middle pleistocene hominins

In contrast, the mandibular dentition of Jebel Irhoud 3, a juvenile late archaic hominin from Morocco dating to 160 ka with affinities to modern humans (Hublin; Hublin and Tillier), preserves evidence of a slower, modern pace of dental development (Smith et al). Genetic drift provides an alternative explanation for morphological divergence (Howell). Very wet and warm periods in Europe produced dense forests that may have also been unfavorable habitat (Roebroeks, Conard, and Van Kolfschoten), although interstadial periods seem to have been far more favorable for hominin populations than the coldest periods of glaciations. All extant mtDNA sequences coalesce to a common ancestor at 140-210 ka (Behar et al. The results showed that the most probable scenario (isolation and drift in the western and eastern populations of Neanderthals at 48 ka) would have involved an effective population size (Ne) of western Neanderthals of only 300 females, a marked reduction from the estimate for the eastern subpopulation ( females). Both African and European Middle Pleistocene hominins tended to be medium to tall in stature (Carretero et al) and very heavy for height relative to modern hunters and gatherers (Churchill et al; Kappelman). The biogeographic range reconstructions suggest the presence of a geographically widespread, mid-Pleistocene ancestor to humans, Neanderthals, H. heidelbergensis and H. rhodesiensis. Environmental and genetic data suggest that European hominins were primarily shaped by drift, while both factors operated in Africa. Both African and European Middle Pleistocene hominins tended to be medium to tall in stature (Carretero et al) and very heavy for height relative to modern hunters and gatherers (Churchill et al; Kappelman). Recently Martinón-Torres and colleagues have shown that the sample has very Neanderthal-like teeth; some of the nonmetrical features are even more common in the Sima de los Huesos sample than in late, “classic” Neanderthals from OIS 4 to OIS 3, which casts doubt on simple models of a steady increase in Neanderthal features over time. Analysis of autosomal DNA indicates a divergence time between modern human and Neanderthal populations of 270-440 ka (Reich et al). The usual cautions about the difference between census size and Ne apply, but one is left with the strong impression that western European Neanderthals experienced a major population crash during OIS 4. Drift slows in large populations but accelerates in small populations and can override the signal of all but the strongest selective pressures. Mellars and French have argued that Neanderthals in southwestern France had population numbers during the Würm Glaciation (OIS 4-3) that totaled approximately one-tenth (actually 1/9) as many individuals as the later Aurignacian occupation, although many of the assumptions that led to this conclusion have been challenged (Dogandηić and McPherron) and defended (Mellars and French). Perhaps the most critical problem has been an incomplete understanding of variation in skull form. As a result of this comparison of records of paleoclimate, morphological change, and genetic change, it seems apparent that many of the observed changes leading to Neanderthals were more likely to have been the products of drift than selection, whereas both drift and selection may have been important in the emergence of modern humans. Many of the key events appear to date to periods in which population sizes were greatly reduced and genetic drift would have been rapid. This period is associated with the first appearance of Homo heidelbergensis (or Homo rhodesiensis, if this name is to be preferred) in Africa (i.e., the Bodo cranium, dated to 600 ka; Clark et al; Rightmire) and, intriguingly, marked technological advances represented by precociously early blade production and core technology in the Kapthurin Formation at Lake Baringo (Johnson and McBrearty; Tryon and McBrearty). The climate in Europe in the Middle-Upper Pleistocene was dominated by a high-amplitude 100,000-year cycle that appears to have been determined by the eccentricity cycle in the earth’s orbit around the sun (deMenocal). The stature of early modern humans from the Levalloiso-Mousterian of the Levant and the Gravettian of Europe is particularly striking relative to Neanderthals and almost all other samples from Europe before the twentieth century (Carretero et al). The alternative, that genetic drift drove some or perhaps many of the anatomical changes, has long been recognized (Howell) but has received less emphasis. By continuing you agree to the use of cookies. Both African and European Middle Pleistocene hominins tended to be medium to tall in stature (Carretero et al. The implications of these findings are that contrary to previous conclusions (Ruff), pelvic form appeared to have followed a pattern of largely neutral evolution like most human cranial dimensions (Betti et al; Roseman; Weaver, Roseman, and Stringer). At the genetic level, two of the fundamental means by which evolution can occur are natural selection (referred to subsequently simply as “selection”) and genetic drift. The scale of the effect of climatic changes on human populations is clearly apparent in the dramatic decrease in the number of sites in the Last Glacial Maximum in East Africa (Brooks and Robertshaw); difficulties for human populations likely continued even after that, including evidence of the desiccation of Lake Victoria until ca. Over the last 50 years, the dominant view of the differences between Neanderthals and modern humans has been that the dissimilarities