Middle Pleistocene Pongo from Ganxian Cave in southern China with implications for understanding dental size evolution in orangutans.

The Pongo fossil record of China extends from the Early Pleistocene to the Late Pleistocene, but to date, no late Middle Pleistocene samples of Pongo with precise absolute dating have been identified in southern China. Here, we report the recovery of 106 fossil teeth of Pongo from Ganxian Cave in the Bubing Basin, Guangxi, southern China. We dated the speleothems using Uranium-series and dated the two rhinoceros teeth using coupled electron spin resonance/Uranium-series dating methods to between 168.9 ± 2.4 ka and 362 ± 78 ka, respectively. These dates are consistent with the biostratigraphic and magnetostratigraphic age estimates. We further describe the fossil teeth from Ganxian Cave and compare them metrically to samples of fossil Pongo (i.e., Pongo weidenreichi, Pongo duboisi, Pongo palaeosumatrensis, Pongo javensis, and Pongo sp.) from the Early, Middle, and Late Pleistocene and to extant Pongo (i.e., Pongo pygmaeus and Pongo abelii) from Southeast Asia. Based on overall dental size, a high frequency of lingual cingulum remnants on the upper molars, and a low frequency of moderate to heavy wrinkling on the molars, we attribute the Ganxian fossils to P. weidenreichi. Compared with Pongo fossils from other mainland Southeast Asia sites, those from Ganxian confirm that dental size reduction of Pongo occurred principally during the Early and Middle Pleistocene. From the Middle to Late Pleistocene, all teeth except the P3 show little change in occlusal area, indicating that the size of these teeth remained relatively stable over time. The evolutionary trajectory of the Pongo dentition through time may be more complex than previously thought. More orangutan fossils with precise dating constraints are the keys to solving this issue.

Evidence for the latest fossil Pongo in southern China.

Pongo fossils with precise absolute age brackets are rare, limiting our understanding of their taxonomy and spatiotemporal distribution in southern China during the Late Pleistocene. Twenty-four isolated teeth of fossil orangutans were recently discovered during excavations at Yicun Cave in Guangxi Zhuang Autonomous Region, southern China. Here, we dated the fossil-bearing layer using Uranium-series dating of the associated flowstone and soda straw stalactites. Our results date the Yicun orangutan fossils to between 66 ± 0.32 ka and 57 ± 0.26 ka; thus, these fossils currently represent the last appearance datum of Pongo in southern China. We further conducted a detailed morphological comparison of the Yicun fossil teeth with large samples of fossil (n = 2454) and extant (n = 441) orangutans from mainland and island Southeast Asia to determine their taxonomic position. Compared to other fossil and extant orangutan samples, the Yicun Pongo assemblage has larger teeth and displays greater variation in occlusal structure. Based on the high frequency of cingular remnants and light to moderate enamel wrinkling of the molars, we assigned the Yicun fossils to Pongo weidenreichi, a species that was widespread in southern China throughout the Pleistocene. Lastly, we used published stable carbon isotope data of Early to Late Pleistocene mammalian fossil teeth from mainland Southeast Asia to reconstruct changes in the paleoenvironment and to interpret dental size variation of Pongo assemblages in a broader temporal and environmental context. The carbon isotope data show that dental size reduction in Pongo is associated with environmental changes. These morphological changes in Pongo appear to coincide with the expansion of savannah biomes and the contraction of forest habitats from the Middle Pleistocene onward. The variation in dental size of forest-dwelling Pongo in mainland Southeast Asia may have resulted from habitat differentiation during the Pleistocene.

Homo bodoensis and why it matters.

In our original paper, we proposed a new species, Homo bodoensis, to replace the problematical taxa Homo heidelbergensis and Homo rhodesiensis, with the goal of streamlining communication about human evolution in the Chibanian. We received two independent responses. Given their substantial overlap, we provide one combined reply. In this response: (1) we are encouraged that the primary proposal in our paper, to discontinue the use of H. heidelbergensis (as a junior synonym to Homo neanderthalensis) due to its' nomenclatural problems, is acknowledged. (2) we provide additional clarification about the rules governing taxonomic nomenclature as outlined by the International Code of Zoological Nomenclature and join the growing calls for a revision to these rules. (3) we discuss further why H. rhodesiensis should be abandoned, particularly in light of the current sensitivity to using culturally inappropriate names. We conclude that H. bodoensis is a better solution than the proposed alternatives.

