December 28, 2010

400-200ka dental remains from Qesem Cave

The authors present three scenaria for the unique set of features of their discovered teeth:
  1. A local Homo population associated with the local Acheulo-Yabrudian cultural complex
  2. Neandertaloid traits (shoveling and lingual tubercle) may suggest a pre-Neandertal population, however, these traits are missing in the younger Skhul/Qafzeh specimens and re-appear in the later still Neandertals from the region
  3. Presence of multiple taxa in the sample; surprisingly earlier samples appear to be smaller and more modern than later ones
It is hard to evaluate the importance of this evidence, and it'd be nice to hear the opinion of dental/anthropology experts; my personal take-home lesson is that the finds are discordant with a simple model of heidelbergensis evolving into Neandertals and smaller and more modern morphology arriving from Africa.

American Journal of Physical Anthropology DOI: 10.1002/ajpa.21446

Middle pleistocene dental remains from Qesem Cave (Israel)

Israel Hershkovitz et al.

Abstract

This study presents a description and comparative analysis of Middle Pleistocene permanent and deciduous teeth from the site of Qesem Cave (Israel). All of the human fossils are assigned to the Acheulo-Yabrudian Cultural Complex (AYCC) of the late Lower Paleolithic. The Middle Pleistocene age of the Qesem teeth (400–200 ka) places them chronologically earlier than the bulk of fossil hominin specimens previously known from southwest Asia. Three permanent mandibular teeth (C1-P4) were found in close proximity in the lower part of the stratigraphic sequence. The small metric dimensions of the crowns indicate a considerable degree of dental reduction although the roots are long and robust. In contrast, three isolated permanent maxillary teeth (I2, C1, and M3) and two isolated deciduous teeth that were found within the upper part of the sequence are much larger and show some plesiomorphous traits similar to those of the Skhul/Qafzeh specimens. Although none of the Qesem teeth shows a suite of Neanderthal characters, a few traits may suggest some affinities with members of the Neanderthal evolutionary lineage. However, the balance of the evidence suggests a closer similarity with the Skhul/Qafzeh dental material, although many of these resemblances likely represent plesiomorphous features.

Link

11 comments:

  1. My cursory opinion of the genetic and morphological evidence surrounding human origins is that many traits that we associate with 'modern' humans were variously interspersed throughout a widespread species of humans; there has only been one species (in the biological sense) since H. erectus, if not those mysterious 'hablines' as well.

    I just caught this paper today, and I'm no dental expert. But I would be very surprised if a population of modern humans (the Eve group) popped up in one region (Levant/E. Africa) and remained furtive until geologically recently. Can you tell I lean more toward the multiregional camp?

    PS I just read your blog for the first time, and from the few posts I've been able to see so far I rather enjoy it.

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  2. "there has only been one species (in the biological sense) since H. erectus, if not those mysterious 'hablines' as well".

    I think that is correct, and have though so for several years. The evidence this year of interbreeding between modern humans and what have been presumed to be 'other species' supports that conclusion.

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  3. I have long held that before ~ 400,000 years ago, genetic exchange between Europe, the extreme SW Asia, and Africa was common and widespread - but after that, it became much more restricted (and periodic - every 50,00 or 100,00 years) due to climate changes. However, I would not go as far and extend that towards Asia, which IMO only received a couple of inputs: ~250,000 to 200,000 years ago via migrating heidelbergensis, and then again ~100,000 and ~50,000 years ago from modern humans.

    At any rate, the findings are consistent with the view that heidelbergensis and African relatives (or only moderately-Neanderthalized late early humans) were what gave rise to AMHs. This process likely involved Africa, the Near East, and parts of Europe - rather than just Africa - at least over certain time periods.

    I am still very much convinced of OoA if we say a couple of major events ~1.5 million years ago, ~100,000 and ~60,000 years ago, and generalize OoA to include significant gene flow between late European "erectus" (i.e., antecessor and heidelbergensis) and similarly developing Africans, and if we allow for the possibility of additional small admixture events outside of Africa: with Neanderthals (not necessarily required) and heidelbergensis-derivatives (perhaps a bit more likely).

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  4. In the recent paper blogged on by Dienekes earlier this month, Tattersall and Schwartz (http://onlinelibrary.wiley.com/doi/10.1002/ajpa.21443/abstract) re-analyze AMH fossil evidence and seem to conclude that Skhul and Qafzeh specimens tend to lack some important sapient apomorphies (chin, etc.) to classify them as AMH.

