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Post by Admin on Apr 22, 2022 20:09:25 GMT
Experts suggest Neanderthals are our closest extinct relative. In many ways, we’re alike: We are both hunter gatherers who have mastered the use of stone tools and weapons. But experts also agree that we have our differences. Those differences are seen in a split from a common ancestor more than half a million years ago. Still, the species that connects us has long eluded scientists. Experts thought Homo heidelbergensis was the missing link — an early human species known to be the first to build shelters — but newer research has called this theory into question. The age of H. heidelbergensis fossils revealed that some of the specimens were too young to be the common ancestor, says Chris Stringer, a paleoanthropologist at the London Natural History Museum. Rather, H. heidelbergensis was more likely a contemporary of modern humans and Neanderthals, not an ancestral link, says Stringer. "Frankly, we no longer know where the ancestry of the Neanderthal lies," he says. Laser Dating Technology Experts think that a common ancestor goes back to around 600,000 years ago, far older than Kabwe 1, for example, a H. heidelbergensis skull found in Zambia in 1921. In the study published last year, Stringer and his team used laser dating to uncover that the skull, which was formerly thought to be much older, was only around 300,000 years old. This was when both modern humans and Neanderthals already existed. Laser dating technology helped experts to uncover who our common ancestor was not. But it will take similar, more advanced technology, to finally pinpoint the link. We must look back even further into the fossil record to unlock the mystery and we’re not there yet, says Stringer. "When we have a better fossil record from around 500,000 to 800,000 years ago, we’ll be in a better position to know for sure." The Human and Neanderthal Split To find this common ancestor, experts must uncover when the split occurred. The earliest known examples of Neanderthal fossils date back to around 430,000 years ago. The oldest Homo sapiens fossils date back to 300,000 years ago, but Stringer says that older modern human remains are still to be found. The warm climate in Africa, where the earliest H. sapiens lived, has impacted the preservation of DNA more than Neanderthal remains found further north in Europe and Asia, he says. Researchers use DNA evidence when they can, but when it’s not available, they rely on anatomy to note the differences between Neanderthals and H. sapiens. Humans have a high and rounded brain case, with a small brow, a chin on the lower jaw and a slimmer bone structure, says Stringer. Neanderthals, by comparison, have a longer, lower skull, with a larger nose, brow and no chin. "Humans have a clearly distinct skeletal shape from Neanderthals," says Stringer. "These differences suggest that there was a separate evolution for hundreds of thousands of years." On the other hand, older modern human remains have a bigger brow, bulkier teeth and more robust skeletons. And the closer in age the remains are to the mystery ancestor, the difference in features is less pronounced. After the two species evolved from a common ancestor, they became unmistakably separate in both appearance and DNA. But at the same time, before Neanderthals went extinct 40,000 years ago, they did many of the same things as humans. They hunted the same large game, had burial rituals, used similar tools and even interbred. "We can’t know whether it was coerced or not, but we do know they interbred," says Erella Hovers, a professor of prehistoric archaeology at the Hebrew University of Jerusalem. No matter whether it was through love or war, says Hovers, we still hold the remnants of Neanderthals in our genes today. Depending on what part of the world you call home, you likely have around two percent Neanderthal DNA.
