The origin of modern anatomy: By speciation or intraspecific evolution?

Frontal sinus size in South African Later Stone Age Holocene Khoe-San

Frontal size variation is comparatively poorly sampled among sub-Saharan African populations. This study assessed frontal sinus size in a sample of Khoe-San skeletal remains from South African Later Stone Age contexts. Volumes were determined from CT scans of 102 adult crania; individual sex could be estimated in 82 cases. Sinus volume is not sexually dimorphic in this sample. The lack of frontal sinus aplasia is concordant with the low incidences recorded for other sub-Saharan African and most other global populations save those that inhabit high latitudes. There is considerable variation in frontal sinus size among global populations, and the Khoe-San possess among the smallest. The Khoe-San have rather diminutive sinuses compared to sub-Saharan Bantu-speaking populations but resemble a northern African (Sudanese) population. Genetic studies indicate the earliest population divergence within Homo sapiens to have been between the Khoe-San and all other living groups, and that this likely occurred in Africa during the span of Marine Isotope Stages 8-6. There is scant information on frontal sinus development among Late Quaternary African fossils that are likely either closely related or attributable to Homo sapiens. Among these, the MIS 3 cranium from Hofmeyr, South Africa, exhibits distinct Khoe-San cranial affinities and despite its large size has a very small frontal sinus. This raises the possibility that the small frontal sinuses of the Holocene South African Khoe-San might be a feature retained from an earlier MIS 3 population.

Quantifying hominin morphological diversity at the end of the middle Pleistocene: Implications for the origin of Homo sapiens

OBJECTIVES

The Middle Pleistocene (MP) saw the emergence of new species of hominins: Homo sapiens in Africa, H. neanderthalensis, and possibly Denisovans in Eurasia, whose most recent common ancestor is thought to have lived in Africa around 600 ka ago. However, hominin remains from this period present a wide range of morphological variation making it difficult to securely determine their taxonomic attribution and their phylogenetic position within the Homo genus. This study proposes to reconsider the phenetic relationships between MP hominin fossils in order to clarify evolutionary trends and contacts between the populations they represent.

MATERIALS AND METHODS

We used a Geometric Morphometrics approach to quantify the morphological variation of the calvarium of controversial MP specimens from Africa and Eurasia by using a comparative sample that can be divided into 5 groups: H. ergaster, H. erectus, H. neanderthalensis, and H. sapiens, as well as individuals from current modern human populations. We performed a Generalized Procrustes Analysis, a Principal Component Analysis, and Multinomial Principal Component Logistic Regressions to determine the phenetic affinities of the controversial Middle Pleistocene specimens with the other groups.

RESULTS

MP African and Eurasian specimens represent several populations, some of which show strong affinities with H. neanderthalensis in Europe or H. sapiens in Africa, others presenting multiple affinities.

DISCUSSION

These MP populations might have contributed to the emergence of these two species in different proportions. This study proposes a new framework for the human evolutionary history during the MP.

Nasopharyngeal morphology contributes to understanding the "muddle in the middle" of the Pleistocene hominin fossil record

The late archeologist Glynn Isaac first applied the term "muddle in the middle" to a poorly understood period in the Middle Pleistocene human fossil record. This study uses the nasopharyngeal boundaries as a source of traits that may inform this unclear period of human evolution. The nasopharynx lies at the nexus of several vital physiological systems, yet relatively little is known about its importance in human evolution. We analyzed a geographically diverse contemporary Homo sapiens growth series (n = 180 adults, 237 nonadults), Homo neanderthalensis (La Chapelle aux Saints 1, La Ferrassie 1, Forbes Quarry 1, Monte Circeo 1, and Saccopastore 1), mid-Pleistocene Homo (Atapuerca 5, Kabwe 1, Petralona 1, and Steinheim 1), and two Homo erectus sensu lato (KNM-ER 3733 and Sangiran 17). Methods include traditional (Analysis 1) and 3D geometric morphometric analysis (Analysis 2). H. erectus exhibited tall, narrow nasopharyngeal shape, a robust, ancestral morphology. Kabwe 1 and Petralona 1 plotted among H. sapiens in Analysis 2, exhibiting relatively shorter and vertical cartilaginous Eustachian tubes and vertical medial pterygoid plates. Atapuerca 5 and Steinheim 1 exhibited horizontal vomeral orientation similar to H. neanderthalensis, indicating greater relative soft palate length and anteroposterior nasopharynx expansion. They may exhibit synapomorphies with H. neanderthalensis, supporting the accretionary hypothesis. Species-level differences were found among H. sapiens and H. neanderthalensis, including relatively longer dilator tubae muscles and extreme facial airorhynchy among Neanderthals. Furthermore, H. neanderthalensis were autapomorphic in exhibiting horizontal pterygoid plate orientation similar to human infants, suggesting that they may have had inferiorly low placement of the torus tubarius and Eustachian tube orifice on the lateral nasopharyngeal wall in life. This study supports use of osseous nasopharyngeal boundaries both for morphological characters and understanding evolution of otitis media susceptibility in living humans.

