The stem species of our species: a place for the archaic human cranium from Ceprano, Italy

One of the present challenges in the study of human evolution is to recognize the hominin taxon that was ancestral to Homo sapiens. Some researchers regard H. heidelbergensis as the stem species involved in the evolutionary divergence leading to the emergence of H. sapiens in Africa, and to the evolution of the Neandertals in Europe. Nevertheless, the diagnosis and hypodigm of H. heidelbergensis still remain to be clarified. Here we evaluate the morphology of the incomplete cranium (calvarium) known as Ceprano whose age has been recently revised to the mid of the Middle Pleistocene, so as to test whether this specimen may be included in H. heidelbergensis. The analyses were performed according to a phenetic routine including geometric morphometrics and the evaluation of diagnostic discrete traits. The results strongly support the uniqueness of H. heidelbergensis on a wide geographical horizon, including both Eurasia and Africa. In this framework, the Ceprano calvarium--with its peculiar combination of archaic and derived traits--may represent, better than other penecontemporaneous specimens, an appropriate ancestral stock of this species, preceding the appearance of regional autapomorphic features.     

A comparative study of frontal bone morphology among Pleistocene hominin fossil groups

Features of the frontal bone that are conventionally used to distinguish among fossil hominin groups were quantitatively examined. Fifty-five fossil crania dating from the early to the late Pleistocene were analyzed. Using a modified pantograph, outlines of the frontal bone were collected along the midsagittal and two parasagittal planes. The profile from nasion to bregma, as well as two profiles above the medial and lateral sections of the orbit, respectively, extending from the orbital margin to the coronal suture were traced. The outlines were measured using Elliptical Fourier Function Analysis (EFFA), which enabled a quantification of aspects of the frontal bone that have historically been described primarily in nonmetric or linear terms. Four measurements were obtained: 1) overall morphology as expressed in the Fourier harmonic amplitudes; 2) maximum projection of the supraorbital torus at three points along the browridge (glabella and the medial and lateral aspects of the torus above the orbit); 3) maximum distance of the frontal squama from the frontal chord, capturing forehead curvature; and 4) nasion-bregma chord length. The results indicate that the midsagittal profile is significantly different among all Pleistocene groups in analyses that include both size and shape, as well as size-adjusted data. Homo erectus is significantly different from the late Pleistocene groups (Neandertals and early modern H. sapiens) in glabellar projection. Anatomically modern humans are significantly different from all other groups in both raw and size-standardized analyses of all three outlines that captured overall morphology, as well as forehead curvature and lateral supraorbital torus prominence, and middle Pleistocene Homo are significantly different in both medial and lateral overall parasagittal form. However, for the majority of analyses there were no significant differences among the Pleistocene archaic groups in supraorbital torus projection, frontal squama curvature, nasion-bregma chord length, or overall frontal bone morphology.     

Out of the North Sea: the Zeeland Ridges Neandertal

In 2001, a portion of human frontal bone was discovered in sediments extracted from the bottom of the North Sea, 15 km off the coast of the Netherlands. The extraction zone is located in the so-called Zeeland Ridges area located at 51°40′ northern latitude and 3°20′ eastern longitude. The specimen was dredged up from sediments containing Late Pleistocene faunal remains and Middle Palaeolithic artefacts, including well-finished small handaxes and Levallois flakes. The details of the supraorbital morphology, as well as the quantitative assessment of the shape of the external surface of the squama using traditional and 3D geometric morphometrics, unambiguously assign the Zeeland Ridges frontal bone to Homo neanderthalensis. Carbon and nitrogen isotopic analysis indicate that the Zeeland Ridges hominin, like other Neandertals, was highly carnivorous and does not show evidence for the consumption of aquatic foods. A lesion on the outer table and diploic layer of the bone in the area of the supratoral sulcus can be interpreted as the result of an intradiploic epidermoid cyst, a type of neoplasm diagnosed for the first time in Neandertal remains. So far, the Zeeland Ridges Neandertal is the first Pleistocene fossil hominin found under seawater and the first recorded in the Netherlands.     

