mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== ANTHROPOLOGY: ON THE NEANDERTHALS The following points are made by Pat Shipman (American Scientist 2004 92:506): 1) Neandertals (Neanderthals) were probably not members of our own species, judging from recent analyses of mitochondrial DNA. Nonetheless, Neandertals were clearly built on a human-like plan (or vice versa) with some crucial modifications. A glance at the fossil remains of these hominids shows that Neandertal bones are much more robust than those of modern Homo sapiens. The skulls of the two species also show several striking differences. One of the most noticeable Neandertal features is the unmistakably large, bony browridges that stick out over the eyes. Below the orbits, the face is more prognathic -- the nose and jaw protrude farther in front of the braincase -- than a human face. The prominent nasal bones in Neandertal skulls top wide nasal openings, suggesting that they sported large, aquiline noses. Unlike the smoother, rounded contour of the human skull, the back of the Neandertal skull has a distinctive bulge, often referred to as a chignon or bun. Overall, the Neandertal skull resembles what you might expect if someone took a human skull made of rubber, grabbed it by the face and back of the head, and pulled. 2) These comparisons have attracted the attention of researchers who study the interactions between evolution and development from birth to adulthood -- so-called "evo-devo." Put simply, they wanted to know: How do you grow up Neandertal? In the spring of 2004, several studies offered answers to this question. F. Ramirez Rozzi and J.M. Bermudez de Castro (1) compared the rates of dental growth in several species within the genus Homo, including Neandertals. They examined the perikymata -- small enamel ridges on the tooth surface -- of incisor and canine teeth from 55 Neandertals, 25 Homo antecessor and Homo heidelbergensis individuals (two species that some anthropologists group together) and 39 ancient but anatomically modern humans. 3) Perikymata are created as a tooth grows. In humans and their close kin (such as Homo erectus), one ridge is created approximately every nine days during tooth development. The ridges of more distant relatives, including chimpanzees and gorillas, are formed at shorter intervals. By counting the number of perikymata, investigators can calculate how long the tooth took to form. Ramirez Rozzi and Bermudez de Castro (1) found that Neandertals formed their teeth in fewer days than did H. antecessor and H. heidelbergensis. If Neandertals had been the most ancient of the lot, one might expect them to be the most ape-like. But although the other fossil species are older still, they already show the human pattern. The finding is also a surprise because some researchers still propose that Neandertals are basically just strange-looking humans -- a judgment challenged by this fundamental difference. 4) Dental maturity is a common proxy for overall maturity because neurological, skeletal and sexual milestones are correlated with the pace of tooth mineralization. Ramirez Rozzi and Bermudez de Castro (1) concluded that faster dental development meant that Neandertals reached adulthood 15 percent sooner than humans, on average. To state this finding in practical terms, if humans attain physical maturity at 18 years, Neandertals were similarly grown at 15 years. The study also examined the spacing of perikymata across the front surfaces of incisors and canines. Dental enamel forms first at the tip of the crown -- the first point to emerge from the gum -- and then proceeds toward the roots. 5) In modern humans, the perikymata are widely spaced in the half of the tooth that formed first, indicating that lots of enamel was deposited during each nine-day increment. On the second half of each human tooth, the ridges are more closely spaced, showing a slower daily rate of enamel formation. Like human teeth, Neandertal teeth look as if they grew rapidly at first and then slowed down. However, on the part of each Neandertal tooth that grew later, the perikymata are more spread out than in their human counterparts. In other words, although the rate of enamel formation also decreased with age in Neandertals, the slowdown was less pronounced. This pattern of dental growth resembles that of apes. We know that the apes of today reach physical maturity much faster than humans. So, presumably, did Neandertals.(2-4) References (abridged): 1. Krovitz, G. 2003. Shape and growth differences between Neandertals and modern humans: Grounds for species-level distinction? In Patterns of Growth and Development in the Genus Homo, ed. J. L. Thompson, G. E. Krovitz and A. J. Nelson. Cambridge, UK: Cambridge University Press 2. Ramirez Rozzi, F., and J. M. Bermudez de Castro. 2004. Surprisingly rapid growth in Neanderthals. Nature 428:936-939 3. Trinkaus, E. 1995. Neandertal mortality patterns. Journal of Archaeological Science 22:121-142 4. Williams, F. L., L. R. Godfrey and M. R. Sutherland. 2003. Diagnosing heterochronic perturbations in the craniofacial evolution of Homo (Neandertals and modern humans) and Pan (P. troglodytes and P. paniscus). In Patterns of Growth and Development in the Genus Homo, ed. J. L. Thompson, G. E. Krovitz and A. J. Nelson. Cambridge, UK: Cambridge University Press American Scientist http://www.americanscientist.org -------------------------------- Related Material: ANTHROPOLOGY: ON NEANDERTHAL MITOCHONDRIAL DNA The following points are made by Alan Cooper et al (Current Biology 2004 14:R431): 1) The genetic affinities of the earliest modern humans of Europe and the earlier hominid occupants of the area, the Neandertals, has remained a hotly debated topic since the discovery of the extraordinarily robust skull cap and limb bones in the Neander Valley in 1856. While it is impossible to rule out a surreptitious coupling of the two groups in the more than 10,000 years they apparently co-occupied Europe, recent research and population genetic theory suggest that any genetic interchange was limited. 