An ancestral recombination graph of human, Neanderthal, and Denisovan genomes

Many humans carry genes from Neanderthals, a legacy of past admixture. Existing methods detect this archaic hominin ancestry within human genomes using patterns of linkage disequilibrium or direct comparison to Neanderthal genomes. Each of these methods is limited in sensitivity and scalability. We describe a new ancestral recombination graph inference algorithm that scales to large genome-wide datasets and demonstrate its accuracy on real and simulated data. We then generate a genome-wide ancestral recombination graph including human and archaic hominin genomes. From this, we generate a map within human genomes of archaic ancestry and of genomic regions not shared with archaic hominins either by admixture or incomplete lineage sorting. We find that only 1.5 to 7% of the modern human genome is uniquely human. We also find evidence of multiple bursts of adaptive changes specific to modern humans within the past 600,000 years involving genes related to brain development and function.

Conceptual issues in hominin taxonomy: Homo heidelbergensis and an ethnobiological reframing of species

Efforts to name and classify Middle Pleistocene Homo, often referred to as "Homo heidelbergensis" are hampered by confusing patterns of morphology but also by conflicting paleoanthropological ideologies that are embedded in approaches to hominin taxonomy, nomenclature, and the species concept. We deconstruct these issues to show how the field's search for a "real" species relies on strict adherence to pre-Darwinian essentialist naming rules in a post-typological world. We then examine Middle Pleistocene Homo through the framework of ethnobiology, which examines on how Indigenous societies perceive, classify, and name biological organisms. This research reminds us that across human societies, taxonomies function to (1) identify and classify organisms based on consensus pattern recognition and (2) construct a stable nomenclature for effective storage, retrieval and communication of information. Naming Middle Pleistocene Homo as a "real" species cannot be verified with the current data; and separating regional groups into distinct evolutionary lineages creates taxa that are not defined by readily perceptible or universally salient differences. Based on ethnobiological studies of this kind of patterning, referring to these hominins above the level of the species according to their generic category with modifiers (e.g., "European Middle Pleistocene Homo") is consistent with observed human capabilities for cognitive differentiation, is both necessary and sufficient given the current data, and will allow for the most clear communication across ideologies going forward.

What have the revelations about Neanderthal DNA revealed about Homo sapiens?

Genetic studies have presented increasing indications about the complexity of the interactions between Homo sapiens, Neanderthals and Denisovans, during Pleistocene. The results indicate potential replacement or admixture of the groups of hominins that lived in the same region at different times. Recently, the time of separation among these hominins in relation to the Last Common Ancestor – LCA has been reasonably well established. Events of mixing with emphasis on the Neanderthal gene flow into H. sapiens outside Africa, Denisovans into H. sapiens ancestors in Oceania and continental Asia, Neanderthals into Denisovans, as well as the origin of some phenotypic features in specific populations such as the color of the skin, eyes, hair and predisposition to develop certain kinds of diseases have also been found. The current information supports the existence of both replacement and interbreeding events, and indicates the need to revise the two main explanatory models, the Multiregional and the Out-of-Africa hypotheses, about the origin and evolution of H. sapiens and its co-relatives. There is definitely no longer the possibility of justifying only one model over the other. This paper aims to provide a brief review and update on the debate around this issue, considering the advances brought about by the recent genetic as well as morphological traits analyses.