中更新世非洲Bodo人类头骨化石与周口店直立人的比较--中国与非洲人类头骨特征对比之三

发现于埃塞俄比亚MiddleAwash地区Bodo地点距今60万年的人类头骨化石是迄今发现的最为古老和完整的非洲中更新世人类化石。由于Bodo头骨化石在形态特征上兼有直立人与智人的特点,多年来学术界对其分类地位一直存在争议。Rightmire认为Bodo头骨化石与BrokenHill及Petralona等在分类上属于古老型智人的中更新世人类更为接近,是非洲直立人向古老型智人过渡的代表。至少在距今60万年的中更新世早期直立人向古老型智人转变的成种事件在非洲就已经发生。以Bodo头骨为代表的一批更新世中期非洲和欧洲人类化石构成了可能是后期人类祖先的人属海德堡种。这些观点导致了近年学术界对古老型智人在非洲及欧亚出现时间以及更新世中期非洲和欧亚地区古人类相互之间演化关系的关注。基于这样的背景,本文对年代与Bodo化石接近的周口店直立人头骨特征与Bodo头骨的相似及差异表现情况进行了对比研究。结果发现Bodo头骨在一系列特征上与周口店直立人相似,同时在包括颅容量在内的其它一些特征上呈现出后期智人的特点,但总体形态上似乎与直立人更为相似。作者认为尽管这种进化上的镶嵌现象在中国古人类化石记录上也广泛存在,但由于中国人类化石标本在年代上的不确定性,目前还没有可靠的证据说明这种集直立人与智人化石特征为一体的镶嵌性在中国古人类化石出现的时间接近或早于非洲。考虑到中国与非洲直立人生存年代的巨大差异及人类演化的不同步或地区间差异,具有较多后期人类特征表现的人类首先出现在非洲是完全可能的。根据这些研究对比,作者就人类演化的镶嵌现象、更新世中期非洲与亚洲地区人类演化上的差异等问题进行了讨论。     

New Radiometric Ages for the BH-1 Hominin from Balanica (Serbia): Implications for Understanding the Role of the Balkans in Middle Pleistocene Human Evolution

Newly obtained ages, based on electron spin resonance combined with uranium series isotopic analysis, and infrared/post-infrared luminescence dating, provide a minimum age that lies between 397 and 525 ka for the hominin mandible BH-1 from Mala Balanica cave, Serbia. This confirms it as the easternmost hominin specimen in Europe dated to the Middle Pleistocene. Inferences drawn from the morphology of the mandible BH-1 place it outside currently observed variation of European Homo heidelbergensis. The lack of derived Neandertal traits in BH-1 and its contemporary specimens in Southeast Europe, such as Kocabaş, Vasogliano and Ceprano, coupled with Middle Pleistocene synapomorphies, suggests different evolutionary forces acting in the east of the continent where isolation did not play such an important role during glaciations.     

The ATD6-5 mandibular specimen from Gran Dolina (Atapuerca, Spain). Morphological study and phylogenetic implications.

Metric and shape features of the Lower Pleistocene mandibular specimen ATD605 from the level 6 of Gran Dolina site (Atapuerca, Spain) are compared with a large sample of fossil hominid mandibles. The analysis shows that ATD6-5 displays a generalized morphology largely shared with both African and European Lower and Middle Pleistocene samples. However, distinctive African traits, such as corpus robustness and strong alveolar prominence, are absent in the Gran Dolina specimen. At the same time, none of the apomorphic features that characterize Middle and early Upper Pleistocene European hominids can be recognized in ATD6-5. Finally, the Gran Dolina specimen displays a remarkable position of the mylohyoid groove, only comparable to that found in immature specimens of Homo ergaster, and very rarely in adult H. sapiens. The morphology of ATD6-5 supports the hypothesis of an African origin for the first Europeans with subsequent phylogenetic continuity with Middle Pleistocene populations in Europe. These findings are consistent with H. antecessor being the last common ancestor of Neandertals and H. sapiens.     