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Post by Admin on Apr 22, 2022 21:14:35 GMT
The status of Homo heidelbergensis (Schoetensack 1908) Chris Stringer First published: 20 June 2012 doi.org/10.1002/evan.21311Abstract The species Homo heidelbergensis is central to many discussions about recent human evolution. For some workers, it was the last common ancestor for the subsequent species Homo sapiens and Homo neanderthalensis; others regard it as only a European form, giving rise to the Neanderthals. Following the impact of recent genomic studies indicating hybridization between modern humans and both Neanderthals and “Denisovans”, the status of these as separate taxa is now under discussion. Accordingly, clarifying the status of Homo heidelbergensis is fundamental to the debate about modern human origins. © 2012 Wiley Periodicals, Inc. THE SPECIES HOMO HEIDELBERGENSIS In 1907, the robustly built mandible that was to become the holotype of Homo heidelbergensis was discovered in the Grafenrain sandpit at Mauer, near Heidelberg, Germany, associated with what is now termed a Galerian or Cromerian (early Middle Pleistocene) fauna. The species name was bestowed a year later by Otto Schoetensack,1 who noted in the Mauer mandible the combination of primitive features (for example, high corpus thickness, very wide ramus, and receding symphysis) and more recent human features, such as small dentition, particularly the canines and anterior teeth. The name was little used during the earlier part of the twentieth century and, by the 1960s the lumping together of taxa often treated the fossil as a European form of Homo erectus.2 However, Howell3 took exception to that, arguing that the fossil probably was morphologically distinct enough to represent a separate species. In 1974, I completed my doctoral thesis, which concentrated on cranial shape comparisons of Neanderthal and modern humans but, along the way, I noted clear phenetic resemblances between the Broken Hill (Zambia) and Petralona (Greece) fossils, and considered both of these to be clearly distinct from Neanderthals.4, 5 Rather than allocate either of these specimens to Homoerectus, I preferred, at that time, to regard them as related primitive forms of Homosapienssensu lato, eventually assigning them to Homosapiens grade 1 in a gradistic scheme.6 Following discussions with Bjorn Kurtén, I became aware of biostratigraphic evidence that elements of the Petralona mammalian faunas were of Cromerian age, potentially comparable to those from Mauer.7 Both Kurtén and I considered the possibility that the Petralona cranium could represent a counterpart for the Mauer mandible,6, 8 even though the two clearly do not articulate well. In the early 1980s, with a shift to cladistic thinking and influences, I began to gravitate toward the idea that Neanderthals were, after all, a distinct species from Homosapienssensu stricto, and that this implied the existence of a distinct ancestral species, if neanderthalensis and sapiens were sister taxa, and erectus did not represent the last common ancestor. Through linking Mauer with Petralona and Petralona with Broken Hill, the concept of a Eurafrican stem species named Homoheidelbergensis began to develop.9 The following extract and accompanying figure (Fig. 1) summarize the cautious arguments made at that time: “Because at present they cannot be defined satisfactorily by their own distinctive within-group characteristics, it is difficult to justify creating a separate taxon for the Petralona and Broken Hill fossils on the basis of characters they lack, or ones they share with other taxa. Nevertheless, given the need to recognize their similarities to each other, and to other Middle Pleistocene fossils, they could be placed in a separate species, H. rhodesiensis or H. heidelbergensis (if the Mauer mandible is also included), provided the distinctiveness of the Neanderthals from ‘modern’ H. sapiens is also considered worthy of specific recognition (Fig. 1a). Alternatively their possible position as a ‘stem group’ for the Upper Pleistocene hominids could be recognized by the use of a subspecific name for the evolutionary grade they are supposed to represent within H. sapiens (Fig. 1b). However, the other possibility that must be considered (Fig. 1c) is that we cannot at present resolve the exact phylogenetic position of these hominids because they are close to the point of divergence between Neanderthals and ‘modern’ H. sapiens (assuming that the Neanderthals are not directly ancestral to ‘modern’ humans). At present I believe this to be quite likely, and that these fossils are close to the morphotype expected in the common ancestor of Neanderthals and ‘modern’ H. sapiens. If this is so, only further careful analysis will allow a decision about the cladistic affinities, and thus the classification, of fossils such as Arago 21, Petralona and Broken Hill.”