in anatomy reflected adaptive differences shaped by natural selection to meet specific challenges. By the end of that time span, Neanderthals and modern humans clearly differed physically and perhaps behaviorally. A short summary of this paper. Margins of error for dates for fossils or genetic events may overlap both favorable and unfavorable periods of climatic cycles. The dust core also indicates marked dry periods in East Africa during OIS 8 (301-242 ka), OIS 6 (186-127 ka), and OIS 4-2 (71-12 ka), although Blome et al. Periods of large-scale glacial advance in Europe should produce periods of stress and low population numbers and rapid genetic drift in Neanderthals. As a result, population size emerges as a key variable in both selection and drift. OIS 6 has been likened to the hyperarid conditions of the Last Glacial Maximum in OIS 2 (Deacon and Lancaster), which featured greatly decreased archaeological visibility of human populations in much of Africa (Brooks and Robertshaw). The resulting synthesis depicts a mosaic of wet and dry periods that are frequently asynchronous between regions and do not correspond in a consistent way to the OISs. Their results for East Africa are perhaps the most useful for inferences regarding the origin and dispersal of modern humans. In June, July, and August, clockwise-circulation monsoonal winds blow moisture onshore in Somalia from the Indian Ocean and carry dust from Somalia into the Arabian Sea. The best-fitting model produced a series of posterior estimates for demographic and historical parameters, including the age of the speciation event that produced modern humans (median: 141,455; 95% CI: 103,535-185,642), the age of the migration from Africa (median: 51,102; 95% CI: 40,135-70,937), the age of the colonization of the Americas (median: 10,280; 95% CI: 7,647-15,945), the size of the archaic African population (median: 12,772; 95% CI: 6,604-20,211), the population size during the bottleneck during speciation (median: 600; 95% CI: 76-1,620), the size of the bottleneck when leaving Africa (median: 462; 95% CI: 64-1,224), and the size of the bottleneck when leaving Asia to settle the Americas (median: 452; 95% CI: 71-1,280). One prominent example of this dependence on climate comes from mtDNA intramatch distributions that show rapid population growth in Africa at ca. ), and Y chromosomes coalesce at ka (Cruciani et al), although an extremely rare Y-chromosome haplotype from an African American man was recently reported that coalesces with other Y chromosomes at 338 ka (Mendez et al). However, the available archaeological evidence Site ODP 659, off of the coast of Mauritania and Western Sahara, receives a substantial amount of its dust from the southern Sahara and northern Sahel during these months. In a larger population, one expects more of the rare, favorable mutations to arise simply because the number of new mutations varies with population size (Cochran and Harpending; Hawks et al). For much of the last decade, palaeoanthropologists have been investigating the internal structure of the teeth of our ancient ancestors. Reviewing previous estimates of Neanderthal population numbers, Dennell, Martinón-Torres, and Bermúdez de Castro proposed the Neanderthal population of Europe totaled 3,000-5,000 during interstadials and 1,500-2,500 during the depths of glacial advances, when Neanderthal populations were confined to refugia in Iberia, Italy, and the Balkans. There is less agreement about the deeper phylogeny of these lineages and related forms from the late Lower through early Middle Pleistocene, but that period predates the central focus of this paper. This suite of Neanderthal features had become common in European hominins by OIS 5, including the specimens from Krapina and Saccopatore, and they became even more frequent in OIS 4-3. Traditionally, Middle Pleistocene hominin fossils that cannot be allocated to Homo erectus sensu lato or modern H. sapiens have been assigned to different specific taxa. Later populations display more derived features, and the skeletons from Qafzeh and Klasies River are near-modern in their morphology. The dust-flux record from the Arabian Sea, ODP 721/722, therefore records both of these influences. The age of the fossils from Sima de los Huesos is a key problem for making sense of the tempo and mode of hominin evolution in Europe over the last 500 kyr (Stringer). The last ENI, published in 2004, was 28. A second possibility for Europe is that the fossils from the Sima de los Huesos date to only around 350 ka. Copyright © 2021 Elsevier B.V. or its licensors or contributors. To read the full-text of this research, you can request a copy directly from the author. In this context, the Middle Pleistocene human dental assemblage from Atapuerca-Sima de los Huesos (SH) provides a unique opportunity to trace the evolution of enamel thickness in … In each case, populations can be inferred to have spread from regions with favorable climate and thus presumably comparatively high human population density into regions previously nearly devoid of people but with newly favorable climatic conditions. In the 1930s and 1940s, the German paleontologist G.H.R. von Koenigswald collected a number of Early-Middle Pleistocene hominid specimens in … Periods of decreased precipitation diminish the amount of vegetation and dependent biomass (including humans) and produce more dust. In contrast, periods of warmer but not yet heavily forested conditions would have supported a higher biomass of large herbivores and the humans who preyed on them (Roebroeks, Conard, and Van Kolfschoten), thus producing an increase in hominin population numbers and a decelerated rate of drift. 