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  5. Modern traits come and go in our ancestry. To say that modern looking teeth (and they aren't precisely modern looking) mean modern humans is going too far.

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  6. "However, I would not go as far and extend that towards Asia, which IMO only received a couple of inputs: ~250,000 to 200,000 years ago via migrating heidelbergensis, and then again ~100,000 and ~50,000 years ago from modern humans".

    I agree. SE Asian Homo soloensis seems little changed from the earliest H. erectus in the region, indicating just a small amount of genetic input from outside. On the other hand it is difficult to defend any claim of no genetic input, which some people appear to claim.

    "This process likely involved Africa, the Near East, and parts of Europe - rather than just Africa - at least over certain time periods".

    I agree with that also.

    "seem to conclude that Skhul and Qafzeh specimens tend to lack some important sapient apomorphies (chin, etc.) to classify them as AMH".

    But it's becoming more and more obvious that it is actually impossible to draw a precise defining line between 'archaic' humans and 'modern' humans. As Zacharoo said:

    "many traits that we associate with 'modern' humans were variously interspersed throughout a widespread species of humans"

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  7. "But it's becoming more and more obvious that it is actually impossible to draw a precise defining line between 'archaic' humans and 'modern' humans. As Zacharoo said:

    "many traits that we associate with 'modern' humans were variously interspersed throughout a widespread species of humans"."

    The reality is such that there are no more erectuses, neanderthals, denisovans, etc. Only us, modern humans. And what uniquely characterizes us is modern behavior, namely language, culture, technology, etc. Morphologically we could've evolved anywhere, not necessarily in Africa, but behaviorally we're pretty unique. The diversity of languages (low in Africa and Europe, high in America and Melanesia), one of the key apomorphies of the modern human behavioral species, suggests that we evolved way outside of Africa.

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  8. "The reality is such that there are no more erectuses, neanderthals, denisovans, etc. Only us, modern humans".

    But the evidence is increasingly pointing towards the idea the earlier humans didn't actually die out. They were bred out. Many of us have at least some genes from those species.

    "And what uniquely characterizes us is modern behavior, namely language, culture, technology, etc."

    But like most things that evolve they probably all developed gradually. I can't imagine a whole troop of Homo erectus waking up one morning and discovering that they could all carry on an esoteric conversation about existence.

    "suggests that we evolved way outside of Africa".

    The evidence seems overwhelming that the surviving haplogroups originated, and expanded from, Africa. But haplogroups are only part of the story.

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  9. "But the evidence is increasingly pointing towards the idea the earlier humans didn't actually die out. They were bred out..."

    The admixture is still only a hypothesis. And not the best one, as Cambodians ended up having more Neanderthal admixture than Europeans, which is nonsense. Also, South American Karitiana are the least Denisovans, although Amerindians are said to have originated in Siberia and more specifically in South Siberia. Another absurdity. Culturally, there's no indication that this extinction through interbreeding created some kind of "archaic" cultural forms embedded in some peoples such as Melanesians.

    "But like most things that evolve they probably all developed gradually..."

    Of course. But all extant modern humans (be it San or Karitiana) have essentially the same basic behavioral kit (myths, music, linguistic structures, kinship structures, etc.) which suggests that it emerged prior to the worldwide expansion of modern humans. Genetic genealogies postulating the separation of the San from the rest of humans at 140,000 years, although behavioral modernity is attested worldwide at 45-40K, again make no anthropological sense. As Chapais showed (Primeval Kinship, 2008), humans are different from chimps by having 10-12 unique apomorphies related to kinship, which suggests that they have progressively built up during the course of hominid evolution. But as I show in The Genius of Kinship (2007) Africans have a derived version of this basic human kinship system, which suggests that humans colonized Africa and didn't evolve there.

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  10. (contd.)

    "The evidence seems overwhelming that the surviving haplogroups originated, and expanded from, Africa."

    And the Bible overwhelmingly suggests that the world was created by God in 7 days and that God walked on this Earth like you and me.

