Neanderthals at the end of their days

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What was Neanderthal-Modern Human interaction really like?
Fifty four teeth (some of which are fragments) and nine other bones dating to about 40-43,000 years ago represent the “most recent, and largest, sample of southern Iberian late Neanderthals currently known.”

These and some closely related remains may indicate that these Middle Paleolithic holdouts were kissing cousins of nearby anatomically modern humans. Or maybe not.

We know that Neanderthals occupied all of Europe for over 125 thousand years during a period known (from the artifacts) as the “Middle Paleolithic.” During this time, modern humans had become well established (and were using a similar suite of artifacts known as “Middle Stone Age” technology) in Africa. Prior to 40,000 years ago modern humans … most by now possessing a distinctly different suit of artifacts … began to displace or replace the Neanderthals across Europe. Despite the fact that you will hear people argue over what this displacement or replacement event consisted of, it is most likely that over several thousands of years these small scattered groups of hunter gatherers interacted in a number of ways, and that this period in our history was fairly complex.

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It is quite likely that many patches of Europe were simply disoccupied by Neanderthals for some reason or another … as one might expect during peirods of changing climate with a thinly scattered and highly mobile population … and when people came back to those particular valleys or subregions, it happened to be the moderns and not the Neanderthals. There may have been competitive, even bellicose interactions here and there, though there is not one shred of evidence to suggest this. Not a single Neanderthal has been found with a modern human hunting implement stuck in it’s skull, or visa versa. The demise of the Neanderthal was not a matter of Mr. Modern in the Dordogne with the Side Scraper.

The fact that we are what we refer to as “modern humans” and it is we, not the Neanderthals who ended up occupying Europe and West Asia causes most modern humans to assume that they (the Neanderthals) were doin’ it wrong, or that the modern humans had some special advantage over the Neanderthals. Could be. But it is also true that VHS beat Betamax, and most people use Windows and not Apple or Linux computers.

The story of this replacement is largely known through the artifacts, which are relatively common across Europe. This story shows a generally east to west movement of moderns, but with considerable spatial complexity, and with the modern human technology replacing the Neanderthal last in southern Iberia. During this time there is evidence of a sort of mixing of the technologies, indicating that there were long term and meaningful interactions between at least some groups of modern humans and Neanderthals.

The DNA evidence, both of modern populations and of ancient groups (including DNA from several Neanderthal bones) seems to indicate that there is no significant (or even insignificant,really) contribution of DNA to living human populations. However, this does not rule out interbreeding in these early days. The truth is that the modern humans that occupied Europe right after the replacement (e.g., 30,000 years ago) may have also contributed relatively little to modern European populations. There is probably more Central Asian blood in central Europe than Cro-Magnon blood. Like it or not, if you are European, Genghis Kahn is more likely to be your uncle than, say, King Arthur.

So this leaves thebones. The physical remains … the skeletal bits and pieces … mostly tell a story of distinct differences between modern humans coming from Africa and Neanderthals, but that is because most of the skeletons are not from the time period of likely interaction between groups in Europe. In the Middle East, where both types of human seemed to take turns occupying certain landscapes over several tens of thousands of years, there is not clear evidence of intermixing of the groups. But in the late European Neanderthal populations, there may be some evidence of the relationship between the groups getting … well, let’s just say it’s complicated.

The Iberian bone and tooth fragments mentioned above are linked to a larger sample that for the purposes of analysis have been grouped together to assess the possible relationships of these late Neanderthals and the anatomically modern humans that were contemporary with them. These remains are the subject of study in a paper just now coming out in the Proceedings of the National Academy of Sciences. The paper by Walker, Tibert, Lopez, Lombardi, Perez-Perez, Sapata, Ortega, Higham, Pike, Schwenninger, Zilhao and Mr. Neanderthal himself, Trinkaus is titled “Late Neandertals in Southeastern Iberia: Sima de las Palomas del Cabezo Gordo, Murcia, Spain” and concludes (from the abstract) the following:

Middle Paleolithic fossil human remains from the Sima de las Palomas in southeastern Iberia (dated to ≤43,000-40,000 calendar years before present) present a suite of derived Neandertal and/or retained ancestral morphological features in the mandibular symphysis, mandibular ramus, dental occlusal morphology, and distal hand phalanx. These traits are combined with variation in the mandibular corpus, discrete dental morphology, tooth root lengths, and anterior dental size that indicate a frequency difference with earlier Iberian and more northern European Neandertals. The Palomas Neandertals therefore confirm the late presence of Neandertals associated with the Iberian persistence of the Middle Paleolithic, but suggest microevolutionary processes and/or population contact with contemporaneous modern humans to the north.