Identification of African-Specific Admixture between Modern and Archaic Humans

Recent work has demonstrated that two archaic human groups (Neanderthals and Denisovans) interbred with modern humans and contributed to the contemporary human gene pool. These findings relied on the availability of high-coverage genomes from both Neanderthals and Denisovans. Here we search for evidence of archaic admixture from a worldwide panel of 1,667 individuals using an approach that does not require the presence of an archaic human reference genome. We find no evidence for archaic admixture in the Andaman Islands, as previously claimed, or on the island of Flores, where Homo floresiensis fossils have been found. However, we do find evidence for at least one archaic admixture event in sub-Saharan Africa, with the strongest signal in Khoesan and Pygmy individuals from Southern and Central Africa. The locations of these putative archaic admixture tracts are weighted against functional regions of the genome, consistent with the long-term effects of purifying selection against introgressed genetic material.

Deciphering African late middle Pleistocene hominin diversity and the origin of our species

The origin of Homo sapiens remains a matter of debate. The extent and geographic patterning of morphological diversity among Late Middle Pleistocene (LMP) African hominins is largely unknown, thus precluding the definition of boundaries of variability in early H. sapiens and the interpretation of individual fossils. Here we use a phylogenetic modelling method to predict possible morphologies of a last common ancestor of all modern humans, which we compare to LMP African fossils (KNM-ES 11693, Florisbad, Irhoud 1, Omo II, and LH18). Our results support a complex process for the evolution of H. sapiens, with the recognition of different, geographically localised, populations and lineages in Africa - not all of which contributed to our species' origin. Based on the available fossils, H. sapiens appears to have originated from the coalescence of South and, possibly, East-African source populations, while North-African fossils may represent a population which introgressed into Neandertals during the LMP.

Archaic human remains from Hualongdong, China, and Middle Pleistocene human continuity and variation

Middle to Late Pleistocene human evolution in East Asia has remained controversial regarding the extent of morphological continuity through archaic humans and to modern humans. Newly found ∼300,000-y-old human remains from Hualongdong (HLD), China, including a largely complete skull (HLD 6), share East Asian Middle Pleistocene (MPl) human traits of a low vault with a frontal keel (but no parietal sagittal keel or angular torus), a low and wide nasal aperture, a pronounced supraorbital torus (especially medially), a nonlevel nasal floor, and small or absent third molars. It lacks a malar incisure but has a large superior medial pterygoid tubercle. HLD 6 also exhibits a relatively flat superior face, a more vertical mandibular symphysis, a pronounced mental trigone, and simple occlusal morphology, foreshadowing modern human morphology. The HLD human fossils thus variably resemble other later MPl East Asian remains, but add to the overall variation in the sample. Their configurations, with those of other Middle and early Late Pleistocene East Asian remains, support archaic human regional continuity and provide a background to the subsequent archaic-to-modern human transition in the region.

Out of Africa by spontaneous migration waves

Hominin evolution is characterized by progressive regional differentiation, as well as migration waves, leading to anatomically modern humans that are assumed to have emerged in Africa and spread over the whole world. Why or whether Africa was the source region of modern humans and what caused their spread remains subject of ongoing debate. We present a spatially explicit, stochastic numerical model that includes ongoing mutations, demic diffusion, assortative mating and migration waves. Diffusion and assortative mating alone result in a structured population with relatively homogeneous regions bound by sharp clines. The addition of migration waves results in a power-law distribution of wave areas: for every large wave, many more small waves are expected to occur. This suggests that one or more out-of-Africa migrations would probably have been accompanied by numerous smaller migration waves across the world. The migration waves are considered "spontaneous", as the current model excludes environmental or other extrinsic factors. Large waves preferentially emanate from the central areas of large, compact inhabited areas. During the Pleistocene, Africa was the largest such area most of the time, making Africa the statistically most likely origin of anatomically modern humans, without a need to invoke additional environmental or ecological drivers.

Craniometrics Reveal "Two Layers" of Prehistoric Human Dispersal in Eastern Eurasia

This cranio-morphometric study emphasizes a “two-layer model” for eastern Eurasian anatomically modern human (AMH) populations, based on large datasets of 89 population samples including findings directly from ancient archaeological contexts. Results suggest that an initial “first layer” of AMH had related closely to ancestral Andaman, Australian, Papuan, and Jomon groups who likely entered this region via the Southeast Asian landmass, prior to 65–50 kya. A later “second layer” shared strong cranial affinities with Siberians, implying a Northeast Asian source, evidenced by 9 kya in central China and then followed by expansions of descendant groups into Southeast Asia after 4 kya. These two populations shared limited initial exchange, and the second layer grew at a faster rate and in greater numbers, linked with contexts of farming that may have supported increased population densities. Clear dichotomization between the two layers implies a temporally deep divergence of distinct migration routes for AMH through both southern and northern Eurasia.