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Post by Admin on Apr 22, 2022 21:57:56 GMT
Figure 1 Illustration of the possible phylogenetic relationships of the Petralona and Broken Hill fossils. Redrawn, with permission, from Stringer.9 I began to develop a suite of traits (Table 1; Fig. 2) for grouping Broken Hill and Petralona.10 European and African fossils such as Bilzingsleben, Vertesszöllös, Bodo 1, and Elandsfontein were added to an enlarged heidelbergensis hypodigm. A separate study of the first Bilzingsleben cranial finds reinforced their resemblance to the Elandsfontein calvaria,11 and the possibility that Middle Pleistocene Chinese and Indian fossils might also belong in this group (Table 2) was raised.12, 13 Rightmire has adopted a comparable Eurafrican concept of heidelbergensis,14, 15 while some have preferred to retain a more gradistic concept of Homosapiens, arguing that fossils such as Broken Hill and Bodo are primitive examples of the modern human species.16 Other workers have used the informal term ante- or preneanderthal for earlier European fossils, including Mauer and Arago, sometimes with a purely chronological meaning, and in other cases implying an evolutionary relationship.17 Table 1. Some Traits Observed in H. heidelbergensis Fossils Endocranial volumes overlap those of H. erectus and H. sapiens/H. neanderthalensis Torus often highly pneumatized laterally, and superiorly into frontal squama Vault shape parallel-sided in posterior view Strong and continuous supraorbital torus* Occipital bone strongly angled* Strong continuous occipital torus* Wide interorbital breadth* Iliac pillar* Elongated superior pubic ramus*# Femoral platymeria*# High arched temporal squama+# Gracile tympanic+# Increased midfacial projection expressed through measures of midline nasal prominence+# In large-faced specimens there may be lack of both canine fossa and infraorbital retraction# Reduced total facial prognathism+# *Found in Homo erectus; + potential synapomorphies with H. sapiens; # potential synapomorphies with H. neanderthalensis. Table 2. Some Fossils That May Represent Homo heidelbergensis* Western Eurasia Mauer Petralona Arago Vértesszöllös ?Bilzingsleben ?Kocabaş ?Boxgrove ?Ceprano ?Zuttiyeh Africa Broken Hill 1; tibia E.691; pelvis E.719 Bodo Elandsfontein Ndutu Kapthurin ?Hoedjies punt ?Thomas Quarry ?Salé ?Tighenif ?Berg Aukas Eastern Eurasia ?Narmada ?Dali ?Jinniushan ?Yunxian *In my view, the inclusion of fossils such as Steinheim and Montmaurin is still doubtful, while Narmada, Dali and Jinniushan may alternatively represent early “Denisovans.” This latter option has become increasingly popular with the recognition that the Sima de los Huesos (SH) material displays a mosaic of heidelbergensis and neanderthalensis features. For such workers, H. heidelbergensis could represent an early stage in the accretion model of Neanderthal evolution,17, 18, 35 forming a heidelbergensis-neanderthalensis continuum. I briefly considered this argument, going so far as to suggest that all heidelbergensis material might be lumped into Homoneanderthalensis,19 but I did not persist in that view. However, if the European-only model of heidelbergensis is correct, then the non-European components assigned to heidelbergensis by workers such as Rightmire and me, which show few or no Neanderthal apomorphies, would require a separate species names. Homorhodesiensis20 would have priority for that grouping.9, 21
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Post by Admin on Apr 23, 2022 0:42:24 GMT
RECENT RESEARCH ON THE MAUER MANDIBLE, AND THE SPECIES HYPODIGM Recently, welcome attention has been given to the Mauer mandible itself, including further dating work.22 Schwartz and Tattersall23 compared its morphology with that of other Pleistocene hominins, noting its particular resemblance to the Arago 13 mandible. Via the Arago assemblage, they were able to extend their heidelbergensis grouping to other European, Chinese, and African fossils, while aligning the SH material with Neanderthals. However, in their view, the derived natures of both the Neanderthal clade and Homoheidelbergensis exclude these groups from the ancestry of Homosapiens.
Rak and colleagues41 noted the idiosyncratic features of the Mauer jaw and argued that “it is not clear whether lumping certain specimens together in this hypodigm is justified at all. In effect, the morphology of certain specimens does not accord with that of the type specimen. Obviously, the taxonomic identification of skulls lacking a mandible is problematic, but even some mandibles give rise to uncertainty regarding their assignment to the H. heidelbergensis hypodigm. In our analysis, the Mauer mandible stands alone in its morphology, which appears to be the outcome of a unique constellation of characters.” This mirrored the view of Hublin,21 who argued that the primitive nature of the Mauer mandible and the predominance of cranial material in discussions about Middle Pleistocene hominins rendered it unsuitable as a holotype.
