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The oral microbiome plays key roles in human biology, health, and disease, but little is known about the global diversity, variation, or evolution of this microbial community. To better understand the evolution and changing ecology of the human oral microbiome, we analyzed 124 dental biofilm metagenomes from humans, including Neanderthals and Late Pleistocene to present-day modern humans, chimpanzees, and gorillas, as well as New World howler monkeys for comparison. We find that a core microbiome of primarily biofilm structural taxa has been maintained throughout African hominid evolution, and these microbial groups are also shared with howler monkeys, suggesting that they have been important oral members since before the catarrhine-platyrrhine split ca. 40 Mya. However, community structure and individual microbial phylogenies do not closely reflect host relationships, and the dental biofilms of Homo and chimpanzees are distinguished by major taxonomic and functional differences. Reconstructing oral metagenomes from up to 100 thousand years ago, we show that the microbial profiles of both Neanderthals and modern humans are highly similar, sharing functional adaptations in nutrient metabolism. These include an apparent Homo -specific acquisition of salivary amylase-binding capability by oral streptococci, suggesting microbial coadaptation with host diet. We additionally find evidence of shared genetic diversity in the oral bacteria of Neanderthal and Upper Paleolithic modern humans that is not observed in later modern human populations. Differences in the oral microbiomes of African hominids provide insights into human evolution, the ancestral state of the human microbiome, and a temporal framework for understanding microbial health and disease., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

Background: The molecular out of Africa hypothesis, OOAH, has been considered as an established fact amid population geneticists for some 25-30 years despite the early concern with it among phylogeneticists with experience beyond that of Homo. The palaeontological support for the hypothesis is also questionable, a circumstance that in the light of expanding Eurasian palaeontological knowledge has become accentuated through the last decades., Results: The direction of evolution in the phylogenetic tree of modern humans (Homo sapiens sapiens, Hss) was established inter alia by applying progressive phylogenetic analysis to an mtDNA sampling that included a Eurasian, Lund, and the African Mbuti, San and Yoruba. The examination identified the African populations as paraphyletic, thereby compromising the OOAH. The finding, which was consistent with the out of Eurasia hypothesis, OOEH, was corroborated by the mtDNA introgression from Hss into Hsnn (Neanderthals) that demonstrated the temporal and physical Eurasian coexistence of the two lineages. The results are consistent with the palaeontologically established presence of H. erectus in Eurasia, a Eurasian divergence between H. sapiens and H. antecessor ≈ 850,000 YBP, an Hs divergence between Hss and Hsn (Neanderthals + Denisovans) ≈ 800,000 YBP, an mtDNA introgression from Hss into Hsnn* ≈ 500,000 YBP and an Eurasian divergence among the ancestors of extant Hss ≈ 250,000 YBP at the exodus of Mbuti/San into Africa., Conclusions: The present study showed that Eurasia was not the receiver but the donor in Hss evolution. The findings that Homo left Africa as erectus and returned as sapiens sapiens constitute a change in the understanding of Hs evolution to one that conforms to the extensive Eurasian record of Hs palaeontology and archaeology.

We challenge the view that our species, Homo sapiens, evolved within a single population and/or region of Africa. The chronology and physical diversity of Pleistocene human fossils suggest that morphologically varied populations pertaining to the H. sapiens clade lived throughout Africa. Similarly, the African archaeological record demonstrates the polycentric origin and persistence of regionally distinct Pleistocene material culture in a variety of paleoecological settings. Genetic studies also indicate that present-day population structure within Africa extends to deep times, paralleling a paleoenvironmental record of shifting and fractured habitable zones. We argue that these fields support an emerging view of a highly structured African prehistory that should be considered in human evolutionary inferences, prompting new interpretations, questions, and interdisciplinary research directions., (Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Humans are ecosystems containing trillions of microorganisms, but the evolutionary history of this microbiome is obscured by a lack of knowledge about microbiomes of African apes. We sequenced the gut communities of hundreds of chimpanzees, bonobos, and gorillas and developed a phylogenetic approach to reconstruct how present-day human microbiomes have diverged from those of ancestral populations. Compositional change in the microbiome was slow and clock-like during African ape diversification, but human microbiomes have deviated from the ancestral state at an accelerated rate. Relative to the microbiomes of wild apes, human microbiomes have lost ancestral microbial diversity while becoming specialized for animal-based diets. Individual wild apes cultivate more phyla, classes, orders, families, genera, and species of bacteria than do individual humans across a range of societies. These results indicate that humanity has experienced a depletion of the gut flora since diverging from Pan.