The Neanderthal "chignon": variation, integration, and homology

The occipital bun ("chignon") is cited widely as a Neanderthal derived trait. It encompasses the posterior projection/convexity of the occipital squama and is associated with lambdoid flattening on the parietal. A 'hemibun' in some Upper Paleolithic Europeans is thought by some authors to indicate interbreeding between Neanderthals and early modern Europeans. However, 'bunning' is difficult to measure, and the term has been applied to a range of morphological patterns. Furthermore, its usefulness in phylogenetic reconstruction and its homologous status across modern and fossil humans have been disputed. We present a geometric morphometric study that quantitatively evaluates the chignon, assesses its usefulness in separating Neanderthals from modern humans, and its degree of similarity to Upper Paleolithic 'hemibuns.' We measured the three-dimensional coordinates of closely spaced points along the midsagittal plane from bregma to inion and of anatomical landmarks in a large series of recent human crania and several Middle and Late Pleistocene European and African fossils. These coordinate data were processed using the techniques of geometric morphometrics and analyzed with relative warps, canonical variates, and singular warps. Our results show no separation between Neanderthals and modern humans, including early modern Europeans, when the shape of the occipital plane midsagittal-profile is considered alone. On the other hand, Neanderthals are well separated from both recent and fossil modern humans when information about the occipital's relative position and relative size are also included. Furthermore, the occurrence of a highly convex and posteriorly projecting midline occipital profile (interpreted as the occipital bun) is highly correlated (>0.8) with a flat parietal midsagittal profile and with antero-superiorly positioned temporal bones across both our recent and our fossil human samples. We conclude that the shape of the occipital profile alone should not be considered an independent trait, as it is very tightly integrated with braincase shape. Our analysis does not support differences in integration of the posterior midsagittal profile and the cranial base in Pleistocene and recent humans.     

Geometric morphometric analysis of the crown morphology of the lower first premolar of hominins, with special attention to Pleistocene Homo

This article is the third of a series that explores hominin dental crown morphology by means of geometric morphometrics. After the analysis of the lower second premolar and the upper first molar crown shapes, we apply the same technique to lower first premolar morphology. Our results show a clear distinction between the morphology seen in earlier hominin taxa such as Australopithecus and African early Homo, as well as Asian H. erectus, and more recent groups such as European H. heidelbergensis, H. neanderthalensis, and H. sapiens. The morphology of the earlier hominins includes an asymmetrical outline, a conspicuous talonid, and an occlusal polygon that tends to be large. The morphology of the recent hominins includes a symmetrical outline and a reduced or absent talonid. Within this later group, premolars belonging to H. heidelbergensis and H. neanderthalensis tend to possess a small and mesiolingually-displaced occlusal polygon, whereas H. sapiens specimens usually present expanded and centered occlusal polygons in an almost circular outline. The morphological differences among Paranthropus, Australopithecus, and African early Homo as studied here are small and evolutionarily less significant compared to the differences between the earlier and later homin taxa. In contrast to the lower second premolar and the upper first molar crown, the inclusion of a larger hominin sample of lower first premolars reveals a large allometric component.     

Geometric variation of the frontal squama in the genus homo: Frontal bulging and the origin of modern human morphology