What does it all mean? Well, the study is a bit technical, but in essence, measurements of these bits and pieces, in comparison with matched measurements from different samples of clear Neanderthals and modern humans, strongly indicates that these late-dated bones are indeed Neanderthals. But they differ in ways that might indicate genetic mixing with modern humans living to the north. Or, the variations in measurements might indicate local, in situ evolution in a relatively isolated population.

ResearchBlogging.orgWill we ever be able to make a more definite statement than this? Yes, if more remains are found. It will never be able to say for certain exactly who was sleeping with whom and where and when (this is hard enough to do when all the actors in the drama are alive and kicking!) but with more physical, bony remains from this region it would be easier to suggest plausible scenarios for the last centuries of the existence on this earth of the Neanderthals.

Michael J. Walker, Josep Gibert, Mariano V. Lopez, A. Vincent Lombardi, Alejandro Perez-Perez, Josefina Zapata ́ ́ ́, Jon Ortega, Thomas Higham, Alistair Pike, Jean-Luc Schwenninger, Joao Zilhao, Erik Trinkaus, ̃ ̃ (2008). Late Neandertals in Southeastern Iberia: Sima de las Palomas del Cabezo Gordo, Murcia, Spain
Proceedings of the National Academy of Sciences

Comments

  1. #1 ringo
    December 13, 2008

    I wonder if anyone has done the basic geometry to determine if a Neanderthal female or a modern female could physically give birth to a mixed child.

    If only male-Neanderthal/female-human pairs could produce offspring (or, even more, if female-Neanderthal/male-human pairings often resulted in the death of the female), then any analysis based on mitochondrial DNA is useless, and game theory tells us that any significant amount of mixing will eventually result in Neanderthal extinction.

  2. #2 ringo
    December 13, 2008

    I wonder if anyone has done the basic geometry to determine if a Neanderthal female or a modern female could physically give birth to a mixed child.

    If only male-Neanderthal/female-human pairs could produce offspring (or, even more, if female-Neanderthal/male-human pairings often resulted in the death of the female), then any analysis based on mitochondrial DNA is useless, and game theory tells us that any significant amount of mixing will eventually result in Neanderthal extinction (while leaving behind some “Neanderthal” fossils with modern human traits).

  3. #3 Greg Laden
    December 13, 2008

    It has been looked at and it is probably not a factor.

    Right now I’m blanking on the name of the woman who wrote her thesis on this … but it was pretty clear that this neanderthal/modern human difference in birth spacing and gestation length is not real. It would not matter, most likely.

  4. #4 ringo
    December 13, 2008

    Ah, but I’m not talking about birth spacing and gestation length. I’m talking about a neanderthal head fitting through a human pelvis.

    We have all sorts of adaptions to make labor and delivery possible (open skull sutures in infants, non-optimal pelvic tilt in women, etc.). What if a half-modern infant routinely got stuck in a Neanderthal birth canal, but survived if born to a modern human?

  5. #5 Greg Laden
    December 13, 2008

    You are talking about both. Any pre-natal human will fit through a birth canal if it is born early enough, so gestation length can be important.

    Neanderthal heads are not smaller than human heads. The adaptations you are quite correctly pointing out are likely operative in both species. There shouldn’t be a problme.

  6. #6 Anne Gilbert
    December 13, 2008

    Dr. Laden and Ringo:

    I think the name of the woman in question was Karen Rosenberg(I had to do some thinking to bring up the name). She did some rt of study of Neandertal pelvises, and determined that N’s had the same gestation period as “modern’ humans, rather than proposed 12-month pregnancies. And yeah, Neander heads were (somewhat), and perhaps — a very big perhaps, IMO — this might have been a problem, especially if there was a significant difference in size between Neandertals and ‘moderns”. But I’ve also read —somewhere — that while it’s easy to tell a “modern” human from a Neandertal, it’s also true that, apparently, there wasn’t that much difference in size between N’s and early AMH. And there are also indications, from the study of certain fossils — ndija is the only one I can think of at the moment — that some later Neandertals seemed to be becoming more “gracile”, whether through admixture with whatever modern populations were around at the time, or from other processes.
    Anne G

  7. #7 ringo
    December 13, 2008

    Actually, Greg, your clarification on gestation length brings up another possibility. What if Neanderthal women were, in fact, able to birth a half-modern child, but those children were born at a much earlier level of maturity than full neanderthals? One of our large-brain adaptions is early-born infants, and a social system that will care for them while they finish developing. (The birth trigger is lung development, not head size, but I’m not sure how this would interact with maternal physiology).

