Dating of the Lower Pleistocene Vertebrate Site of Tsiotra Vryssi (Mygdonia Basin, Greece): Biochronology, Magnetostratigraphy, and Cosmogenic Radionuclides

Background and scope: The late Villafranchian large mammal age (~2.0–1.2 Ma) of the Early Pleistocene is a crucial interval of time for mammal/hominin migrations and faunal turnovers in western Eurasia. However, an accurate chronological framework for the Balkans and adjacent territories is still missing, preventing pan-European biogeographic correlations and schemes. In this article, we report the first detailed chronological scheme for the late Villafranchian of southeastern Europe through a comprehensive and multidisciplinary dating approach (biochronology, magnetostratigraphy, and cosmogenic radionuclides) of the recently discovered Lower Pleistocene vertebrate site Tsiotra Vryssi (TSR) in the Mygdonia Basin, Greece. Results: The minimum burial ages (1.88 ± 0.16 Ma, 2.10 ± 0.18 Ma, and 1.98 ± 0.18 Ma) provided by the method of cosmogenic radionuclides indicate that the normal magnetic polarity identified below the fossiliferous layer correlates to the Olduvai subchron (1.95–1.78 Ma; C2n). Therefore, an age younger than 1.78 Ma is indicated for the fossiliferous layer, which was deposited during reverse polarity chron C1r. These results are in agreement with the biochronological data, which further point to an upper age limit at ~1.5 Ma. Overall, an age between 1.78 and ~1.5 Ma (i.e., within the first part of the late Villafranchian) is proposed for the TSR fauna. Conclusions: Our results not only provide age constraints for the local mammal faunal succession, thus allowing for a better understanding of faunal changes within the same sedimentary basin, but also contribute to improving correlations on a broader scale, leading to more accurate biogeographic, palaeoecological, and taphonomic interpretations.

The Palaeolithic cave of Kalamakia (Mani Peninsula), Greece: new insights on the palaeoenvironment using microvertebrates and mesowear analysis of ruminant teeth

In the present study, results from the examination of mammalian teeth from the cave of Kalamakia with modern techniques, as well as a qualitative overview of the microvertebrate and lithic material, are presented together with a revision of previous related work done for the site, in order to assess the palaeoenvironmental conditions in the area and the role they played in the Neanderthal's repeated occupation of the cave. Geometric morphometrics analyses performed on the first lower molars of Microtus spp. individuals revealed persistent populations of the subgenus Terricola, in which the presence of Microtus thomasi and Microtus subterraneus are continuous through the stratigraphic units. Mesowear analyses performed on ruminant teeth showed no significant variation in toothwear through time, except for relatively elevated levels of dietary abrasion for the more recent samples. The study of the lithics revealed that Neanderthals visited the cave in alternating short and more permanent episodes of occupation, with the human occupants exhibiting special concern for raw material economy, while exploiting poor raw materials for the construction of their tools. The overview of the microvertebrate remains showed a growing trend towards the upper stratigraphic units, where taxa typical of temperate climate, open woodland and shrubland become more dominant. These results, along with observations derived from previous studies, suggest that temperate climate and open environment were the factors that mainly contributed to making the cave of Kalamakia attractive as a habitation site to the humans of the area.

Virtual Reconstruction and Comparative Analyses of the Middle Pleistocene Apidima 2 Cranium (Greece)