Tales of Human Migration, Admixture, and Selection in Africa

In the last three decades, genetic studies have played an increasingly important role in exploring human history. They have helped to conclusively establish that anatomically modern humans first appeared in Africa roughly 250,000–350,000 years before present and subsequently migrated to other parts of the world. The history of humans in Africa is complex and includes demographic events that influenced patterns of genetic variation across the continent. Through genetic studies, it has become evident that deep African population history is captured by relationships among African hunter–gatherers, as the world's deepest population divergences occur among these groups, and that the deepest population divergence dates to 300,000 years before present. However, the spread of pastoralism and agriculture in the last few thousand years has shaped the geographic distribution of present-day Africans and their genetic diversity. With today's sequencing technologies, we can obtain full genome sequences from diverse sets of extant and prehistoric Africans. The coming years will contribute exciting new insights toward deciphering human evolutionary history in Africa.

Carriers of mitochondrial DNA macrohaplogroup L3 basal lineages migrated back to Africa from Asia around 70,000 years ago

Background

The main unequivocal conclusion after three decades of phylogeographic mtDNA studies is the African origin of all extant modern humans. In addition, a southern coastal route has been argued for to explain the Eurasian colonization of these African pioneers. Based on the age of macrohaplogroup L3, from which all maternal Eurasian and the majority of African lineages originated, the out-of-Africa event has been dated around 60-70 kya. On the opposite side, we have proposed a northern route through Central Asia across the Levant for that expansion and, consistent with the fossil record, we have dated it around 125 kya. To help bridge differences between the molecular and fossil record ages, in this article we assess the possibility that mtDNA macrohaplogroup L3 matured in Eurasia and returned to Africa as basal L3 lineages around 70 kya.

Results

The coalescence ages of all Eurasian (M,N) and African (L3 ) lineages, both around 71 kya, are not significantly different. The oldest M and N Eurasian clades are found in southeastern Asia instead near of Africa as expected by the southern route hypothesis. The split of the Y-chromosome composite DE haplogroup is very similar to the age of mtDNA L3. An Eurasian origin and back migration to Africa has been proposed for the African Y-chromosome haplogroup E. Inside Africa, frequency distributions of maternal L3 and paternal E lineages are positively correlated. This correlation is not fully explained by geographic or ethnic affinities. This correlation rather seems to be the result of a joint and global replacement of the old autochthonous male and female African lineages by the new Eurasian incomers.

Conclusions

These results are congruent with a model proposing an out-of-Africa migration into Asia, following a northern route, of early anatomically modern humans carrying pre-L3 mtDNA lineages around 125 kya, subsequent diversification of pre-L3 into the basal lineages of L3, a return to Africa of Eurasian fully modern humans around 70 kya carrying the basal L3 lineages and the subsequent diversification of Eurasian-remaining L3 lineages into the M and N lineages in the outside-of-Africa context, and a second Eurasian global expansion by 60 kya, most probably, out of southeast Asia. Climatic conditions and the presence of Neanderthals and other hominins might have played significant roles in these human movements. Moreover, recent studies based on ancient DNA and whole-genome sequencing are also compatible with this hypothesis.

Electronic supplementary material

The online version of this article (10.1186/s12862-018-1211-4) contains supplementary material, which is available to authorized users.

Outstanding questions in the study of archaic hominin admixture

The complete sequencing of archaic and modern human genomes has revolutionized the study of human history and evolution. The application of paleogenomics has answered questions that were beyond the scope of archaeology alone-definitively proving admixture between archaic and modern humans. Despite the remarkable progress made in the study of archaic-modern human admixture, many outstanding questions remain. Here, we review some of these questions, which include how frequent archaic-modern human admixture was in history, to what degree drift and selection are responsible for the loss and retention of introgressed sequences in modern human genomes, and how surviving archaic sequences affect human phenotypes.

A multivariate assessment of the Dali hominin cranium from China: Morphological affinities and implications for Pleistocene evolution in East Asia

OBJECTIVES

A nearly complete hominin fossil cranium from Dali in Shaanxi Province, China was excavated in 1978. We update and expand on previous research by providing a multivariate analysis of the specimen relative to a large sample of Middle and Late Pleistocene hominins.

