Eurasia and to Denisovans, a sister group of Neanderthals so far known only from southern Siberia. While the Sima de los Huesos hominins share some derived morphological features with Neanderthals, the mitochondrial genome retrieved from one individual from Sima de los Huesos is more closely related to the mitochondrial DNA of Denisovans than to that of Neanderthals2. However, since the mitochondrial DNA does not reveal the full picture of relationships among populations, we have investigated DNA preservation in several individuals found at Sima de los Huesos. Here we recover nuclear DNA sequences from two specimens, which show that the Sima de los Huesos hominins were related to Neanderthals rather than to Denisovans, indicating that the population divergence between Neanderthals and Denisovans predates 430,000 years ago. A mitochondrial DNA recovered from one of the specimens shares the previously described relationship to Denisovan mitochondrial DNAs, suggesting, among other possibilities, that the mitochondrial DNA gene pool of Neanderthals turned over later in their history.
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5 comments:
I feel a bit of a déjà vu here, since we have already had this discussion.
Firstly, the majority of mainland European archaeologists would consider these specimen heidelbergensis, as has been done so for over half a century in the time from ~600,000 to ~350,000 ya (with some transition period from modern European erectus before then, and towards Neanderthal after that), and rightfully so as confirmed by later, detailed measurements and PC analyses.
Secondly, I had alredy pointed out with the previous mtDNA study, that this indicates heidelbergensis spread east early on (and later, ~200,000 ya, likely all the way to China), while the group remaining in Europe admixed with one from NE Africa via the African/Levant W Asian/ SE European triangle connection, and thus Neanderthals have a more "modern," i.e. more African mtDNA, while at the same time subsequent climatic isolation led to their peculiar accumulation of features (e.g., cold adaptations)..
"However, since the mitochondrial DNA does not reveal the full picture of relationships among populations"
Of course we've known that for some time. In fact it is surely taken for granted that each individual gene has its own evolutionary history. However mt-DNA does indicate something of population history.
"the Sima de los Huesos hominins were related to Neanderthals rather than to Denisovans, indicating that the population divergence between Neanderthals and Denisovans predates 430,000 years ago".
The earlier mt-DNA information showed Denisovans and Neanderthal/moderns split around 1 million years ago, if I remember correctly. That fits with the comment 'predates 430,000 years ago'. The same evidence showed Neanderthal/modern mt-DNA split around half a million years ago, which also predates 430,000 years ago. So by that time we have at least three branches of humans running around Western Eurasia and Africa.
"suggesting, among other possibilities, that the mitochondrial DNA gene pool of Neanderthals turned over later in their history".
The only conclusion possible I expect.
"the group remaining in Europe admixed with one from NE Africa via the African/Levant W Asian/ SE European triangle connection, and thus Neanderthals have a more 'modern,' i.e. more African mtDNA"
But there is no reason to accept that the Neanderthal mt-DNA line represents a separate movement out of Africa. The modern line may have entered Africa from Eurasia. In other words what we have is the coalescence of the modern/Neanderthal mt-DNA line, and even the distinct genetic pattern, somewhere within the Denisovan geographic range, possibly somewhere near the Levant. From where the modern line entered Africa and the Neanderthal line moved north into Europe, replacing the Denisovan line there. The Neanderthal a-DNA must have moved ahead of the Neanderthal mt-DNA, a situation quite possible especially if the gene flow was originally male-mediated.
Also, Neanderthal features first accumulated in W Europe, while E Europe, SE Europe and the Levant have a long history of showing less derived (i.e., more European erectus / heidelbergensis type) characteristics until late Neanderthal expansion, there.
So, there is no problem of heidelbergensis being both a progenitor of Neanderthals and modern humans, if the strong European gradient is taken account of: Neanderthals are derived from them, early on and in W Europe's isolation, while in SE Europe, SW Asia, and NE Africa, where we find a common development of bigger brains since late erectus (but not in E Asia), it appears that there was sufficient gene flow to have comparable features all the way to shortly before the appearance of AMHs.
"But there is no reason to accept that the Neanderthal mt-DNA line represents a separate movement out of Africa."
Terry,
I agree - my wording was a bit awkward, to say the least. We cannot at present distinguish the exact origin, except that fossil and tool and DNA evidence suggests significant gene flow between SE Europe, SW Asia, and NE Africa - perhaps making this combined region the cradle of AMHs.
The real question is divergence of Sima de Los Huesos from Homo Sapiens; with an age of 430,000 years, the beings at Sima de Los Huesos should be almost as ancestral to Hs as to Homo Neanderthalis.
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