The majority of studies of frontal bone morphology in paleoanthropology have analyzed the frontal squama and the browridge as a single unit, mixing information from different functional elements. Taking into account that the bulging of the frontal bone is often described as a species‐specific trait of Homo sapiens, in this article we analyze variation in the midsagittal profile of the genus Homo, focusing on the frontal squama alone, using landmark‐based superimpositions and principal components analysis. Our results demonstrate that anatomically modern humans are definitely separated from extinct human taxa on the basis of frontal bulging. However, there is minor overlap among these groups, indicating that it is necessary to exercise caution when using this trait alone to make taxonomic inferences on individual specimens. Early modern humans do not show differences with recent modern humans, and “transitional” individuals such as Jebel Irhoud 1, Maba, and Florisbad, show modern‐like frontal squama morphology. The bulging of the frontal squama in modern humans may represent a structural consequence of more general cranial changes, or it could be a response to changes in the morphology of the underlying prefrontal brain elements. A subtle difference between Neandertals and the Afro‐European Middle Pleistocene Homo sample is associated with flattening at bregma in the former group, a result that merits further investigation. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc     

安徽东至华龙洞出土的人类化石

2006年在安徽省东至县华龙洞发现了1枚人类下颌第二臼齿和2件可以拼接在一起的额骨碎片化石。根据华龙洞动物群组成及地层情况,初步确定华龙洞化石层的时代为更新世中期。本文对在华龙洞发现的人类头骨和牙齿化石的形态特征进行了观测,并与相关古人类标本进行了对比。研究发现:华龙洞人额骨和下颌臼齿都呈现出一系列常见于东亚直立人的特征。华龙洞额骨曲度较小,具有粗壮的颞线和较厚的骨壁。此外,华龙洞额骨还具有额中缝结构和扩大的额窦。华龙洞下颌第二臼齿总体显得比较粗壮。齿冠咬合面具有第五尖、第六尖和第七尖。齿冠尺寸明显大于早期现代人、现代人类和欧洲更新世中期人类,位于直立人变异范围。结合对华龙洞人类额骨和牙齿形态对比所揭示的形态特点,在华龙洞发现的人类化石可能代表着生活在更新世中期的直立人。     

Palaeopathological and variant conditions of the Homo heidelbergensis type specimen (Mauer,Germany)

Although early Homo specimens are now known from a number of African, Asian and European Middle Pleistocene sites, the taxon Homo heidelbergensis was initially introduced for the Mauer jaw recovered in 1907. Fossil hominids from the earlier Middle Pleistocene of Europe are very rare and the Mauer mandible is generally accepted as one of the most ancient, with an age of approximately 700 kyr. A new preparation of the mandible was conducted in 1996 and gave rise to the detailed palaeopathological examination which is presented here. Based on comparative analyses, the extreme breadth of the mandibular ramus and its flat intercondylar incision, in conjunction with the flattening and broadening of the coronoid process tip, results either from an idiosyncratic pattern of the course and insertion of the temporalis muscle on the coronoid process or from the temporalis possessing an accessory head. The incidence of periodontal pocketing, together with a vertical reduction of the alveolar margin to approximately 3.00 mm, and a slight protuberance formed in vicinity of the right M(2)can safely be interpreted as pathognomonic indications of periodontal disease. The short distance between the enamel-dentine junction of the teeth and the horizontal alveolar margins could either be an inherited variant or may result from incipient osteoporosis. In addition, an arthrotic condition with slight osteophytic peripheral exostoses and an arthrolit (i.e. an articular calculus or "joint mouse") on the left condylus articularisand a depression in the medial part of the left mandibular condyle extending into the inferior part of the ramus are present. These features are indicative of a trauma-induced osteochondrosis dissecans. The diagnosis therefore suggests that the observed depression results from a well-healed fracture. This traumatic event illustrates the demanding living conditions endured by humans during the European Middle Pleistocene. The variations and pathological conditions observed in Mauer do not question the mandible's role as type specimen for the taxon Homo heidelbergensis.     