In the most extensive comparative analysis to date, Mounier, Marchal, and Condemi24 concluded that the Mauer mandible and H. heidelbergensis could be specifically distinguished from H. erectus, H. neanderthalensis, and H. sapiens. They produced a diagnosis for the species hypodigm based on mandibular fossils such Mauer, Arago, Montmaurin, and SH. Their inclusion of the Tighenif mandibles extended the species to Africa, but unfortunately they did not include other potential African examples of heidelbergensis, such as Thomas Quarry and Kapthurin, in their analyses. However, it is worth remembering that a fragment of ramus found at Elandsfontein, possibly associated with the “Saldanha” calvaria, was noted as being remarkably similar to that of Mauer in its shape.25
As mentioned, researchers using metric and multivariate techniques have noted metrical and shape similarities between Petralona and Broken Hill.5, 14, 26 This has been confirmed through the use of geometric morphometrics.27, 28 For example, Friess,28 excluding the Mauer mandible, commented that “the striking affinities between the holotype of H. rhodesiensis (Kabwe) and a European fossil (Petralona), as demonstrated previously and confirmed here, are unlikely to disappear, even if more complete specimens were to be included in the analysis. This makes H. rhodesiensis an Afro-European species that retains an erectus-like plesiomorphic calvarial shape, but no Neandertal/H. sapiens apomorphies, unless one lumps it with SH5 and Steinheim.” In a further study, Mounier, Condemni, and Manzi29 added the Ceprano calvaria to their comparative analyses. They grouped the Ceprano specimen with Eurasian fossils such as Petralona, SH5, Steinheim, Dali, and Jinniushan, as well as with the Broken Hill cranium. They concluded that in spite of its relatively young chronological age (385-430 ka), the Ceprano fossil could represent a morphologically primitive example of the widely dispersed species heidelbergensis.
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Post by Admin on Apr 23, 2022 18:01:35 GMT
ARE THE SIMA DE LOS HUESOS FOSSILS PART OF HEIDELBERGENSIS? Although Mounier and coworkers24, 29 felt able to include the SH material in their heidelbergensis hypodigm, I believe that this inclusion has led to the most serious confusion surrounding the status of the species. From the first detailed descriptions of the Sima fossils, their combination of heidelbergensis-like and Neanderthal-like features has been recognized.19 Increasingly old age estimates for the SH assemblage (now >530 ka30, 31) have reinforced the Atapuerca team's preference for assigning the material to heidelbergensis. However, for some time I have preferred to regard the SH material as an archaic form of neanderthalensis,13 based on the presence of Neanderthal-like features such as an incipient suprainiac fossa and midfacial projection in the crania, dental and mandibular traits, and numerous postcranial characters. More recently, I have also challenged the older age estimates obtained for the SH sample from a dated speleothem.32 That challenge was based on taphonomic issues rather than the age determination itself, but dating work on the speleothem is continuing (J.-L. Arsuaga, personal communication). Recently, even stronger reasons have emerged to place the SH material within the Neanderthal clade rather than within heidelbergensis. Regardless of those considerations, morphological and genetic data suggest that the divergence of the neanderthalensis and sapiens lineages very likely postdates 530 ka. Therefore, Neanderthal apomorphies would not be expected at such an antiquity. Comparisons using the draft Neanderthal genome produced the following estimate: “Assuming that human-chimpanzee average DNA sequence divergence was 5.6 to 8.3 million years ago, this suggests that Neandertals and present-day human populations separated between 270,000 and 440,000 years ago.”33 Using only complete mtDNA sequences, Endicott, Ho, and Stringer32 argued that “our genetic date estimates are inconsistent with the late Early Pleistocene, early Middle Pleistocene, and late Middle Pleistocene models for the divergence between H. sapiens and H. neanderthalensis.... Rejection of these three models leaves just the mid-Middle Pleistocene model for the time of divergence between modern humans and Neanderthals…. Here, our 95% credible intervals for the MRCA [most recent common ancestor] (315-538 ka) fall squarely within the proposed dates from palaeoanthropology.... Our estimates are also consistent with dates derived from analysis of neutral morphological characters in both species, 182-592 ka (mean 373 ka).34” Recently, even stronger reasons have emerged to place the SH material within the Neanderthal clade rather than within heidelbergensis. Data from the large SH dental sample have long suggested Neanderthal