Neanderthals

"This sentence is language but not speech." Simply reading it makes it true.Say it aloud and it becomes a lie.H. erectus may have had the rudiments of language, but may have been unable to communicate via speech as we know it.At any rate, Neanderthals may not have disappeared if you understand the Multi-Regional Hypothesis.------------------
Bringer of fire, trickster, teacher.

Our species may be older than a million years. This is the crux of the multiregional hypothesis.You do realize that you can have language without speech and American Sign Language is an example of this.The replacement hypothesis many of us believe does not account for regional differences that we see in modern humans. These differences have been found in erectus fossils going back about a million years. There is also evidence that modern form occured in regions before the African mtDNA arrived.Check the links: Just a moment...Just a moment...Abstract from second link:Human mtDNA shows striking regional variation, traditionally attributed to genetic drift. However, it is not easy to account for the fact that only two mtDNA lineages (M and N) left Africa to colonize Eurasia and that lineages A, C, D, and G show a 5-fold enrichment from central Asia to Siberia. As an alternative to drift, natural selection might have enriched for certain mtDNA lineages as people migrated north into colder climates. To test this hypothesis we analyzed 104 complete mtDNA sequences from all global regions and lineages. African mtDNA variation did not significantly deviate from the standard neutral model, but European, Asian, and Siberian plus Native American variations did. Analysis of amino acid substitution mutations (nonsynonymous, Ka) versus neutral mutations (synonymous, Ks) (ka/ks) for all 13 mtDNA protein-coding genes revealed that the ATP6 gene had the highest amino acid sequence variation of any human mtDNA gene, even though ATP6 is one of the more conserved mtDNA proteins. Comparison of the ka/ks ratios for each mtDNA gene from the tropical, temperate, and arctic zones revealed that ATP6 was highly variable in the mtDNAs from the arctic zone, cytochrome b was particularly variable in the temperate zone, and cytochrome oxidase I was notably more variable in the tropics. Moreover, multiple amino acid changes found in ATP6, cytochrome b, and cytochrome oxidase I appeared to be functionally significant. From these analyses we conclude that selection may have played a role in shaping human regional mtDNA variation and that one of the selective influences was climate.The Eve hypothesis postulates that mtDNA was simply carried along with a migrating population. While the MRH states that genes were exchanged and natural selection facilitated the spread of favorable traits found in mtDNA.Then you also have to consider that Neanderthals are only really different from other erectus in that Neaderthals have greater cranial capacity. There does not appear to be any evidence that they were any more intelligent than other erectus, their technology was similar to other erectus. Then you also have a reduction in cranial capacity with sapiens and an increase in technology. The reliability of using cranial capacity to mark a species boundry is a dubious one.------------------
Bringer of fire, trickster, teacher.

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The multiregional hypothesis does not put our species at several million years old. With multiregionalism, one line changes from an ancestral species to modern H. sapiens. With replacement, one branch outcompetes another. Either way, H. sapiens shows up at about the same time. That part doesn't change. What changes is how we evolved, not when.

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The division of a species across time is based on morphology, I tend to lump erectus with sapiens and the genus Homo with Pan. There is good genetic reason to not split Pan and Homo other than an inate chauvenism on our part. I believe the same holds true for chronological/morphological divisions. We really have not changed that much physically in a million years.Multiregionalism states that humans evolved in situ in each of the 4 regions of the Earth with structural features being retained by modern humans in each region. Genes from one region were exchanged for genes from another with regional variation being retained.A Neanderthal skull is the same with ergaster/erectus skulls in that all have the same morphology at the base. The occipital plate of the skull is flattened where the spinal cord enters and small mastoid processes occupying the same horizontal plane as the occipital condyles. In sapiens, the base of the skull has a rounded shape and the masoid processes are elongated to maintain the position with the condyles and preserve the mechanical leverage of the neck muscles on the base of the skull. It is this structural change that matters for sapienization, not cranial capacity.The recent mtDNA studies fit more closely with the MRH than the popular Eve theory.------------------
Bringer of fire, trickster, teacher.[This message has been edited by Speel-yi, 10-05-2003]