Morphometric analysis of the mandibular lingual foramina using cone-beam computed tomography in elderly Korean / Análisis morfométrico de los forámenes linguales mandibulares mediante tomografía computarizada de haz cónico en adultos mayores coreanos

SUMMARY: The aim of this study was to determine the morphologic characteristics of the lingual foramen and lateral lingual foramen using cone-beam CT in elderly Korean. Cone-beam CT images were obtained from 80 Korean older than 50 years (mean age, 65.2 years). The prevalence of the lingual and lateral lingual foramina at the lingual aspect of the mandible was determined. The diameter and height to the upper margin of the foramina from the mandibular inferior margin, and the bone height to the alveolar crest from the mandibular inferior margin were measured. In addition, the location of the lateral lingual foramen, the direction of its canal, and the presence of communication with the mandibular canal were evaluated. All of elderly Korean possessed at least one lingual foramen, with two or three foramina occurring in 77.5 % of Korean. A lateral lingual foramen was observed in 91.3 % of Korean, with the prevalence being highest at the second premolar in dentulous cases (21.6 %; 33/153). The very high frequencies of these foramina were attributable to high frequencies of relatively small-diameter inferior lingual foramen and lateral lingual foramen in the incisor region. The prevalence of a large-diameter (≥1 mm) superior lingual foramen was high, at 31.0 %. A large-diameter lateral lingual foramen in the premolar region occurred at a frequency of 17.0 %; communication with the mandibular canal was observed in 70.0 % of these cases. These quantitative data on the lingual and lateral lingual foramina of the mandible provide valuable information that could help to avoid surgical complications during implant placement in elderly Korean.

RESUMEN: El objetivo de este estudio fue determinar las características morfológicas del foramen lingual y del foramen lingual lateral mediante TC de haz cónico en adultos mayores coreanos. Se obtuvieron imágenes de TC de haz cónico de 80 coreanos mayores de 50 años (edad media, 65,2 años). Se determinó la prevalencia de los forámenes linguales y linguales laterales en la cara lingual de la mandíbula. Se midió el diámetro y la altura hasta el margen superior de los forámenes desde el margen inferior mandibular, y la altura ósea hasta la cresta alveolar desde el margen inferior mandibular. Además, se evaluó la ubicación del foramen lingual lateral, la dirección de su canal y la presencia de comunicación con el canal mandibular. Todos los adultos mayores coreanos tenían al menos un foramen lingual, con dos o tres forámenes en el 77,5 %. Se observó un foramen lingual lateral en el 91,3 %, siendo la prevalencia más alta en el segundo premolar en casos dentados (21,6 %; 33/ 153). Las mayores frecuencias de estos forámenes se atribuyeron a altas frecuencias de foramen lingual inferior y foramen lingual lateral de diámetro relativamente pequeño en la región de los incisivos. La prevalencia de un foramen lingual superior de gran diámetro (≥1 mm) fue alta, del 31,0 %. Un foramen lingual lateral de gran diámetro en la región premolar ocurrió con una frecuencia del 17,0 %; se observó comunicación con el canal mandibular en el 70,0 % de estos casos. Estos datos cuantitativos sobre los forámenes linguales y linguales laterales de la mandíbula proporcionan información valiosa que podría ayudar a evitar complicaciones quirúrgicas durante la colocación de implantes en adultos mayores coreanos.

Evolution of cranial capacity revisited: A view from the late Middle Pleistocene cranium from Xujiayao, China.