    Even if haplogroups built on miniscule samples are real, there are several reasons why existing phylogenies are insufficient evidence for a out of Africa. 1) We don't have any ancient DNA from African AMH and African archaics (although this distinction is too sharp for the messiness of the skull data at hand) to ascertain that Y-DNA A, B and mtDNA L lineages are ancient and originated in Africa. As the extraction of the Mungo man DNA demonstrates, DNA can be obtained from samples in southern latitudes, provided the microenvironment is right. And it showed that populations outside of Africa contain sequences underived from African ones. They just drifted out in the last 50K years. The same ancient DNA studies need to be done in Africa; 2) Y-DNA A, B and mtDNA L lineages aren't found outside of Africa suggesting they are African-specific and hence the result of local evolution from a non-African ancestor. If we originated in Africa, we should be able to find African haplogroups at low frequencies in modern non-African populations and in ancient remains outside of Africa (Kostenki, as you remember is mtDNA U2); 3) non-African lineages are not found in Africa in earlier forms than outside of Africa. E.g., Y-DNA C, D and F lineages are not found in East or North Africa. Same for mtDNA; 4) only derived non-African lineages are attested in Africa (e.g., mtDNA M1, U6, X, N1) suggesting that there was a migration into Africa correlated with the spread of Upper Paleolithic industries into North Africa (Dabban, etc.). There's no archaeological correlate for the (earlier) putative out of Africa migration; 5) the possibility of Y-DNA E originating outside of Africa means that the majority of African chromosomes have a non-African origin; 6) molecular clock has provided widely divergent estimates for the haplogroups and none of them actually matched the finding of the Zhirendong chin at 100K outside of Africa; 7) levels of genetic diversity around the globe are consistent not only with the serial bottleneck model but equally with the relaxation of original selective constraints, with subsequent increase in heterozygosity. The latter trend was experimentally attested (see http://onlinelibrary.wiley.com/doi/10.1002/bies.200900108/abstract). It means that mutation rate may be dependent on population size, which will make the African levels of genetic diversity a derived condition caused by more favorable conditions for the emergence and maintenance of high population size in humans. Previous hominid populations such as Neanderthals were genetically homogeneous, and it's precisely this pattern is attested in modern humans outside of Africa.

    ReplyDelete
  11. "The evidence seems overwhelming that the surviving haplogroups originated, and expanded from, Africa."

    And the Bible overwhelmingly suggests that the world was created by God in 7 days and that God walked on this Earth like you and me.

    Even if haplogroups built on miniscule samples are real, there are several reasons why existing phylogenies are insufficient evidence for a out of Africa. 1) We don't have any ancient DNA from African AMH and African archaics (although this distinction is too sharp for the messiness of the skull data at hand) to ascertain that Y-DNA A, B and mtDNA L lineages are ancient and originated in Africa. As the extraction of the Mungo man DNA demonstrates, DNA can be obtained from samples in southern latitudes, provided the microenvironment is right. And it showed that populations outside of Africa contain sequences underived from African ones. They just drifted out in the last 50K years. The same ancient DNA studies need to be done in Africa; 2) Y-DNA A, B and mtDNA L lineages aren't found outside of Africa suggesting they are African-specific and hence the result of local evolution from a non-African ancestor. If we originated in Africa, we should be able to find African haplogroups at low frequencies in modern non-African populations and in ancient remains outside of Africa (Kostenki, as you remember is mtDNA U2); 3) non-African lineages are not found in Africa in earlier forms than outside of Africa. E.g., Y-DNA C, D and F lineages are not found in East or North Africa. Same for mtDNA; 4) only derived non-African lineages are attested in Africa (e.g., mtDNA M1, U6, X, N1) suggesting that there was a migration into Africa correlated with the spread of Upper Paleolithic industries into North Africa (Dabban, etc.). There's no archaeological correlate for the (earlier) putative out of Africa migration; 5) the possibility of Y-DNA E originating outside of Africa means that the majority of African chromosomes have a non-African origin; 6) molecular clock has provided widely divergent estimates for the haplogroups and none of them actually matched the finding of the Zhirendong chin at 100K outside of Africa; 7) levels of genetic diversity around the globe are consistent not only with the serial bottleneck model but equally with the relaxation of original selective constraints, with subsequent increase in heterozygosity. The latter trend was experimentally attested (see http://onlinelibrary.wiley.com/doi/10.1002/bies.200900108/abstract). It means that mutation rate may be dependent on population size, which will make the African levels of genetic diversity a derived condition caused by more favorable conditions for the emergence and maintenance of high population size in humans. Previous hominid populations such as Neanderthals were genetically homogeneous, and it's precisely this pattern is attested in modern humans outside of Africa.

    ReplyDelete

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