Alrighty then, battling links from Nature Nature - Not FoundQuote from abstract:"Africans have had a huge genetic impact on humanity," he says. "But my analysis really isn't compatible with complete replacement."Can't post more now...must...watch...stupid...baseball game.

mt DNA is handy because it doesn't recombine during meiosis like chromosomal DNA does, it is also passed only through the female parent to the offspring. Y chromosome DNA also is largely not subject to recombination, so it can be handy as well.What we see in present day populations is a retention of physical features in humans that have been seen in ancient erectus populations.http://www-personal.une.edu.au/~pbrown3/dali.htmlFrom the site:

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Wu (1981, 1989) found that most of the cranial dimensions and morphological features of Dali were intermediate between Homo erectus and H. sapiens, with Dali assigned to archaic H. sapiens. Craniofacial anatomy and vault shape are distinct from European Neandertals and earlier European hominids like Petralona and Atapeurca.

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What we see is distinct and intermediate forms of hominids that retain features found in modern populations in these geographic areas. Two key words--intermediate and distinct.What the Out of Africa model proposes is that an isolated population of hominids evolved into modern H. sapiens and then migrated out of Africa to replace the more primative hominids found in those areas. This is an allopatric speciation model and it employs competitive or Gaussian exclusion to explain the sudden disappearance of the erectus types that coincide with the appearance of H. sapiens. Gaussian exclusion only works with 2 separate species that are unable to interbreed and compete for the same niche. It does not work with the same species, if genes are exchanged, then the Out of Africa model falls apart and MRH is the best explanation.mtDNA can be spread by either migration or gene exchange, it is inconclusive as a means by itself to determine modern origins.Further, two of the tenets of Darwinism are that 1) populations will have varied traits and 2) that a trait can be selected for by natural selection. Given this, it can be seen that H. erectus could have forms within a population that deviated from the norm enough to be recognized as H. sapiens by modern observers. For an adherant of Regional Continuity, it would not be too surprising to see a specimen dated 160,000 years ago that appeared to be modern since it would still represent a member of an H. erectus that varied from the norm. We could expect to see some forms become more common with reduced selection and possibly become the norm with directional selection.------------------
Bringer of fire, trickster, teacher.[This message has been edited by Speel-yi, 10-06-2003]

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Yes, but the paper you quoted was about mtDNA haplotypes that arose outside Africa and then increased in some places outside Africa due to selection. You were citing it as if it were evidence that selection had caused the spread of African mtDNA to replace non-African, which it isn't.

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It has been traditionally viewed that any mtDNA did not have any selective advantage, it was only a passenger carried along by autosomal genetics.

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You also claimed that selection was inconsistent with an Out of Africa model, which isn't true.

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Where did I claim this?My claim is simple: That erectus and sapiens were fully capable of interbreeding, they did not form two separate species in a biological sense.------------------
Bringer of fire, trickster, teacher.

Mammuthus said:

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My overall point is that one should take the claims made by the ancient DNA community and the human evolution community in general with a grain of salt. They argue as badly as creationists sometimes.

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True, there's a lot of assumptions being made. I find it particularly annoying that some evidence is presented as "proof". The sampling sizes are hmmmm...kinda tiny for some of the conclusions we see. The skeletal remains are interesting, but for a trait to disappear and then reappear really throws a wrench into some of the conclusions about Out of Africa.sfs said:

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What do you mean by "traditionally"? Many analyses have considered the possibility of selection in recent mtDNA and Y evolution. Look at the big Takahata paper on testing multiregionality, or Kaessmann et al's 1999 paper on Xq13.3, or Stumpf and Goldstein's review article on the Y. It has been widely recognized that selection is a possibility that needs to be taken into account when drawing conclusions from any locus (Takahata even modeled it), and especially for mtDNA and the Y, since they're nonrecombining and single-copy.