Endocranial capacity of the bodo cranium determined from three-dimensional computed tomography

The 600,000-year-old cranium from Bodo, Ethiopia, is the oldest and most complete early Middle Pleistocene hominid skull from Africa. "Virtual endocast" models created by three-dimensional computed tomography (CT) techniques indicate an endocranial capacity of about 1,250 cc for this cranium (with a reasonable range between approximately 1,200-1,325 cc, depending on how missing portions of the basicranial region are reconstructed). From these determinations, several important implications emerge concerning current interpretations of "tempo and mode" in early hominid brain evolution: 1) already by the early Middle Pleistocene, at least one African hominid species, Homo heidelbergensis, had reached an endocranial capacity within the normal range of modern humans; 2) in spite of its large endocranial capacity, estimates of Bodo's encephalization quotient fall below those found in a large sample of Homo sapiens (both fossil and recent) and Neandertals; and 3) the greatest burst of brain expansion in the Homo lineage may not have been in the last several hundred thousand years, but rather much earlier in the Lower to early Middle Pleistocene.     

更新世中期中国古人类演化区域连续性与多样性的化石证据

以往,在东亚大陆发现的更新世中期人类化石被分别归入直立人和古老型智人。这种分类的主要依据是化石形态特征以及年代。魏敦瑞对周口店第一地点人类化石研究描述的一些头骨、下颌骨和牙齿特征通常被作为判定直立人的标准。根据这些化石的年代分布,一般将30万年前的中更新世晚期作为划分直立人与古老型智人的大致年代界限。近20年来,在非洲、欧洲和东亚新发现了一些更新世中期人类化石,目前古人类学界对中国更新世中期人类化石特征及演化有了与以往不同的认识。最近对大荔、许家窑、盘县大洞、许昌、华龙洞等人类化石的研究显示,近30万年以来东亚大陆人类演化呈现复杂的多样性,将这一时期人类全部归入古老型智人难以准确反映更新世中期中国古人类演化模式及规律。本文结合近年中国更新世中期人类演化研究进展,选择部分具有演化及分类价值的形态特征,分析这些特征在更新世中期中国古人类化石的表现特点。在此基础上,对更新世中期中国古人类演化模式做了尝试性探讨。本研究发现,周口店、和县、沂源、南京等中更新世早期人类化石呈现有较多的区域性特征,形态特征表现相对稳定;而大荔、金牛山、许家窑、许昌、华龙洞、马坝、盘县大洞等中更新世晚期人类在化石形态特征表现复杂多样,变异范围大。此外,在这一时期人类化石上发现较多与生存活动、健康、环境适应有关的证据。根据这些发现,作者认为中国中更新世早期组人类演化以形态连续性为主;进入中更新世晚期,中国古人类演化区域性特征减弱,演化模式以多样性为主。一系列新的化石发现和研究证据提示中更新世晚期东亚大陆可能生存有不同的古人类成员。根据目前掌握的化石形态和年代证据,大约30万年前是中国更新世中期演化变化关键时间节点。     

Brain size and encephalization in early to Mid-Pleistocene Homo

Important changes in the brain have occurred during the course of human evolution. Both absolute and relative size increases can be documented for species of Homo, culminating in the appearance of modern humans. One species that is particularly well-represented by fossil crania is Homo erectus. The mean capacity for 30 individuals is 973 cm(3). Within this group there is substantial variation, but brain size increases slightly in specimens from later time periods. Other Middle Pleistocene crania differ from those of Homo erectus. Characters of the facial skeleton, vault, and cranial base suggest that fossils from sites such as Arago Cave in France, the Sima de los Huesos in Spain, Bodo in Ethiopia, Broken Hill in Zambia, and perhaps Dali in China belong to the taxon Homo heidelbergensis. Ten of these mid-Quaternary hominins have brains averaging 1,206 cm(3) in volume, and many fall beyond the limits of size predicted for Homo erectus of equivalent age. When orbit height is used to construct an index of relative brain size, it is apparent that the (significant) increase in volume documented for the Middle Pleistocene individuals is not simply a consequence of larger body mass. Encephalization quotient values confirm this finding. These changes in absolute and relative brain size can be taken as further corroborative evidence for a speciation event, in which Homo erectus produced a daughter lineage. It is probable that Homo heidelbergensis originated in Africa or western Eurasia and then ranged widely across the Old World. Archaeological traces indicate that these populations differed in their technology and behavior from earlier hominins.     