MATERIALS AND METHODS

We apply principal components analysis, discriminant function analysis, and a method of assessing group membership based on a soft independent model of class analogy (SIMCA) to the study of Dali's cranial morphology. We evaluate Dali's affinities within the context of Middle and Late Pleistocene Homo patterns of craniofacial morphology.

RESULTS

When just the facial skeleton is considered, Dali aligns with Middle Paleolithic H. sapiens and is clearly more derived than African or Eurasian Middle Pleistocene Homo. When just the neurocranium is considered, Dali is most similar to African and Eastern Eurasian but not Western European Middle Pleistocene Homo. When both sets of variables are considered together, Dali exhibits a unique morphology that is most closely aligned with the earliest H. sapiens from North Africa and the Levant.

DISCUSSION

These results add perspective to our previous view of as Dali a "transitional" form between Chinese H. erectus and H. sapiens. Athough no taxonomic allocation is appropriate at this time for Dali, it appears to represent a population that played a more central role in the origin of Chinese H. sapiens. Dali's affinities can be understood in the context of Wu's Continuity with Hybridization scenario and a braided-stream network model of gene flow. Specifically, we propose that Pleistocene populations in China were shaped by periods of isolated evolutionary change within local lineages at certain times, and gene flow between local lineages or between Eastern and Western Eurasia, and Africa at other times, resulting in contributions being made in different capacities to different regions at different times.

New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens

Fossil evidence points to an African origin of Homo sapiens from a group called either H. heidelbergensis or H. rhodesiensis. However, the exact place and time of emergence of H. sapiens remain obscure because the fossil record is scarce and the chronological age of many key specimens remains uncertain. In particular, it is unclear whether the present day 'modern' morphology rapidly emerged approximately 200 thousand years ago (ka) among earlier representatives of H. sapiens or evolved gradually over the last 400 thousand years. Here we report newly discovered human fossils from Jebel Irhoud, Morocco, and interpret the affinities of the hominins from this site with other archaic and recent human groups. We identified a mosaic of features including facial, mandibular and dental morphology that aligns the Jebel Irhoud material with early or recent anatomically modern humans and more primitive neurocranial and endocranial morphology. In combination with an age of 315 ± 34 thousand years (as determined by thermoluminescence dating), this evidence makes Jebel Irhoud the oldest and richest African Middle Stone Age hominin site that documents early stages of the H. sapiens clade in which key features of modern morphology were established. Furthermore, it shows that the evolutionary processes behind the emergence of H. sapiens involved the whole African continent.

OH 83: A new early modern human fossil cranium from the Ndutu beds of Olduvai Gorge, Tanzania

OBJECTIVE

Herein we introduce a newly recovered partial calvaria, OH 83, from the upper Ndutu Beds of Olduvai Gorge, Tanzania. We present the geological context of its discovery and a comparative analysis of its morphology, placing OH 83 within the context of our current understanding of the origins and evolution of Homo sapiens.

MATERIALS AND METHODS

We comparatively assessed the morphology of OH 83 using quantitative and qualitative data from penecontemporaneous fossils and the W.W. Howells modern human craniometric dataset.

RESULTS

OH 83 is geologically dated to ca. 60-32 ka. Its morphology is indicative of an early modern human, falling at the low end of the range of variation for post-orbital cranial breadth, the high end of the range for bifrontal breadth, and near average in frontal length.

DISCUSSION

There have been numerous attempts to use cranial anatomy to define the species Homo sapiens and identify it in the fossil record. These efforts have not met wide agreement by the scientific community due, in part, to the mosaic patterns of cranial variation represented by the fossils. The variable, mosaic pattern of trait expression in the crania of Middle and Late Pleistocene fossils implies that morphological modernity did not occur at once. However, OH 83 demonstrates that by ca. 60-32 ka modern humans in Africa included individuals that are at the fairly small and gracile range of modern human cranial variation.