The Late Middle Pleistocene hominin fossils from the Xujiayao site in northern China have been closely studied in light of their morphological variability. However, all previous studies have focused on separated cranial fragments. Here, we report the first reconstruction of a fairly complete posterior cranium, Xujiayao 6 (XJY 6), confidently dated to ∼200-160 ka, which facilitated an assessment of its overall cranial size. XJY 6 was reconstructed from three of the original fragments-the PA1486 (No.7/XJY 6a) occipital bone, PA1490 (No.10/XJY 6b) right parietal bone, and PA1498 (No.17/XJY 15) left temporal bone-which originated from the same young adult individual. The XJY 6 endocranial capacity, estimated by measuring endocranial volume, was estimated using multiple regression formulae derived from ectocranial and endocranial measurements on select samples of Pleistocene hominins and recent modern humans. The results indicate that the larger pooled sample of both Pleistocene and recent modern humans was more robust for the endocranial capacity estimate. Based on the pooled sample using the ectocranial and endocranial measurements, we conservatively estimate the XJY 6 endocranial volume to be ∼1700 cm3 with a 95% confidence interval of 1555-1781 cm3. This is close to Xuchang 1, which dates to 125-105 ka and whose endocranial volume is ∼1800 cm3. Thus, XJY 6 provides the earliest evidence of a brain size that falls in the upper range of Neanderthals and modern Homo sapiens. XJY 6, together with Xuchang 1, Homo floresiensis, Homo luzonensis, and Homo naledi, challenge the general pattern that brain size gradually increases over geological time. This study also finds that hominin brain size expansion occurred at different rates across time and space.

Resolving the "muddle in the middle": The case for Homo bodoensis sp. nov.

Recent developments in the field of palaeoanthropology necessitate the suppression of two hominin taxa and the introduction of a new species of hominins to help resolve the current nebulous state of Middle Pleistocene (Chibanian) hominin taxonomy. In particular, the poorly defined and variably understood hominin taxa Homo heidelbergensis (both sensu stricto and sensu lato) and Homo rhodesiensis need to be abandoned as they fail to reflect the full range of hominin variability in the Middle Pleistocene. Instead, we propose: (1) introduction of a new taxon, Homo bodoensis sp. nov., as an early Middle Pleistocene ancestor of the Homo sapiens lineage, with a pan-African distribution that extends into the eastern Mediterranean (Southeast Europe and the Levant); (2) that many of the fossils from Western Europe (e.g. Sima de los Huesos) currently assigned to H. heidelbergensis s.s. be reassigned to Homo neanderthalensis to reflect the early appearance of Neanderthal derived traits in the Middle Pleistocene in the region; and (3) that the Middle Pleistocene Asian fossils, particularly from China, likely represent a different lineage altogether.

Morphology of the temporalis muscle focusing on the tendinous attachment onto the coronoid process.

The temporalis muscle is usually described as a single layer originating at the temporal line, converging to a tendon, and inserting onto a narrow site of the coronoid process. However, recent studies have shown that the temporalis muscle can be divided into two or three separate segments and the distal attachment continues inferiorly beyond the coronoid process. Therefore, the aims of this study were to analyze the morphology of the temporalis muscle focusing on the tendinous attachment onto the coronoid process and to provide educational values. The temporalis muscle was carefully dissected in 26 cadavers and classified based on the muscle fascicle direction. Each divided part was sketched and measured based on bony landmarks to elucidate its tendinous insertion site onto the coronoid process, and the results obtained were reviewed through the literature. The temporalis muscle ends at two distinct terminal tendons with wider insertion sites than usually presented in textbooks and atlases and separates into two parts that combine to act as a single structural unit. The superficial part is a large fan-shaped muscle commonly recognized as the temporalis muscle. This converges infero-medially to form the superficial tendon and the lateral boundary of the retromolar triangle. Meanwhile, the deep part is a narrow vertically oriented rectangular muscle that converges postero-laterally to form the deep tendon and the medial boundary of the retromolar triangle. These results indicate that understanding the temporalis muscle's insertion site onto the coronoid process will be useful clinically with educational values during surgical procedures.

26Al/10Be Burial Dating of the Middle Pleistocene Yiyuan Hominin Fossil Site, Shandong Province, Northern China.