2) This issue is central to the two main theories of modern human origins: the replacement model, where modern humans rapidly replaced archaic forms, such as Neandertals, as they began to spread from Africa through Eurasia and the rest of the world sometime around 100,000 years ago [1]; and the multi-regional model, where genetic exchange or even continuity exists between archaic and modern humans [2,3]. Two years ago, a review [4] reported that characteristic mitochondrial DNA (mtDNA) sequences retrieved from remains of four Neandertals are absent from modern human populations. It remained possible, however, that these sequences had been present in early modern humans, but had been lost through genetic drift or the continuous influx of modern human DNA in the intervening 28,000 years since Neandertals became extinct. 3) The difficulty in testing these ideas using ancient DNA is that most ancient human remains are contaminated with modern human DNA, which deeply penetrates bone and teeth samples during the washing and routine handling that takes place after excavation. This modern DNA will either out-compete authentic ancient sequences in PCR reactions, or recombine with them to produce artificial, but authentic looking genetic sequences [5]. Consequently, even when strict criteria for authenticating ancient DNA results are followed, it can be impossible to determine the authenticity of results. 4) The approach taken recently by Serre et al [2004] avoided this problem by searching only for the presence of Neandertal mtDNA sequences in both early modern human and Neandertal fossils, while ignoring modern human sequences because they are potentially contaminants. Four additional Neandertal specimens tested positive, but Neandertal sequences could not be detected in five early modern human fossils with biochemical preservation consistent with DNA survival from the Czech Republic and France. This appears to confirm that sequences characteristic to Neandertal remains were not widespread in early modern humans. 5) In summary: Mitochondrial DNA sequences recovered from eight Neandertal specimens cannot be detected in either early fossil Europeans or in modern populations. This indicates that if Neandertals made any genetic contribution at all to modern humans, it must have been limited, though the extent of the contribution cannot be resolved at present. References (abridged): 1. Stringer, C.B. and Andrews, P. (1998). Genetic and fossil evidence for the origin of modern humans. Science 239, 1263-1268 2. Hawks, J.D. and Wolpoff, M.H. (2001). The accretion model of Neandertal evolution. Evol. Int. J. Org. Evol. 55, 1474-1485 3. Templeton, A. (2002). Out of Africa again and again. Nature 416, 45-51 4. Schmitz, R.W., Serre, D., Bonani, G., Feine, S., Hillgruber, F., Krainitzki, H., Poobo, S., and Smith, F.H. (2002). The Neandertal type site revisited: interdisciplinary investigations of skeletal remains from the Neander Valley, Germany. Proc. Natl. Acad. Sci. USA 99, 13342-13347 5. Poobo, S., Higuchi, R.G., and Wilson, A.C. (1989). Ancient DNA and the polymerase chain reaction. J. Biol. Chem. 264, 9709-9712 Current Biology http://www.current-biology.com -------------------------------- Related Material: ANCIENT DNA AND THE ORIGIN OF MODERN HUMANS Notes by ScienceWeek: Mitochondria are double-membrane enclosed organelles of cells, the mitochondria involved with several important biochemical pathways, including electron transport and oxidative metabolism. Various types of cells containing internal membrane-bound organelles (eukaryotic cells) may contain from a few to several thousand mitochondria in each cell type. The mitochondria are relatively large cylindrical structures up to 10 microns long and up to 2 microns in diameter, and most biologists believe mitochondria are cell organelles that may have originated as separate organisms that became resident in eukaryotic cells. Mitochondrial DNA is independent of nuclear DNA, consisting of a circular molecule, 16,569 base pairs long in humans, with a known nucleotide sequence. Investigations of human mitochondrial DNA have revealed two facts relevant to questions of human origins: a) the variation among modern human populations is small compared, for example, to that between apes and monkeys, which has been interpreted to indicate the recency of human origins; b) there is a distinction between African and other human mitochondrial types, which has been interpreted to indicate the relative antiquity of the African peoples and the relative recency of other human populations. Interpretations of mitochondrial DNA evidence have been much debated in anthropology. Such evidence is a crucial part of the "single origin" model of human origins, which proposes that one early population of modern humans spread out of Africa approximately 60,000 to 100,000 years ago and eventually replaced all less modern populations of the genus Homo worldwide. Thus, the difference between "African" and "non-African" mitochondrial DNA is explained by the idea that small "founder" populations left Africa, carrying with them only a small sample of the