Homo naledi and Pleistocene hominin evolution in subequatorial Africa

New discoveries and dating of fossil remains from the Rising Star cave system, Cradle of Humankind, South Africa, have strong implications for our understanding of Pleistocene human evolution in Africa. Direct dating of Homo naledi fossils from the Dinaledi Chamber (Berger et al., 2015) shows that they were deposited between about 236 ka and 335 ka (Dirks et al., 2017), placing H. naledi in the later Middle Pleistocene. Hawks and colleagues (Hawks et al., 2017) report the discovery of a second chamber within the Rising Star system (Dirks et al., 2015) that contains H. naledi remains. Previously, only large-brained modern humans or their close relatives had been demonstrated to exist at this late time in Africa, but the fossil evidence for any hominins in subequatorial Africa was very sparse. It is now evident that a diversity of hominin lineages existed in this region, with some divergent lineages contributing DNA to living humans and at least H. naledi representing a survivor from the earliest stages of diversification within Homo. The existence of a diverse array of hominins in subequatorial comports with our present knowledge of diversity across other savanna-adapted species, as well as with palaeoclimate and paleoenvironmental data. H. naledi casts the fossil and archaeological records into a new light, as we cannot exclude that this lineage was responsible for the production of Acheulean or Middle Stone Age tool industries.

Manot 1 calvaria and Recent Modern Human Evolution: an Anthropological Perspective

The time range between 60 ka and 50 ka is one of the most dramatic phases in human biological evolution. In this period, the western part of Eurasia (Europe and the Near East) was populated by Neanderthals, whereas the eastern part (Central Asia and Siberia) was populated by Denisovans. However, by 30 ka, these two populations were replaced by anatomically modern humans (AMH). When did these newcomers arrive and from where? There is accumulating archaeological and genetic evidence suggesting that this demographic shift occurred at the end of MIS 4 [1–3]. Moreover, it is quite clear that a major dispersal of AMH out of Africa was the source of the new populations [4–7]. In this study, we examined specific morphological characteristics of Manot 1 (e.g., suprainiac fossa), and assessed their similarities to the corresponding traits found among Neanderthals. We will show that although the terminology is similar, the traits in each hominin group are of different entities. We also show that Manot 1 and Early Upper Palaeolithic skulls of Europe have many traits in common (e.g., suprainiac fossa, bunning), although Manot 1 is much more gracile. Finally, some of the archaic traits (e.g., suprainiac fossa) seen in Manot 1 can be traced to the Late Pleistocene Aduma skull (~79–105 ka) from Ethiopia or even Eyasi 1 (~200–400 ka) from Tanzania.

Inferences of African evolutionary history from genomic data

Africa is the origin of anatomically modern humans and a continent of linguistic, cultural, environmental, phenotypic, and genetic diversity. However, African populations remain underrepresented in genetic studies, which have largely focused on individuals with European and Asian ancestry. The expansion of high-throughput 'omic' technologies to interrogate multiple tissue types across many biomolecules-DNA, proteins, epigenetic modifications, metabolites, and others-has heralded a new era of investigation into African history. In this review, we summarize how some of these recent advances have been applied to contemporary sub-Saharan African populations to inform studies on human origins and adaptation.

Model-based analyses of whole-genome data reveal a complex evolutionary history involving archaic introgression in Central African Pygmies

Comparisons of whole-genome sequences from ancient and contemporary samples have pointed to several instances of archaic admixture through interbreeding between the ancestors of modern non-Africans and now extinct hominids such as Neanderthals and Denisovans. One implication of these findings is that some adaptive features in contemporary humans may have entered the population via gene flow with archaic forms in Eurasia. Within Africa, fossil evidence suggests that anatomically modern humans (AMH) and various archaic forms coexisted for much of the last 200,000 yr; however, the absence of ancient DNA in Africa has limited our ability to make a direct comparison between archaic and modern human genomes. Here, we use statistical inference based on high coverage whole-genome data (greater than 60×) from contemporary African Pygmy hunter-gatherers as an alternative means to study the evolutionary history of the genus Homo. Using whole-genome simulations that consider demographic histories that include both isolation and gene flow with neighboring farming populations, our inference method rejects the hypothesis that the ancestors of AMH were genetically isolated in Africa, thus providing the first whole genome-level evidence of African archaic admixture. Our inferences also suggest a complex human evolutionary history in Africa, which involves at least a single admixture event from an unknown archaic population into the ancestors of AMH, likely within the last 30,000 yr.