The Yiyuan hominin fossil site is one of the few localities in China where a partial skullcap and several loose teeth of Homo erectus have been discovered. Yiyuan was previously assigned broadly to the Middle Pleistocene by biostratigraphical correlation and ESR/U-series dating. Here, we report the first application of a radio-isotopic dating method to the site. 26Al/10Be burial dating results derived from two sand samples from the fossiliferous deposits show that the hominin fossils can be confidently dated to 0.64 ± 0.08 Ma (million years ago). The reliability of this age is supported by the zero age of modern fluvial sediment near the cave. Our result is consistent with the age estimation based on biostratigraphic correlation and supports the argument that the Yiyuan and Zhoukoudian Locality 1 H. erectus fossils are contemporaneous. The results presented here, along with other recent chronological studies on Chinese Middle Pleistocene hominin sites, indicate that the time span from 600-400 ka (thousand years ago) is a critical period for human evolution in East Asia. Importantly, this time bracket includes several major climatic changes that would have influenced hominins, both morphologically and behaviorally.

Influences of Sedimentary Environments and Volcanic Sources on Diagenetic Alteration of Volcanic Tuffs in South China.

Permian-Triassic (P-Tr) altered volcanic ashes (tuffs) are widely distributed within the P-Tr boundary successions in South China. Volcanic altered ashes from terrestrial section-Chahe (CH) and marine section-Shangsi (SS) are selected to further understand the influence of sedimentary environments and volcanic sources on diagenetic alterarion on volcanic tuffs. The zircon 206Pb/238U ages of the corresponding beds between two sections are almost synchronous. Sedimentary environment of the altered tuffs was characterized by a low pH and did not experience a hydrothermal process. The dominant clay minerals of all the tuff beds are illite-smectite (I-S) minerals, with minor chlorite and kaolinite. I-S minerals of CH (R3) are more ordered than SS (R1), suggesting that CH also shows a higher diagenetic grade and more intensive chemical weathering. Besides, the nature of the volcanism of the tuff beds studied is derived from different magma sources. The clay mineral compositions of tuffs have little relation with the types of source volcanism and the depositional environments. Instead, the degree of the mixed-layer clay minerals and the REE distribution are mainly dependent upon the sedimentary environments. Thus, the mixed-layer clay minerals ratio and their geochemical index can be used as the paleoenvironmental indicator.

Re-dating Zhoukoudian Upper Cave, northern China and its regional significance.

Due to the presence of multiple partial modern human skeletons thought to have been interred along with a diversity of evidence of symbolic behavior, Zhoukoudian Upper Cave (ZKD UC; formally "Choukoutien") from northern China has long been a critical site for understanding Late Quaternary human evolution and particularly the role eastern Asia played. Unfortunately, uncertainty regarding ZKD UC's chronology has long hindered determination of its importance in the debate over modern human origins. This situation has been particularly problematic because dates from the primary archaeological layers of ZKD UC have ranged from the Late Pleistocene to the Early Holocene (∼34-10 ka), with clearly different implications depending on which age is used. Here, we present a new set of accelerator mass spectrometry radiocarbon dating results from ZKD UC. Based on this new set of dates and further re-evaluations of the previous dating analyses, archaeological materials, published excavation reports and stratigraphy, we conclude that the ZKD UC archaeological layers minimally date to 35.1-33.5 ka. Given the similarities between the human fossils and archaeology between ZKD UC and western Eurasia, it is likely that the ZKD UC human foragers were part of dispersal events across northern Eurasia toward Siberia and eventually reaching into northern China.

On the origin of modern humans: Asian perspectives.

The traditional "out of Africa" model, which posits a dispersal of modern Homo sapiens across Eurasia as a single wave at ~60,000 years ago and the subsequent replacement of all indigenous populations, is in need of revision. Recent discoveries from archaeology, hominin paleontology, geochronology, genetics, and paleoenvironmental studies have contributed to a better understanding of the Late Pleistocene record in Asia. Important findings highlighted here include growing evidence for multiple dispersals predating 60,000 years ago in regions such as southern and eastern Asia. Modern humans moving into Asia met Neandertals, Denisovans, mid-Pleistocene Homo, and possibly H. floresiensis, with some degree of interbreeding occurring. These early human dispersals, which left at least some genetic traces in modern populations, indicate that later replacements were not wholesale.

Metric and geometric morphometric analysis of new hominin fossils from Maba (Guangdong, China).

