KNM-LH 1 and other Pleistocene African specimens, all of which are potentially sampling candidate populations for dispersals across and out of Africa during the Late Pleistocene (12–15, 50, 59), differ substantially not only from recent Africans but also from individuals drawn from Holocene LSA archaeological sites. KNM-LH 1 and other Pleistocene African specimens (found with MSA and LSA artifacts) are also distinct from most EUP individuals.Things are looking good for my Afrasian-Palaeoafrican admixture hypothesis which postulates that modern Africans are a mixture of "Afrasians" (a group of humans that also spilled over into Eurasia and/or back-migrated to Africa) and various groups of very divergent "Palaeoafrican" populations. In the context of this hypothesis, greater African genetic diversity is understood not as the result of a bottleneck of epic proportions during Out-of-Africa, but rather as a result of admixture between the two groups.
PNAS doi: 10.1073/pnas.1417909112
Late Pleistocene age and archaeological context for the hominin calvaria from GvJm-22 (Lukenya Hill, Kenya)
Christian A. Tryon et al.
Kenya National Museums Lukenya Hill Hominid 1 (KNM-LH 1) is a Homo sapiens partial calvaria from site GvJm-22 at Lukenya Hill, Kenya, associated with Later Stone Age (LSA) archaeological deposits. KNM-LH 1 is securely dated to the Late Pleistocene, and samples a time and region important for understanding the origins of modern human diversity. A revised chronology based on 26 accelerator mass spectrometry radiocarbon dates on ostrich eggshells indicates an age range of 23,576–22,887 y B.P. for KNM-LH 1, confirming prior attribution to the Last Glacial Maximum. Additional dates extend the maximum age for archaeological deposits at GvJm-22 to >46,000 y B.P. (>46 kya). These dates are consistent with new analyses identifying both Middle Stone Age and LSA lithic technologies at the site, making GvJm-22 a rare eastern African record of major human behavioral shifts during the Late Pleistocene. Comparative morphometric analyses of the KNM-LH 1 cranium document the temporal and spatial complexity of early modern human morphological variability. Features of cranial shape distinguish KNM-LH 1 and other Middle and Late Pleistocene African fossils from crania of recent Africans and samples from Holocene LSA and European Upper Paleolithic sites.
Link
11 comments:
Hhmm. Dont mean to sound negative, but studies discussing solely crania these days sound positively archaic.
@ mike thomas
agreed =)
the only information here that really caught my eye was the broad distrubition of recent modern cranias (which is already well known and accounted for by osteologists due to the plasticity of the juvenile human skull--changes on the magnitude of dog skulls can be achieved with ohysucal manipulation of the infant skull. it takes several generations of selective mother-son, father-daughter inbreeding in dogs to achieve this).
the RMH range covers pretty much the entire spectrum of EUP samples, but almost none of the african specimens: LPA, EMH, MPH, IOW (which is very young), this sample, KNM (young) and almost HOF too (not as young, but still young enough to cause one to pause). These are as different to RMHs as NEANDER and cluster with them.
also interesting that NEOAF, though within the RMH distribution, cluster in quadrant closest to dissimilar african and neanderthal samples, yet LSAs are more broadly distributed.
in other sciences, distribution plots like this, would lead the researcher to conclude that all RMHs are descended from either EUP or LSA. but, given that NEOAFs cluster near the dissimilar africans, that IOW is only 13kyo, and that both hof and knm lived within the EUP/lsa timeframe, the more conservative theory would be that lsa and EUP are the same people, and NEOAFs are introgressed relatively recently with a still extant african archaic.
determining whether eups came from an lsa precursor, or vice versa, has to be based on dna. so far, eurasia is proving to be the cradle of all humans but africans. which in most sciences would be seen as the more parsimonious theory of the two.
ps: biologists have known for some time that extreme intra-species genetic diversity is a function of disease resistence and pathological load, not which population of a given species is "older." african finches are more diverse than american fjnches, but they are not older, just subjected to greater pathological loads...nnot unlike african humans compared to other human populations. when will this "myth" die in human origins studies? it's not science at this poi t, it's religion. or at least dogma.
@ Mike Thomas
My thoughts exactly. This is 2015. Until there is autosomal data that has been uncovered, this study is not one that can be used to make any sort of inferences into African paleoanthropology.
Mike Thomas,
You gotta work with what you've got.
I don't see what the surprise is here, these early fossils don't resemble recent Africans, but the question is what samples did they use for recent Africans? As we have seen with the Kennewick Man in the New World, cranially he did not resemble modern native Americans but his DNA was typical of that of Native Americans. Since this sample is from 23,000 years ago I don't expect it to resemble modern Africans from the same area, but again, which modern African samples were used?
@Unkown: which modern African samples were used?
The list of samples is in the SI Table S2. RMH is:
"RMH Recent modern human samples
Bushman (n=82) South Africa
Zulu (n=101) South Africa
Dogon (n=99) Mali
Teita (n=83) Kenya
Egypt (n=111) Egypt"
Physical manipulation of infant skulls can indeed result in striking deformation of the skull, see the ancient Hunnic fashion of skull deformation for example. But such deliberate skull manipulation was rather the exception during most of the time of human prehistory. Also, it's easily discernible for anyone with some basic knowledge if skull deformation has been practised.
That said, the shape of the human skull is the product of genetic disposition, probably also epigenetic legacy, and environmental influences - like everything on human bodies is. It would be naive to think that skull shape has nothing to do with genes and that the skull is malleable like play dough. Also some traits are more heritable than others.
I come from a family with extremely variable skull shapes. That's most likely the result of variable genetic background, because the living conditions were similar for all, at least within each generation. At least I can't discern a connection between different living conditions (which certainly improved over time) and skull shapes in my family, with very different types of skulls appearing in all sorts of living conditions. Instead I do see genelogical ties connecting similar types of skulls across generations. That's why I always found this talk about completely malleable skulls and useless craniometric studies naive and unworldly.
Maybe you're just not in the lucky situation to have such genetic variance in your family.
Sorry for triple posting, I thought this might matter: When even brothers, born 1 year apart and grown up in the same family have very different skull shapes, then the reason can only be genetic, because their environment and nutrition was exactly the same. I've seen this sort of stuff. One with a Dinaric, short, not broad, but very high skull, with nearly flat occiput, the other with a well rounded occiput and a rather round, broad skull. And they have ancestors and cousins with similar skulls. It doesn't look to me like genes don't matter and it's all in the food and living conditions, that's nonsense.
Your brother might also have another hair color, but hair color in a POPULATION won't suddenly come on blond. Europeans have a variety of phenotypes even within families but they are not random.
I wasn't speaking of myself and my brother, but apart from that I agree.
Post a Comment