Variability in Early Ahmarian lithic technology and its implications for the model of a Levantine origin of the Protoaurignacian

This paper re-examines lithic technological variability of the Early Ahmarian, one of the early Upper Palaeolithic cultural entities in the Levant, which has often been regarded as a precursor of the Protoaurignacian (the early Upper Palaeolithic in Europe) in arguments for the occurrence of a cultural spread in association with the dispersal of Homo sapiens from the Levant to Europe. Using quantitative data on several lithic techno-typological attributes, we demonstrate that there is a significant degree of variability in the Early Ahmarian between the northern and southern Levant, as previously pointed out by several researchers. In addition, we suggest that the technology similar to the southern Early Ahmarian also existed in the northern Levant, i.e., the Ksar Akil Phase 4 group (the KA 4 group), by introducing new Upper Palaeolithic assemblages from Wadi Kharar 16R, inland Syria. We then review currently available stratigraphic records and radiocarbon dates (including a new date from Wadi Kharar 16R), with special attention to their methodological background. As a result, we propose alternative chronological scenarios, including one that postulates that the southern Early Ahmarian and the KA 4 group appeared later than the northern Early Ahmarian with little or no overlap. On the basis of the alternative scenarios of chronological/geographical patterns of the Early Ahmarian variability, we propose four possible relationships between the Protoaurignacian and the Early Ahmarian, including a new scenario that the appearance of the Protoaurignacian preceded those of similar technological entities in the Levant, i.e., the southern Early Ahmarian and the KA 4 group. If the last hypothesis is substantiated, it requires us to reconsider the model of a Levantine origin of the Protoaurignacian and its palaeoanthropological implications.

Brain, calvarium, cladistics: A new approach to an old question, who are modern humans and Neandertals?

The evolutionary history of the genus Homo is the focus of major research efforts in palaeoanthropology. However, the use of palaeoneurology to infer phylogenies of our genus is rare. Here we use cladistics to test the importance of the brain in differentiating and defining Neandertals and modern humans. The analysis is based on morphological data from the calvarium and endocast of Pleistocene fossils and results in a single most parsimonious cladogram. We demonstrate that the joint use of endocranial and calvarial features with cladistics provides a unique means to understand the evolution of the genus Homo. The main results of this study indicate that: (i) the endocranial features are more phylogenetically informative than the characters from the calvarium; (ii) the specific differentiation of Neandertals and modern humans is mostly supported by well-known calvarial autapomorphies; (iii) the endocranial anatomy of modern humans and Neandertals show strong similarities, which appeared in the fossil record with the last common ancestor of both species; and (iv) apart from encephalisation, human endocranial anatomy changed tremendously during the end of the Middle Pleistocene. This may be linked to major cultural and technological novelties that had happened by the end of the Middle Pleistocene (e.g., expansion of the Middle Stone Age (MSA) in Africa and Mousterian in Europe). The combined study of endocranial and exocranial anatomy offers opportunities to further understand human evolution and the implication for the phylogeny of our genus.

Virtual ancestor reconstruction: Revealing the ancestor of modern humans and Neandertals

The timing and geographic origin of the common ancestor of modern humans and Neandertals remain controversial. A poor Pleistocene hominin fossil record and the evolutionary complexities introduced by dispersals and regionalisation of lineages have fuelled taxonomic uncertainty, while new ancient genomic data have raised completely new questions. Here, we use maximum likelihood and 3D geometric morphometric methods to predict possible morphologies of the last common ancestor of modern humans and Neandertals from a simplified, fully resolved phylogeny. We describe the fully rendered 3D shapes of the predicted ancestors of humans and Neandertals, and assess their similarity to individual fossils or populations of fossils of Pleistocene age. Our results support models of an Afro-European ancestral population in the Middle Pleistocene (Homo heidelbergensis sensu lato) and further predict an African origin for this ancestral population.

The peopling of the African continent and the diaspora into the new world

Africa is the birthplace of anatomically modern humans, and is the geographic origin of human migration across the globe within the last 100,000 years. The history of African populations has consisted of a number of demographic events that have influenced patterns of genetic and phenotypic variation across the continent. With the increasing amount of genomic data and corresponding developments in computational methods, researchers are able to explore long-standing evolutionary questions, expanding our understanding of human history within and outside of Africa. This review will summarize some of the recent findings regarding African demographic history, including the African Diaspora, and will briefly explore their implications for disease susceptibility in populations of African descent.