We present an analysis of a set of previously unreported hominin fossils from Maba (Guangdong, China), a cave site that is best known for the presence of a partial hominin cranium currently assigned as mid-Pleistocene Homo and that has been traditionally dated to around the Middle-Late Pleistocene transition. A more recent set of Uranium series dates indicate that the Maba travertine may date to >237 ka (thousands of years ago), as opposed to the original U-series date, which placed Maba at 135-129 ka. The fossils under study include five upper first and second molars and a partial left mandible with a socketed m3, all recovered from different parts of the site than the cranium or the dated sediments. The results of our metric and 2D geometric morphometric ('GM') study suggest that the upper first molars are likely from modern humans, suggesting a more recent origin. The upper second molars align more closely with modern humans, though the minimum spanning tree from the 2D GM analysis also connects Maba to Homo neanderthalensis. The patterning in the M2s is not as clear as with the M1s. The m3 and partial mandible are morphometrically intermediate between Holocene modern humans and older Homo sapiens. However, a minimum spanning tree indicates that both the partial mandible and m3 align most closely with Holocene modern humans, and they also may be substantially younger than the cranium. Because questions exist regarding the context and the relationship of the dated travertine with the hominin fossils, we suggest caution is warranted in interpreting the Maba specimens.

Middle Pleistocene bifaces from Fengshudao (Bose Basin, Guangxi, China).

The Bose (also Baise) Basin in Guangxi, southern China is well known for the presence of Paleolithic bifacially worked implements. The Bose Basin handaxes came to the attention of the international scientific community primarily for two reasons: 1) the age at 803 ka (thousands of years), places it at the Early to Middle Pleistocene transition; and 2) the presence of bifaces tests the validity of the Movius Line and whether it was time to simply discard the model. However, questions were almost immediately raised because the age was based on the supposed association of Australasian tektites that may or may not have been redeposited, and at the time of the initial publications all of the Bose Basin handaxes were surface collected. Thus, whether the Bose bifaces can necessarily be associated with the tektites and whether the tektites themselves were redeposited are important considerations. Here, we report the findings from recent excavations from the Fengshudao site located in the Bose Basin. The primary findings are: 1) the in situ excavation of tektites, which do not appear to have been redeposited, in association with bifaces from one stratigraphic level from one site indicates that the age of these stone tools should be around 803 ka; 2) the Fengshudao hominins were utilizing locally-available quartz, quartzite, and sandstone river cobbles; and 3) in a number of aspects, the Fengshudao handaxe morphology differs from the typical western Acheulean, and are quite large and thick compared with even the bifaces from other regions of eastern Asia (e.g., Luonan Basin, China; Imjin/Hantan River Basins, Korea). Although Fengshudao may be a case of western Acheulean hominins dispersing into the Bose Basin from nearby South Asia, it is quite possible that the Fengshudao bifaces can be considered an example of convergent evolution.

Comparison of handaxes from Bose Basin (China) and the western Acheulean indicates convergence of form, not cognitive differences.

Alleged differences between Palaeolithic assemblages from eastern Asia and the west have been the focus of controversial discussion for over half a century, most famously in terms of the so-called 'Movius Line'. Recent discussion has centered on issues of comparability between handaxes from eastern Asian and 'Acheulean' examples from western portions of the Old World. Here, we present a multivariate morphometric analysis in order to more fully document how Mid-Pleistocene (i.e. ∼803 Kyr) handaxes from Bose Basin, China compare to examples from the west, as well as with additional (Mode 1) cores from across the Old World. Results show that handaxes from both the western Old World and Bose are significantly different from the Mode 1 cores, suggesting a gross comparability with regard to functionally-related form. Results also demonstrate overlap between the ranges of shape variation in Acheulean handaxes and those from Bose, demonstrating that neither raw material nor cognitive factors were an absolute impediment to Bose hominins in making comparable handaxe forms to their hominin kin west of the Movius Line. However, the shapes of western handaxes are different from the Bose examples to a statistically significant degree. Moreover, the handaxe assemblages from the western Old World are all more similar to each other than any individual assemblage is to the Bose handaxes. Variation in handaxe form is also comparatively high for the Bose material, consistent with suggestions that they represent an emergent, convergent instance of handaxe technology authored by Pleistocene hominins with cognitive capacities directly comparable to those of 'Acheulean' hominins.