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The Wilson group in its original study allowed for a population of 20,000 in the group which mitochondrial Eve lived with. This was based on a purely stochastic model and did not include the possibility that selection was involved in mitochodrial genetics. Selection by and large was thought of on the autosomal level.------------------
Bringer of fire, trickster, teacher.[This message has been edited by Speel-yi, 10-08-2003]

I think a lot of this stems from the backlash against the old Out of Europe hypothesis that had people rejecting some of Darts early finds in Africa.I also see this type of behavior with archeological finds in America. Not 40 miles from where I sit, there's a mammoth kill site that shows some pretty decent evidence of human occupation. The only problem is that the first radio-carbon dating came back with a date of 19,000 BP, it was then rejected as an archeological site because anything older than 12,000 BP can't have shown signs of human occupation since everyone knows that humans were not here until 12,000 BP. Another persistant notion is the idea of replacement of old populations with new ones of the same species. The idea that humans exterminate each other is a tough one to eliminate from modern scientists minds. We see the same thing with the Spirit Cave Man and Kennewick Man since they appear to be different from modern Indians and obviously were wiped out by them.------------------
Bringer of fire, trickster, teacher.

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I still don't quite get it. What about the divergent DNA? Isn't it different enough to both not come from contamination and to separate us from the neanderthals?
Or is that whole samples are rejected and there is the possibility of some heanderthals not being all tha divergent?

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The contaminated DNA would be modern and since older DNA that looked like modern DNA it is assumed to be the contaminated sample. I think you sum it up in your second statement if I read it right.Not really sure if will help, but try this link:http://www.actionbioscience.org/evolution/johanson.htmlIt also might help if you think about what a species is in the first place. A dachshund and a great dane may be the same species, but the chances of offspring are slight unless they get a little help. However, the first thing two populations of a species will do when they come into contact is exchange genes if at all possible. I see no reason why anyone would expect older forms of Homo to be unable to interbreed with newer forms.One other thing is that you would expect Africa to have larger populations of hominids than any of the other regions due to its favorable climate and thus contribute more to the genetics of modern humans in that way.Try the link and see if that helps.------------------
Bringer of fire, trickster, teacher.[This message has been edited by Speel-yi, 10-12-2003]

The problem with the Monte Verde site is that is was so poorly done, they did not use good methods at all. There was enough evidence there that it did look good to a fair number of experts, so it is generally accepted as having a legitimate date. Not much else will come from it I think because it is so poorly done. There are a few die hards that don't accept it.The problem is that we won't see many older sites until funding allows for the possibility that humans lived in the Americas before 12 KYA. Any site having old C-14 dates is excluded. What kind of science is that? I have to think that careerism is coming in before good science.Martin's pliestocene overkill is not generally accepted here, there's a couple of other hypotheses being kicked around, but my personal favorite involves a theory with human predation altering the environment enough to cause heavily k-selected species like mammoths to be outcompeted by smaller, faster reproducing species.Interesting stuff about Paabo and Cooper, I'd love to see some challenges to their methods because a lot of people are taking conclusions at face value. I think it also ignores some morphological evidence.Check the next link out, as it has some interesting points to ponder:http://cogweb.ucla.edu/ep/Neanderthal.html------------------
Bringer of fire, trickster, teacher.

sfs stated:

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Whether it was a complete replacement or not is not clear, but it seems to be have been pretty thorough-going.

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There's the sum of it, the more people take an honest, objective look at all of the evidence, the more Out of Africa looks like MRH. It doesn't matter how big the populations were, since they remained viable for hundreds of thousands of years in their respective regions.Migration did occur and the resultant hybrids were able to select the most suitable genes for each region. The end result is that each hybrid was better suited to each environment than either of the parent populations.------------------
Bringer of fire, trickster, teacher.

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Of course it matters how big the ancestral populations of non-Africans were: if they were really small, then they weren't the archaic non-African populations that were in place, since they had to be larger.

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Why would they have to be larger? Larger than the Africans or larger than the regional populations? How can it be if they were really small, that they were then the archaic non-Africans?What I'm saying is that the populations may have been small, but that they were able to migrate, exchange genetic information and continue to exist for a long time well before the African genetic migration.

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To clarify my previous statement: at present, the evidence from human genetics, taken as a whole, indicates a complete replacement of non-African archaic populations by African ones. It is possible that some admixture did occur and the evidence has either been lost or lies in loci that haven't been examined yet, but at this point there is no such evidence.

