As I have mentioned before, people have been too quick to generalize about "modern humans in Africa" from the early anatomically modern humans of eastern Africa, forgetting that our focus on them has been an artifact of the good geological conditions for preservation in that area, and the resulting overwhelming scientific interest in the region.
But, eastern Africa is the periphery of Sub-Saharan Africa, and we are lucky to have new finds described from West Africa and elsewhere, as in this paper.
The PCA and CVA results are quite instructive:
I bet that a few years from now, we will look with amazement at the naivete of the passing Out of Africa orthodoxy that bundled all Africans into an amorphous category of "our ancestors in Africa". It is also becoming clearer that increased African genetic variation is, at least in part, due to the continent being home to multiple deeply divergent populations that persisted, in various admixtures down to the present.
The PCA and CVA results are quite instructive:
Symbols: Grey diamonds. Modern humans; Black up triangles: Upper Paleolithic modern humans; Purple up triangles: Late Pleistocene African and Near Eastern hominins; Red stars: H. neanderthalensis; Red squares: H. heidelbergensis (s.l.); Black squares: H. erectus (s.l.). Ellipses indicate 95% confidence ellipses for Neanderthals (red) and modern humans (gray).From the paper:
Modern human populations were characterized by more positive scores on PC 1, and there was only minimal overlap among their 95% confidence ellipses and that of the Neanderthals. The Middle-Late Pleistocene African specimens (LH 18, Singa, Djebel Irhoud 1 and 2) and the early modern human specimens from Qafzeh and Skhul fell in the intermediate zone between Neanderthals / H. heidelbergensis on one hand and modern humans on the other. Qafzeh 9 was the exception, falling on the positive end of PC 1 and close to Upper Paleolithic European specimens. The latter sample, which included some of the earliest modern human specimens in Europe (Mladec 1 and 5, Oase 2, Muierii 1, Cioclovina), clustered within the modern human range of variation, and not in the zone of overlap with the archaic specimens.Note a few things:
- the similarity of Qafzeh 9 with Upper Paleolithic Europeans; geneticists had better stop inferring that the Skhul/Qafzeh hominids were the "first Out-of-Africa that failed"
- the similarity of Qafzeh 6 with Upper Cave 1 from Zhoukoudian.
This is especially the case when Qafzeh 9 may be the earliest unambiguously modern human with no "ifs and buts", with Skhul and Qz6 following close behind.
In the conclusion of their paper, the authors mention another skull with archaic features, from Congo:
Thus our restudy of the Iwo Eleru cranium confirms previously noted archaic cranial shape aspects, and the U-series age estimates on its skeleton support the previously proposed terminal Pleistocene date for this burial. Our findings also support suggestions of deep population substructure in Africa and a complex evolutionary process for the origin of modern humans , , , , , , . Perhaps most importantly, our analysis highlights the dearth of hominin finds from West Africa, and underscores our real lack of knowledge of human evolution in that region, as well as others. As also indicated by restudy of the Ishango (Congo) fossils , Later Stone Age fossils from at least two regions of Africa retain significant archaic aspects in their skeletons. We hope that the next stage of this research will extend studies to the Iwo Eleru mandible and postcrania, and to comparative materials such as those from Ishango.
According to paper co-author Chris Stringer:
Hi Dienekes, Unfortunately PLoS introduced a typo in the summary regarding the date, which should have read ~11.7–16.3 ka. Everyone please bear in mind the analysis only covered the superior cranial vault, as there was no face - I discuss the results further in my new book The Origin of Our Species.
UPDATE: Chris Stringer video and more thoughts
PLoS ONE 6(9): e24024. doi:10.1371/journal.pone.0024024
The Later Stone Age Calvaria from Iwo Eleru, Nigeria: Morphology and Chronology
Katerina Harvati et al.
In recent years the Later Stone Age has been redated to a much deeper time depth than previously thought. At the same time, human remains from this time period are scarce in Africa, and even rarer in West Africa. The Iwo Eleru burial is one of the few human skeletal remains associated with Later Stone Age artifacts in that region with a proposed Pleistocene date. We undertook a morphometric reanalysis of this cranium in order to better assess its affinities. We also conducted Uranium-series dating to re-evaluate its chronology.
A 3-D geometric morphometric analysis of cranial landmarks and semilandmarks was conducted using a large comparative fossil and modern human sample. The measurements were collected in the form of three dimensional coordinates and processed using Generalized Procrustes Analysis. Principal components, canonical variates, Mahalanobis D2 and Procrustes distance analyses were performed. The results were further visualized by comparing specimen and mean configurations. Results point to a morphological similarity with late archaic African specimens dating to the Late Pleistocene. A long bone cortical fragment was made available for U-series analysis in order to re-date the specimen. The results (~11.7–6.3 ka) support a terminal Pleistocene chronology for the Iwo Eleru burial as was also suggested by the original radiocarbon dating results and by stratigraphic evidence.
Our findings are in accordance with suggestions of deep population substructure in Africa and a complex evolutionary process for the origin of modern humans. They further highlight the dearth of hominin finds from West Africa, and underscore our real lack of knowledge of human evolution in that region.