    On a tangential note, British national health has just had to change their prenatal exam charts to take new immigrants into account (smaller fetal size is not necessary pathology – you’ve got to take mum’s ethnicity into account). So perhaps we’re not done with this particular evolutionary pressure.

  8. #8 ringo
    December 13, 2008

    Just found a reference I was looking for:

    http://www.ncbi.nlm.nih.gov/pubmed/1754497
    (Gestational duration and birthweight in white, black and mixed-race babies.)

    Likely that size at birth is a combination of DNA and SES, but the outcome in life will be pure SES. Back to game theory.

  9. #9 tresmal
    December 13, 2008

    Has anyone looked into the possibility that Neanderthal/Modern Human hybrids might have been sterile, like mules?

  10. #10 Greg Laden
    December 13, 2008

    Ann: Yes, that is who it was, excellent memory!

    Ringo: We are definitely not done with this particular evolutionary story, I’m sure. But, I do think the size differences are negligible.

    The idea of modern humans and Neanderthals producing sterile but vigorous hybrids, like mules, was explored by Bjorn Kurten in his book Dance of the Tiger, a novel.

  11. #11 brooks
    December 13, 2008

    tresmal:

    i’m not expert, but to the best of my knowledge, neandertals had 2n=46 just like us. (can anyone tell me when the switch from 2n=48? i’m assuming somewhere well past the LCA with chimps. maybe it’s what finally, permanently split the gene-pool?) if human/neandertal hybrid offspring had fertility problems, it shouldn’t be because of mismatched chromosomes.

  12. #12 Greg Laden
    December 13, 2008

    Brooks: There is evidence that the chimp/human shift in chromosome number is very recent in human history, recent enough that Neanderthals could be different. There is a research team working on this right now but I am not a liberty to say anything more. Other than since I have not heard anything in a while it probably did not work out…..

  13. #13 brooks
    December 13, 2008

    GL:

    very cool! that’s what one gets for assuming, heh. had no idea that that fusion was so recent. that would almost certainly preclude any significant mixing, then.

    chromosome number 2 is here… pretty damn cool– cross a couple of arms together, something sticks, and we have 23 pairs instead of 24!

  14. #14 Stacy S.
    December 13, 2008

    @ Brooks – Jeremy Mohn from Stand up 4 real science has done an excellent video about the 24 to 23 switch.
    http://www.teachertube.com/view_video.php?viewkey=2776ab9d15abf7ef6f38

  15. #15 brooks
    December 14, 2008

    Stacy S.:

    tyvm, i’ll definitely take a look.

  16. #16 Greg Laden
    December 14, 2008

    Stacy: Thanks, I made a post with this video and the next two in the series (from the Youtube source), which will be up tomorrow AM.

  17. #17 shecky
    December 14, 2008

    Geee, when I saw the title of your post I assumed it was going to be a blurb on the end of the Bush Administration ;-)

  18. #18 Bruce Molholt
    December 16, 2008

    Nah, Greg. Neanderthals never became extinct, only morphing into Illinois politicians. We still have Rod Blagojevich.

  19. #19 Fred Keire
    December 16, 2008

    Has anyone addressed the possibility that Neanderthalers may have been considered “bush meat” by modern humans? Any evidence such as on bone fragments on bone marrow extraction?

  20. #20 Greg Laden
    December 16, 2008

    Fred: The evidence for Neanderthals being eaten and/or their bones being treated as food or otherwise messed with by using stone tools on them is abundant. However, this evidence does not specifically date to the period or place of modern human overlap with neanderthals. Neanderthals may have been either eating each other or at least playing around with the bones a lot. The original Neanderthal skull cap (the most famous Neanderthal bone) was treated with stone tools .. there are cutmarks .. and used as a bowl for a long period of time.

    Of course, modern humans also, at various times and places, done a lot of cutting up and in some cases almost certainly eating of each other.

  21. #21 Matthew
    December 16, 2008

    Any idea how Svante Pääbo is doing with his reconstruction of the Neanderthal genome? That might answer a lot. The only question is which modern human woman will volunteer to birth a new Neanderthal?

  22. #22 Greg Laden
    December 16, 2008

    I just saw Svante speaking about this a few weeks ago. They are doing quite well. The statement I made above about DNA includes what I learned form him in October.

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