Vol. 342 no. 6156 pp. 326-331
DOI: 10.1126/science.1238484
A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo
David Lordkipanidze et al.
The site of Dmanisi, Georgia, has yielded an impressive sample of hominid cranial and postcranial remains, documenting the presence of Homo outside Africa around 1.8 million years ago. Here we report on a new cranium from Dmanisi (D4500) that, together with its mandible (D2600), represents the world's first completely preserved adult hominid skull from the early Pleistocene. D4500/D2600 combines a small braincase (546 cubic centimeters) with a large prognathic face and exhibits close morphological affinities with the earliest known Homo fossils from Africa. The Dmanisi sample, which now comprises five crania, provides direct evidence for wide morphological variation within and among early Homo paleodemes. This implies the existence of a single evolving lineage of early Homo, with phylogeographic continuity across continents.
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12 comments:
"The Dmanisi sample, which now comprises five crania, provides direct evidence for wide morphological variation within and among early Homo paleodemes. This implies the existence of a single evolving lineage of early Homo, with phylogeographic continuity across continents"
Again I have been soundly criticised every time I have dared suggest that all H.erectus/habilis 'species' are a single species. In fact all human 'species' since that time belong to the one species and would be capable of hybridizing if time and space allowed. Here is what I wrote in an essay on the subject a friend put up in 2009:
http://humanevolutionontrial.blogspot.co.nz/2009/06/human-evolution-on-trial-first-point-of.html
"Caucasus Population
In the last few years fossils of half a dozen individuals, probably also ancestral to humans and dating to the time of Homo habilis (nearly two million years) have been found outside Africa. They lived just south of the Caucasus Mountains in Georgia and are associated with the same Oldowan stone technology. Like all other species on the human line mentioned so far they demonstrate a surprising level of variability (Gore 2002). In this case there seems to be no doubt they were members of a single species though. ... Lumpers regard all these different species as being just regional variants of Homo erectus. To and fro movement of genes goes back a long way in the process of our becoming human. Homo erectus may have been well named".
Agreed. Another crack in the facade of the Out of Africa theory, more circumstantial evidence in support of Multi-Regionalism. Out Of Africa only works if you insist upon a narrowly defined and highly constricted definition of the human species.
I thought it was pretty much established consensus that Asian erectus, and also the Dmanisi examples, branched off African erectus/ ergaster very early on, basically just when that one can be distinguished from habilis. So, at that time we have 2-3 slightly different looking groups in Africa; rudolfensis IMO isn't all too well defined. Since these appear to have lived contemporaneously for a while, there is little surprise that the first examples outside Africa also show some variety.
Still, there are clear and pretty large distinctions between habilis and erectus/ ergaster. In Europe, the "proper", more narrowly-defined erectus appears later, when it is also much clearer formed in Africa (ergaster) and habilis is gone, there, and also includes Acheulean stone technology on both continents. So it should be quite clear that there were at the minimum two migrations ooA between 2 and 1 million ya, and of course likely also some back-migration.
Finally, when people throw around erectus dates of 800,000 to 300,000 ya, in most cases I would say it makes more sense to classify those as heidelbergensis, or on some heidelbergensis continuum, when outside of E Asia. Again, during that time morphologies in most of Europe (except perhaps Iberia with an early divergence towards Neanderthals), the Levant, and Africa seem to develop in unison (but not in E Asia).
"at that time we have 2-3 slightly different looking groups in Africa; rudolfensis IMO isn't all too well defined".
The position of this paper is that the variation within those several African species is no more than that between individuals of the single species from Georgia. I presume you've seen John Hawks' take, but in case you haven't:
http://johnhawks.net/weblog/fossils/lower/dmanisi/d4500-lordkipanidze-2013.html
"there were at the minimum two migrations ooA between 2 and 1 million ya, and of course likely also some back-migration".
Very likely to be the case. We can be fairly sure that human evolution, as with any species, was far from simple. But it is far more than just possible that all these various species of Homo were freely inter-fertile.
"during that time morphologies in most of Europe (except perhaps Iberia with an early divergence towards Neanderthals), the Levant, and Africa seem to develop in unison (but not in E Asia)".
Which strongly suggsts gene flow.
"Another crack in the facade of the Out of Africa theory, more circumstantial evidence in support of Multi-Regionalism."
No support at all in this study for multi-regionalism. John Hawks has a nice discussion of the implications of the paper.
And modern humans do have highly constricted genetic diversity. Finding an early homo erectus in Asia tell you absolutely nothing about migrations of modern humas.
I presume you've seen John Hawks' take...
Yes, I have, but I don't agree with some of the premise or conjecture. 100,000 to 50,000 years ago there were AMHs, Neanderthals, Denisovans, heidelbergensis (?), and erectus. Shortly after, only AMHs with very little admixture of the others.
It looks to me the same thing happened with the African (ergaster) and late European erectus. For a while, there where habilis and A sediba and early erectus living simultaneously, and the Dmanisi specimen suggest a related sort of variety migrated ooA.
But in the end, the easily-recognized, huge differences between the African groups proved important: only the proper erectus survived. So, even while these were not different "species" in the classical sense, and very likely interbred, this does not exclude that one line had made incredible progress that would prove to dominate the further evolution of mankind.
"John Hawks has a nice discussion of the implications of the paper."
I have not seen this, would you please provide a link to it?
"So, even while these were not different 'species' in the classical sense, and very likely interbred, this does not exclude that one line had made incredible progress that would prove to dominate the further evolution of mankind".
That sounds more than a little like the old Victorian economic viewpoint of 'survival of the fittest'.
From The new skull from Dmanisi
Fri, 2013-10-18 16:20 -- John Hawks
“If we look later in time, as early Homo existed within and outside Africa, we see the findings outlined by Lordkipanidze and colleagues, and by Van Arsdale and Wolpoff. This pattern of similarities cannot be easily explained under a model of bifurcating change. It implies some degree of continued dispersal and mixture. I expect that the dispersal and mixture were biased in direction, probably more moving out of Africa than back into Africa. The dispersal and mixture happened episodically, not continuously. But viewed within the time-averaged record of 500,000 years, the overall appearance was one of gradual concerted evolutionary change of a highly diverse metapopulation. It should go without saying that this pattern is multiregional evolution; but it is multiregional evolution with an especially episodic rather than continuous nature.”
This statement leads me to believe that Prof. Hawks is in agreement with my assessment of the significance of D4500 and the Dmanisi hominids in general.
"I have not seen this, would you please provide a link to it?"
http://johnhawks.net/weblog/fossils/lower/dmanisi/d4500-lordkipanidze-2013.html
terryt,
Thank you for the link but it does not appear to be functional.
Link is working now, thanks again. It is the same thing I already stumbled across and quote from above.
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