Early modern humans and morphological variation in Southeast Asia: fossil evidence from Tam Pa Ling, Laos

Little is known about the timing of modern human emergence and occupation in Eastern Eurasia. However a rapid migration out of Africa into Southeast Asia by at least 60 ka is supported by archaeological, paleogenetic and paleoanthropological data. Recent discoveries in Laos, a modern human cranium (TPL1) from Tam Pa Ling‘s cave, provided the first evidence for the presence of early modern humans in mainland Southeast Asia by 63-46 ka. In the current study, a complete human mandible representing a second individual, TPL 2, is described using discrete traits and geometric morphometrics with an emphasis on determining its population affinity. The TPL2 mandible has a chin and other discrete traits consistent with early modern humans, but it retains a robust lateral corpus and internal corporal morphology typical of archaic humans across the Old World. The mosaic morphology of TPL2 and the fully modern human morphology of TPL1 suggest that a large range of morphological variation was present in early modern human populations residing in the eastern Eurasia by MIS 3.

No known hominin species matches the expected dental morphology of the last common ancestor of Neanderthals and modern humans

A central problem in paleoanthropology is the identity of the last common ancestor of Neanderthals and modern humans ([N-MH]LCA). Recently developed analytical techniques now allow this problem to be addressed using a probabilistic morphological framework. This study provides a quantitative reconstruction of the expected dental morphology of the [N-MH]LCA and an assessment of whether known fossil species are compatible with this ancestral position. We show that no known fossil species is a suitable candidate for being the [N-MH]LCA and that all late Early and Middle Pleistocene taxa from Europe have Neanderthal dental affinities, pointing to the existence of a European clade originated around 1 Ma. These results are incongruent with younger molecular divergence estimates and suggest at least one of the following must be true: (i) European fossils and the [N-MH]LCA selectively retained primitive dental traits; (ii) molecular estimates of the divergence between Neanderthals and modern humans are underestimated; or (iii) phenotypic divergence and speciation between both species were decoupled such that phenotypic differentiation, at least in dental morphology, predated speciation.

Facial morphogenesis of the earliest europeans

The modern human face differs from that of our early ancestors in that the facial profile is relatively retracted (orthognathic). This change in facial profile is associated with a characteristic spatial distribution of bone deposition and resorption: growth remodeling. For humans, surface resorption commonly dominates on anteriorly-facing areas of the subnasal region of the maxilla and mandible during development. We mapped the distribution of facial growth remodeling activities on the 900-800 ky maxilla ATD6-69 assigned to H. antecessor, and on the 1.5 My cranium KNM-WT 15000, part of an associated skeleton assigned to African H. erectus. We show that, as in H. sapiens, H. antecessor shows bone resorption over most of the subnasal region. This pattern contrasts with that seen in KNM-WT 15000 where evidence of bone deposition, not resorption, was identified. KNM-WT 15000 is similar to Australopithecus and the extant African apes in this localized area of bone deposition. These new data point to diversity of patterns of facial growth in fossil Homo. The similarities in facial growth in H. antecessor and H. sapiens suggest that one key developmental change responsible for the characteristic facial morphology of modern humans can be traced back at least to H. antecessor.

The great human expansion

Genetic and paleoanthropological evidence is in accord that today's human population is the result of a great demic (demographic and geographic) expansion that began approximately 45,000 to 60,000 y ago in Africa and rapidly resulted in human occupation of almost all of the Earth's habitable regions. Genomic data from contemporary humans suggest that this expansion was accompanied by a continuous loss of genetic diversity, a result of what is called the "serial founder effect." In addition to genomic data, the serial founder effect model is now supported by the genetics of human parasites, morphology, and linguistics. This particular population history gave rise to the two defining features of genetic variation in humans: genomes from the substructured populations of Africa retain an exceptional number of unique variants, and there is a dramatic reduction in genetic diversity within populations living outside of Africa. These two patterns are relevant for medical genetic studies mapping genotypes to phenotypes and for inferring the power of natural selection in human history. It should be appreciated that the initial expansion and subsequent serial founder effect were determined by demographic and sociocultural factors associated with hunter-gatherer populations. How do we reconcile this major demic expansion with the population stability that followed for thousands years until the inventions of agriculture? We review advances in understanding the genetic diversity within Africa and the great human expansion out of Africa and offer hypotheses that can help to establish a more synthetic view of modern 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.