Today, gorillas and chimpanzees live in tropical forests, where acid soils do not favor fossilization. It is thus widely believed that there are no fossils of chimpanzees or gorillas. However, four teeth of a 0.5-million-year (Ma)-old chimpanzee were discovered in the rift valley of Kenya (McBrearty and Jablonski, 2005), and a handful of teeth of a 10-Ma-old gorilla-like creature were found in Ethiopia (Suwa et al., 2007), close to the major sites of Homo discoveries. These discoveries indicate that chimpanzees and gorillas once shared their range with early Homo. However, the thousands of hominin fossils discovered in the past century have all been attributed to the Homo line. Thus far, our family tree looks like a bush with many dead-branches. If one admits the possibility that the australopithecines can also be the ancestors of African great apes, one can place Paranthropus on the side of gorilla ancestors and divide the remaining Australopithecus based on the brain size into the two main lines of humans and chimpanzees, thereby resulting in a coherent family tree., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

Most great ape genetic variation remains uncharacterized; however, its study is critical for understanding population history, recombination, selection and susceptibility to disease. Here we sequence to high coverage a total of 79 wild- and captive-born individuals representing all six great ape species and seven subspecies and report 88.8 million single nucleotide polymorphisms. Our analysis provides support for genetically distinct populations within each species, signals of gene flow, and the split of common chimpanzees into two distinct groups: Nigeria-Cameroon/western and central/eastern populations. We find extensive inbreeding in almost all wild populations, with eastern gorillas being the most extreme. Inferred effective population sizes have varied radically over time in different lineages and this appears to have a profound effect on the genetic diversity at, or close to, genes in almost all species. We discover and assign 1,982 loss-of-function variants throughout the human and great ape lineages, determining that the rate of gene loss has not been different in the human branch compared to other internal branches in the great ape phylogeny. This comprehensive catalogue of great ape genome diversity provides a framework for understanding evolution and a resource for more effective management of wild and captive great ape populations.

Currently restricted to Southeast Asia and Africa, extant hominoids are the remnants of a group that was much more diverse during the Miocene. Apes initially diversified in Africa during the early Miocene, but by the middle Miocene they extended their geographical range into Eurasia, where they experienced an impressive evolutionary radiation. Understanding the role of Eurasian hominoids in the origin and evolution of the great-ape-and-human clade (Hominidae) is partly hampered by phylogenetic uncertainties, the scarcity and incompleteness of fossil remains, the current restricted diversity of the group, and pervasive homoplasy. Nevertheless, scientific knowledge of the Eurasian hominoid radiation has significantly improved during the last decade. In the case of Western Europe, this has been due to the discovery of new remains from the Vallès-Penedès Basin (Catalonia, Spain). Here, I review the fossil record of Vallès-Penedès apes and consider its implications. Although significant disagreements persist among scholars, some important lessons can be learned regarding the evolutionary history of the closest living relatives of humans., (Copyright © 2012 Wiley Periodicals, Inc.)

Reconstructing the origin and early evolutionary history of anthropoid primates (monkeys, apes, and humans) is a current focus of paleoprimatology. Although earlier hypotheses frequently supported an African origin for anthropoids, recent discoveries of older and phylogenetically more basal fossils in China and Myanmar indicate that the group originated in Asia. Given the Oligocene-Recent history of African anthropoids, the colonization of Africa by early anthropoids hailing from Asia was a decisive event in primate evolution. However, the fossil record has so far failed to constrain the nature and timing of this pivotal event. Here we describe a fossil primate from the late middle Eocene Pondaung Formation of Myanmar, Afrasia djijidae gen. et sp. nov., that is remarkably similar to, yet dentally more primitive than, the roughly contemporaneous North African anthropoid Afrotarsius. Phylogenetic analysis suggests that Afrasia and Afrotarsius are sister taxa within a basal anthropoid clade designated as the infraorder Eosimiiformes. Current knowledge of eosimiiform relationships and their distribution through space and time suggests that members of this clade dispersed from Asia to Africa sometime during the middle Eocene, shortly before their first appearance in the African fossil record. Crown anthropoids and their nearest fossil relatives do not appear to be specially related to Afrotarsius, suggesting one or more additional episodes of dispersal from Asia to Africa. Hystricognathous rodents, anthracotheres, and possibly other Asian mammal groups seem to have colonized Africa at roughly the same time or shortly after anthropoids gained their first toehold there.

The classification and phylogenetic relationships of the middle Pleistocene human fossil record remains one of the most intractable problems in paleoanthropology. Several authors have noted broad resemblances between European and African fossils from this period, suggesting a single taxon ancestral to both modern humans and Neanderthals. Others point out 'incipient' Neanderthal features in the morphology of the European sample and have argued for their inclusion in the Neanderthal lineage exclusively, following a model of accretionary evolution of Neanderthals. We approach these questions using geometric morphometric methods which allow the intuitive visualization and quantification of features previously described qualitatively. We apply these techniques to evaluate proposed cranio-facial 'incipient' facial, vault, and basicranial traits in a middle-late Pleistocene European hominin sample when compared to a sample of the same time depth from Africa. Some of the features examined followed the predictions of the accretion model and relate the middle Pleistocene European material to the later Neanderthals. However, although our analysis showed a clear separation between Neanderthals and early/recent modern humans and morphological proximity between European specimens from OIS 7 to 3, it also shows that the European hominins from the first half of the middle Pleistocene still shared most of their cranio-facial architecture with their African contemporaries., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