affinities.35 Most recently, Martinón-Torres and colleagues36 concluded: “We find that SH dentitions present all the morphological traits that, either in their degree of expression, frequency, or particular combination, are usually considered as typical of Homoneanderthalensis. This study ratifies the deep roots of the Neanderthal lineage in the Middle Pleistocene of Europe. In addition, SH teeth are morphologically ‘more Neanderthal’ than other penecontemporaneous Middle Pleistocene samples such as Mauer or Arago, and even more derived than some classic Neanderthal samples.” Because they adhere to an age of >530 ka for the SH sample, these authors are forced to add, “Thus, our study would not sustain the linearity of the accretion process hypothesized for the origins of the Neanderthals, and we suggest that other evolutionary models and scenarios should be explored for the Middle and Upper Pleistocene of Europe. We propose that more than one hominin lineage may have coexisted during the Middle Pleistocene in Europe.” While I agree with that last statement, it is on completely different grounds. Martinón-Torres and coworkers35 argue for this on the basis of an (in my view erroneous) early date for neanderthalensis (SH) characteristics. I would instead argue for coexistence on the basis of late heidelbergensis age estimates within and outside of Europe.29, 37-40 In addition, it may well be that significant Neanderthal-like samples such as Krapina, considered to be relatively late in the European sequence, are older than is currently believed (R. Grün and C. Stringer, unpublished research). Rak and coworkers41 have recently added to the data that the SH material is predominantly Neanderthal in its affinities: “The claimed similarities between the characters of the Mauer specimen…and those of Neandertals and the Sima de los Huesos mandibles…cannot be considered homologous, and hence, they are not synapomorphies. Although some of the Mauer characters superficially resemble the ones on the Neandertal and Sima specimens, the Mauer characters stem from a different morphological configuration. On the other hand, the similarities between the Neandertal characters and those of the Sima mandibles are the outcome of identical configurations, making these characters true synapomorphies.” This was reinforced as follows: “The study of mandibles from Sima de los Huesos reveals an identical morphology to that of the corresponding and unique region in the Homo neanderthalensis mandible.... This constellation of characters is absent in other early and late hominins, including the type specimen Homo heidelbergensis (the Mauer mandible).... We conclude that the mandibles of the Sima sample are virtually identical to the Neandertal mandible. Thus, we regard this morphology as a synapomorphy that the Sima fossils share only with H. neanderthalensis. In some other cranial morphologies, the Sima sample does not resemble Neandertals; hence, we place the Sima specimens within the Neandertal clade as a sister group to Neandertals. This conclusion is inevitable regardless of whether one advocates a cladogenetic or anagenetic model.”42 The Sima de los Huesos (Burgos, northern Spain): palaeoenvironment and habitats of Homo heidelbergensis during the Middle Pleistocene
Abstract Interpreting how environmental dynamics respond to global climate change and how this has affected human evolution and dispersal is an on-going topic of debate. During the early Middle Pleistocene (∼0.6–0.4 Ma), as compared to earlier, environmental conditions were relatively more stable, with longer climatic cycles alternating between open and forested landscapes. During this interval, humans spread successfully providing an important number of fossil sites where fossils or tools are reported. The Atapuerca-Sima de los Huesos (Burgos, northern Spain) site (Atapuerca-SH) is one of the earliest localities with hominin evidence in the European Middle Pleistocene, with the most important accumulation of Homo heidelbergensis so far. We have analyzed the abundant faunal record from Sima de los Huesos, which is mainly comprised of carnivores, in order to approach an interpretation of the palaeoenvironmental circumstances where these hominids inhabited within the Sierra. Other sites from Sierra de Atapuerca referred to the same Faunal Unit (FU 6), are roughly contemporaneous, and include important ungulates, which are here analyzed with Atapuerca-SH. Additional information provided by isotopic analysis helps elucidate the ancient ecology of taxa present in Sima de los Huesos allowing for an accurate portrayal of the setting in which humans lived. The timing of the spread of Homo heidelbergensis is dominated by a relative climatic and environmental stability and points to a landscape dominated by savannah-like open woodland.
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