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Part of the problem is that mtDNA is only transmitted through the mothers line. I know it doesn't mean much, but if you look at mtDNA closely enough, you could see that a paternal grandmother would not be related to her grandson and that if a woman produced no sons, then her mtDNA line will disappear. If a woman produces more daughters, then her mtDNA is disprortionately represented in the next generation.We also assume that the mitochondrial Eve was not the only woman of her generation, but that she had 10,000 women in her cohort. So we apply a rule that tells us about the other women of her day, but then somehow expect the rules to behave differently a hundred millenia later when people migrate out of Africa.------------------
Bringer of fire, trickster, teacher.

You don't have to think Indians were ecologists, just that they would switch prey species when one type became scarce and another was more abundant. There were plenty of bison to hunt while the megafauna died out. There are a number of sites also with dead mammoths and no sign of human agency. Finding an actual kill site is a really big deal and hard to come by.There were also some other fauna that became extinct and did not have any value as a food source like the short faced skunk, Brachyprotoma obtusata somehow I can't see those things being hunted in preference to things like deer.------------------
Bringer of fire, trickster, teacher.

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MRH requires that every one of the populations was very small, and at the same time that there was a high enough density across the entire range to maintain substantial gene flow. That just doesn't seem possible.

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It would mean having an effective breeding population of around 10,000 spread over two continents. This would not be that big of a stretch at all. First we would have high inbreeding and this would not be surprising since most small scale societies still participate in marriages between cousins by preference.University of Manitoba - University of Manitoba - Contact Information

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The widespread presence of cross cousin marriage in its varous forms has been of special importance to the structuralist anthropologist, Claude Levi-Strauss, and to his formulation of alliance theory (Levi-Strauss 1969). He views marriage as a form of exchange that simultaneously expresses differences between groups and unites them into coherent social systems. His observations focus on the significance of the three alternative marriage rules for the emergence of different social dynamics.

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Humans have not been panmictic for a long time and it's only been recently that the incest taboo has been applied to cousins. I would expect inbreeding to be very much part of the genetic background for ancient humans. In small scale societies, the genetic relatedness of full sibs should be somewhat greater than the 0.5 we would see in a large, random mating population.The incest taboo would still come into play as humans seem to prefer mates that they were not reared with, young people would go to great lengths to find an exogamous mate. (A long trek for some good sex is not too hard to imagine now is it?)We see an example of the incest taboo being naturally applied between non-related individuals that were reared together in the modern Kibbutz.http://www.ed.ac.uk/ces/tiy/tiy98papers/DAR_Y.html

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We find that a quarter of the subjects from the senior cohorts, women and men respectively, were married by the ages of 19 and 21, and in the junior cohorts by 21 and 23. Half the subjects in the first group were married at 21 and 23, and in the second by 24 and 25. A 75% marriage rate is reached in the first group at 23 and 25, and in the second group only at 27 and 29.

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There seems to be an inhibition to mating between individuals of cohorts reared together and the preference is for mating outside of a community. Traveling for a mate is not too much of a stretch.(Evolutionary psychologists cite the Kibbutz as an example of an inborn incest taboo.)So we would see populations from demes with effective breeding populations of around 500 and then periodic mating between demes from adventurous youths traveling fairly great distances to find a suitable mate.One other thing is that in modern Africa we see at least 3 distinct racial types, while outside Africa we see the bulk of the populations are made up of only 2 racial types.------------------
Bringer of fire, trickster, teacher.[This message has been edited by Speel-yi, 10-14-2003]

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If left in a fairly stable environment for long enough, most species tend toward equilibrium.

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This is only for K-selected species, r-selected species will go through boom and bust cycles and some of these appear to have gone extinct as well. It's really tough to overhunt r-selected species and they seem to do better when they are prevented from the boom and bust cycles.A single mammoth would feed a few people for a long time, so you kill one or two a year per group at maximum. They probably would have greater mortality from non-hunting causes anyway. Plus, who's to say that Paleoindians didn't just wait for a non-reproductive adult mammoth to leave the herd because they couldn't keep up and then make a kill on a solitary adult that wasn't in its prime? All the Indians would have done would be to speed up the inevitable.------------------
Bringer of fire, trickster, teacher.[This message has been edited by Speel-yi, 10-14-2003]