Reconstructing cranial evolution in an extinct hominin

Homo erectus is the first hominin species with a truly cosmopolitan distribution and resembles recent humans in its broad spatial distribution. The microevolutionary events associated with dispersal and local adaptation may have produced similar population structure in both species. Understanding the evolutionary population dynamics of H. erectus has larger implications for the emergence of later Homo lineages in the Middle Pleistocene. Quantitative genetics models provide a means of interrogating aspects of long-standing H. erectus population history narratives. For the current study, cranial fossils were sorted into six major palaeodemes from sites across Africa and Asia spanning 1.8–0.1 Ma. Three-dimensional shape data from the occipital and frontal bones were used to compare intraspecific variation and test evolutionary hypotheses. Results indicate that H. erectus had higher individual and group variation than Homo sapiens, probably reflecting different levels of genetic diversity and population history in these spatially disperse species. This study also revealed distinct evolutionary histories for frontal and occipital bone shape in H. erectus, with a larger role for natural selection in the former. One scenario consistent with these findings is climate-driven facial adaptation in H. erectus, which is reflected in the frontal bone through integration with the orbits.     

犬齿窝与人类中面部骨骼的演化

犬齿窝是包括现代人类在内的许多人族成员面部骨骼的重要性状,但在分类学上的意义仍存在争议。有学者认为该性状是一个发生于基础面形的近祖性状,除了一些例外,在灭绝和现生的大猿及人属中都存在。另有学者认为,犬齿窝是仅存在于智人及其直系祖先的衍生性状,在发育上与颧齿槽突嵴有关。这种关系并非总是成立,在智人中存在着明显的差异：弧型颧齿槽突嵴和直斜型颧齿槽突嵴与犬齿窝有时共存,有时不共存。我们由此推测,犬齿窝的发生和形态与上颌窦的前部发育有关,颧齿槽突嵴的形态与鼻窦的侧面发育有关。在人类演化的过程中,犬齿窝经历了不同的变形,比如上颌沟(如南方古猿非洲种、傍人粗壮种)、上颌小窝(如傍人粗壮种)、上颌沟(如匠人)或犬齿窝缺如(如傍人埃塞俄比亚种、傍人鲍氏种、肯尼亚扁脸人、人属鲁道夫种)。犬齿窝消失的原因各类群并不相同,如中新世和早更新世人属以及中更新世人属(如人属海德堡种/人属罗得西亚种、人属尼安德特种)。人属罗得西亚种具有弱化的犬齿窝,不具备演化为智人的可能,因此被排除在智人的演化支之外。     

A geometric morphometric analysis of hominin upper first molar shape

Recent studies have revealed interesting differences in upper first molar morphology across the hominin fossil record, particularly significant between H. sapiens and H. neanderthalensis. Usually these analyses have been performed by means of classic morphometric methods, including the measurement of relative cusp areas or the angles defined between cusps. Although these studies have provided valuable information for the morphological characterization of some hominin species, we believe that the analysis of this particular tooth could be more conclusive for taxonomic assignment. In this study, we have applied geometric morphometric methods to explore the morphological variability of the upper first molar (M(1)) across the human fossil record. Our emphasis focuses on the study of the phenetic relationships among the European middle Pleistocene populations (designated as H. heidelbergensis) with H. neanderthalensis and H. sapiens, but the inclusion of Australopithecus and early Homo specimens has helped us to assess the polarity of the observed traits. H. neanderthalensis presents a unique morphology characterized by a relatively distal displacement of the lingual cusps and protrusion in the external outline of a large and bulging hypocone. This morphology can be found in a less pronounced degree in the European early and middle Pleistocene populations, and reaches its maximum expression with the H. neanderthalensis lineage. In contrast, modern humans retain the primitive morphology with a square occlusal polygon associated with a round external outline.