genetic variation found in Africa as a whole, and that such founder populations then expanded as they occupied Eurasia, growing into a large population with a distinctly non-African mitochondrial DNA structure. This idea became popular in the late 1980s, when it was called the "Mitochondrial Eve" or "Out of Africa" hypothesis. Although since then this hypothesis has lost some support, it is still one of the major ideas concerning human origins. Support for the opposing "regional-continuity" model is based primarily on evidence of gradual morphological change, mainly of the skull, from ancient to modern inhabitants in different parts of the world. In this scenario, modern humans developed almost simultaneously in various geographical regions around the world, replacing less evolved Homo species beginning approximately 1.5 million years ago. These are only the general outlines of a hotly debated complex area of research in human evolution. The following points are made by G.J. Adcock et al (Proc. Nat. Acad. Sci.2001 98:537): 1) The authors point out that since its beginning more than 25 years ago, the debate over recent human origins has focused on two models. The regional-continuity hypothesis postulates that ever since humans began to migrate out of Africa more than 1.5 million years ago, there has been a single evolving species, Homo sapiens, distributed throughout the Old World, with all regional populations connected, as they are today, by gene flow. Some skeletal features developed and persisted for varying periods in the different regions, so that recognizable regional morphologies have developed in Africa, Europe, and Asia. 2) The other view, the "recent out of Africa" model, argues that over the period since humans began to leave Africa, there have been several species of Homo. In this model, H. sapiens emerged in Africa approximately 100,000 years ago and then spread globally, replacing other species of Homo that it encountered during the expansion. This model proposes that all current regional morphologies, especially those outside Africa, developed within the last 100,000 years. 3) These alternative models arose from interpretations of morphological evidence. During the last 15 years, molecular data, particularly nucleotide sequences drawn from populations of living humans, have made an increasing contribution to the debate. Analysis has demonstrated that humans have remarkably little mitochondrial DNA sequence variation, and that the earliest branching lineages are found in East Africa. These findings were interpreted as strongly supporting the "recent out of Africa" model. The authors suggest, however, that this interpretation fails to recognize that the demographic history of a species cannot be inferred from the pattern of variation of a single nucleotide segment. Patterns of variation in different regions of the genome must be considered and interpreted in the context of paleontological and archeological evidence. 4) The authors report mitochondrial DNA sequence evidence from 10 fossils, all agreed to be anatomically modern, rather than archaic, Homo sapiens (4 "*gracile" and 6 "*robust" specimens). The 10 fossils range in age from less than 10,000 years ago to approximately 60,000 years ago. The authors report that in one fossil (Lake Mungo 3, dated at 60,000 years ago), the mitochondrial DNA sequence is the most divergent of all of the Australian fossils analyzed, and this is evidently an example of a mitochondrial DNA lineage that existed in an ancient modern human but is absent in living human mitochondria. The authors state: "Our data present a serious challenge to interpretation of contemporary human mitochondrial DNA variation as supporting the 'recent out of Africa' model. A separate mitochondrial DNA lineage in an individual whose morphology is within the contemporary range and who lived in Australia would imply [from the out of Africa model and its usage of mitochondrial DNA data] both that anatomically modern humans were among those that were replaced and that part of the replacement occurred in Australia." In a commentary on this work, John H. Relethford (Proc. Nat. Acad. Sci. 1001 98:390) states: "If the mitochondrial DNA present in a modern human (Lake Mungo 3) can become extinct, then perhaps something similar happened to the mitochondrial DNA of *Neanderthals. If so, then the absence of Neanderthal mitochondrial DNA in living humans does not reject the possibility of /some/ genetic continuity with modern humans... The modern human origins debate can be informed by genetic data, both living and ancient, but can only be resolved by also considering the fossil and archeological evidence. The picture presented by Adcock et al suggests that modern human origins were more complicated than once envisioned." Proc. Nat. Acad. Sci. http://www.pnas.org -------------------------------- Notes by ScienceWeek: gracile: In general, a Homo fossil with a lightly built skull. The Lake Mungo 3 fossil is a gracile specimen. robust: In general, a Homo fossil with a heavily built skull. The human group we call the "Neanderthals" lived in much of Europe, part of Asia, and the Middle East between 150,000 to probably less than 30,000 years ago. Neanderthals were the first fossil humans to be discovered, and they have long been the focus of anthropological investigation. More bones of Neanderthals are known than for any other human-related (hominine) fossil group, including 30 nearly complete skeletons. ScienceWeek http://scienceweek.com Copyright © 2004 ScienceWeek All Rights Reserved US Library of Congress ISSN 1529-1472