37 Full PDFs related to this paper. 14.5 ka (Williams et al) and the desiccation of Lake Tana around the same time (Lamb et al; Marshall et al). Describe the differences between middle Pleistocene hominins and Neandertals. If one accepts Bocquet-Appel et al.’s estimates for the Aurignacian and extends Mellars and French’s conclusions to the whole of Europe, it would imply that the Neanderthal population of Europe only totaled 492 individuals (95% CI: 193-3,151). Humans that are different from Homo erectus evolved first in Africa or western Eurasia. (Multiple answers) H. heidlebergensis has a mix of H. erectus and more dervied features which included a larger brain case, but it retained thicker browridges. It is difficult to tell whether this apparently late inflection in the rate of “Neanderthalization” was the result of selection within a large population during OIS 5 or of rapid drift in a small population during OIS 4-3. Recently, a number of authors have stressed that climatic deterioration in Europe and the Near East could have led to the local extinction of populations (Dennell, Martinón-Torres, and Bermúdez de Castro; Hublin and Roebroeks; Shea; Stewart and Stringer; Stringer). Large-brained hominins such as Upper Pleistocene Neandertals have evolved along their own evolutionary pathway and can be distinguished from modern humans in terms of growth pattern and brain development. Heinrich events, short periods of extreme cold followed by rapid warming, during glaciations may have posed especially difficult challenges for hominins in Europe (Stewart and Stringer and perhaps contributed to a contraction in the range of Neanderthals in southern Iberia and the spread of modern humans bearing Aurignacian technology into France and northern Spain (d’Errico and Sánchez Goñi). 350 ka) or old (500-600 ka) complicates scenarios for the pace of evolutionary change in Europe (Stringer). It is important to bear in mind that effective population size can be different from (and sometimes lower by an order of magnitude or more) census size (the actual number of individuals) and that Ne approximates the harmonic mean of the number of breeding individuals over time. Studies of the variation within H. erectus are followed by direct comparisons with the Middle Pleistocene population. This could have constrained human groups to migrate into such a propitious area. Hominins with the full suite of Neanderthal cranial traits appear by OIS 7 (Hublin), but a further pulse of change made western European Neanderthals from OIS 4-3 especially distinctive. In sum, this evidence suggests a speciation event in which The life-history pattern and brain ontogeny of extant humans emerged only recently in the course of human evolution. Using data from complete genomes of several modern men comprising two Yoruba, three Europeans, one Chinese, and one Korean, Li and Durbin applied population genetics models to infer changes in human effective population size over the last million years. Discriminant functions facilitate the description of intergroup differences. The glacial cycles show up very clearly in oxygen isotope values from deep-sea cores and ice cores from Greenland and Antarctica (deMenocal). However, there is no consensus concerning the tempo … Trinkaus argued that many distinctive facial features of Neanderthals and their relatively large canines and incisors were adaptations for increased amounts of anterior biting. suggest that this population also had a strikingly low long-term effective population size of approximately individuals for the period between 400 and 100 ka (Li, Patterson, and Reich. The two processes are not mutually exclusive, and both often act on a population at the same time. Neanderthals may have only rarely experienced periods of population growth and range expansion. A potential explanation for the apparent lack of a contraction in the effective population size of the ancestors of modern humans in Africa is that if there were in fact bottlenecks within a subdivided population in Africa, following the bottlenecks, members of dissimilar populations mixed extensively, restoring to the resulting population much of the genetic variation that existed before each bottleneck. The Chibanian, widely known by its previous designation of Middle Pleistocene, is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene epoch within the ongoing Quaternary period. Although Neandertals are the best-known fossil hominins, the tempo and evolutionary processes in their lineage are strongly debated. If the Sima de los Huesos dates to 500-600 ka (Bischoff et al), then one can conclude the features characteristic of the later, “classic” Neanderthals dating to OIS 4-3 increased in frequency very slowly within the Neanderthal lineage. Last: what about "classic Neandertals'" environment is assumed to help explain their morphological differences to other species? Both populations diverged from a common ancestor around 350,000 years ago as gauged by both genetic differences (Green et al.) hominins show the following: (i) wide bodies, a plesiomorphic char-acter in the genus Homo inherited from their early hominin ancestors; (ii) statures that can be found in modern human middle-latitude pop- ulations that first appeared 1.6–1.5 Mya; and (iii) large femoral heads in some individuals, a trait that first appeared during the middle Pleistocene in Africa and Europe. Their lineage are strongly debated 659 also receives dust from Western Sahara Kalahari. 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