The Apidima 2 fossil cranium from South Peloponnese is one of the most important hominin specimens from Southeast Europe. Nevertheless, there has been continuous controversy as to whether it represents a so-called Preneandertal/Homo heidelbergensis such as, for example, the Petralona cranium from Northern Greece or a more derived Neandertal. Recent absolute dating evidence alone cannot clarify the issue because both classifications would be possible during the respective Middle Pleistocene time span. Since only limited data were available on the cranium, there have been repeated claims for the need of a broader comparative study of the hominin. The present article presents a CT-based virtual reconstruction including corrections of postmortem fractures and deformation as well as detailed metrical and morphological analyses of the specimen. Endocranial capacity could be estimated for the first time based on virtual reconstruction. Our multivariate analyses of metric data from the face and vault revealed close affinities to early and later Neandertals, especially showing the derived facial morphometrics. In addition, comparative analyses of Apidima 2 were done for many derived Neandertal features. Here again, a significant number of Neandertal features could be found in the Apidima cranium but no conditions common in Preneandertals. In agreement with a later Middle Pleistocene age Apidima is currently the earliest evidence of a hominin in Europe with such a derived Neandertal facial morphology. The place of Apidima in the complex process of Neandertal evolution as well as its taxonomic classification are discussed as well. Anat Rec, 303:1374-1392, 2020. © 2019 American Association for Anatomy.

Evaluating developmental shape changes in Homo antecessor subadult facial morphology

The fossil ATD6-69 from Atapuerca, Spain, dated to ca. 900 ka (thousands of years ago) has been suggested to mark the earliest appearance of modern human facial features. However, this specimen is a subadult and the interpretation of its morphology remains controversial, because it is unclear how developmental shape changes would affect the features that link ATD6-69 to modern humans. Here we analyze ATD6-69 in an evolutionary and developmental context. Our modern human sample comprises cross-sectional growth series from four populations. The fossil sample covers human specimens from the Pleistocene to the Upper Paleolithic, and includes several subadult Early Pleistocene humans and Neanderthals. We digitized landmarks and semilandmarks on surface and CT scans and analyzed the Procrustes shape coordinates using multivariate statistics. Ontogenetic allometric trajectories and developmental simulations were employed in order to identify growth patterns and to visualize potential adult shapes of ATD6-69. We show that facial differences between modern and archaic humans are not exclusively allometric. We find that while postnatal growth further accentuates the differences in facial features between Neanderthals and modern humans, those features that have been suggested to link ATD6-69's morphology to modern humans would not have been significantly altered in the course of subsequent development. In particular, the infraorbital depression on this specimen would have persisted into adulthood. However, many of the facial features that ATD6-69 shares with modern humans can be considered to be part of a generalized pattern of facial architecture. Our results present a complex picture regarding the polarity of facial features and demonstrate that some modern human-like facial morphology is intermittently present in Middle Pleistocene humans. We suggest that some of the facial features that characterize recent modern humans may have developed multiple times in human evolution.

Middle Pleistocene human facial morphology in an evolutionary and developmental context

Neanderthals and modern humans exhibit distinct facial architectures. The patterning of facial morphology of their predecessors, the Middle Pleistocene humans, is more mosaic showing a mix of archaic and modern morphologies. Significant changes in facial size and robusticity occurred throughout Pleistocene human evolution, resulting in temporal trends in both facial reduction and enlargement. However, the allometric patterning in facial morphology in archaic humans is not well understood. This study explores temporal trends in facial morphology in order to gain a clearer understanding of the polarity of features, and describes the allometric patterning of facial shape. The modern human sample comprises cross-sectional growth series of four morphologically distinct human populations. The fossil sample covers specimens from the Middle Pleistocene to the Upper Paleolithic. We digitized landmarks and semilandmarks on surface and computed tomography scans and analyzed the Procrustes shape coordinates. Principal component analyses were performed, and Procrustes distances were used to identify phenetic similarities between fossil hominins. In order to explore the influence of size on facial features, allometric trajectories were calculated for fossil and modern human groups, and developmental simulations were performed. We show that facial features can be used to separate Pleistocene humans into temporal clusters. The distinctly modern human pattern of facial morphology is already present around 170 ka. Species- and population-specific facial features develop before two years of age, and several of the large-scale facial differences between Neanderthals and Middle Pleistocene humans are due to scaling along a shared allometric trajectory. These features include aspects of the frontal bone, browridge morphology, nasal aperture size and facial prognathism. Infraorbital surface topography and orientation of the midface in the European Middle Pleistocene hominins is intermediate between the African Middle Pleistocene and Neanderthal condition. This could suggest that the European Middle Pleistocene hominins display incipient Neanderthal features.