With the exception of Neanderthals, from which DNA sequences of numerous individuals have now been determined, the number and genetic relationships of other hominin lineages are largely unknown. Here we report a complete mitochondrial (mt) DNA sequence retrieved from a bone excavated in 2008 in Denisova Cave in the Altai Mountains in southern Siberia. It represents a hitherto unknown type of hominin mtDNA that shares a common ancestor with anatomically modern human and Neanderthal mtDNAs about 1.0 million years ago. This indicates that it derives from a hominin migration out of Africa distinct from that of the ancestors of Neanderthals and of modern humans. The stratigraphy of the cave where the bone was found suggests that the Denisova hominin lived close in time and space with Neanderthals as well as with modern humans.

Background: Reconstructing the dispersal patterns of extinct hominins remains a challenging but essential goal. One means of supplementing fossil evidence is to utilize archaeological evidence in the form of stone tools. Based on broad dating patterns, it has long been thought that the appearance of Acheulean handaxe technologies outside of Africa was the result of hominin dispersals, yet independent tests of this hypothesis remain rare. Cultural transmission theory leads to a prediction of a strong African versus non-African phylogeographic pattern in handaxe datasets, if the African Acheulean hypothesis is to be supported., Methodology/principal Findings: Here, this prediction is tested using an intercontinental dataset of Acheulean handaxes and a biological phylogenetic method (maximum parsimony). The analyses produce a tree consistent with the phylogeographic prediction. Moreover, a bootstrap analysis provides evidence that this pattern is robust, and the maximum parsimony tree is also shown to be statistically different from a tree constrained by stone raw materials., Conclusions/significance: These results demonstrate that nested analyses of behavioural data, utilizing methods drawn from biology, have the potential to shed light on ancient hominin dispersals. This is an encouraging prospect for human palaeobiology since sample sizes for lithic artefacts are many orders of magnitude higher than those of fossil data. These analyses also suggest that the sustained occurrence of Acheulean handaxe technologies in regions such as Europe and the Indian subcontinent resulted from dispersals by African hominin populations.

We report here on the direct isotopic evidence for Neanderthal and early modern human diets in Europe. Isotopic methods indicate the sources of dietary protein over many years of life, and show that Neanderthals had a similar diet through time (approximately 120,000 to approximately 37,000 cal BP) and in different regions of Europe. The isotopic evidence indicates that in all cases Neanderthals were top-level carnivores and obtained all, or most, of their dietary protein from large herbivores. In contrast, early modern humans (approximately 40,000 to approximately 27,000 cal BP) exhibited a wider range of isotopic values, and a number of individuals had evidence for the consumption of aquatic (marine and freshwater) resources. This pattern includes Oase 1, the oldest directly dated modern human in Europe (approximately 40,000 cal BP) with the highest nitrogen isotope value of all of the humans studied, likely because of freshwater fish consumption. As Oase 1 was close in time to the last Neanderthals, these data may indicate a significant dietary shift associated with the changing population dynamics of modern human emergence in Europe.

Studies of worldwide human variation have discovered three trends in summary statistics as a function of increasing geographic distance from East Africa: a decrease in heterozygosity, an increase in linkage disequilibrium (LD), and a decrease in the slope of the ancestral allele frequency spectrum. Forward simulations of unlinked loci have shown that the decline in heterozygosity can be described by a serial founder model, in which populations migrate outward from Africa through a process where each of a series of populations is formed from a subset of the previous population in the outward expansion. Here, we extend this approach by developing a retrospective coalescent-based serial founder model that incorporates linked loci. Our model both recovers the observed decline in heterozygosity with increasing distance from Africa and produces the patterns observed in LD and the ancestral allele frequency spectrum. Surprisingly, although migration between neighboring populations and limited admixture between modern and archaic humans can be accommodated in the model while continuing to explain the three trends, a competing model in which a wave of outward modern human migration expands into a series of preexisting archaic populations produces nearly opposite patterns to those observed in the data. We conclude by developing a simpler model to illustrate that the feature that permits the serial founder model but not the archaic persistence model to explain the three trends observed with increasing distance from Africa is its incorporation of a cumulative effect of genetic drift as humans colonized the world.

Western Eurasia yielded a rich Middle (MP) and Late Pleistocene (LP) fossil record documenting the evolution of the Neandertals that can be analyzed in light of recently acquired paleogenetical data, an abundance of archeological evidence, and a well-known environmental context. Their origin likely relates to an episode of recolonization of Western Eurasia by hominins of African origin carrying the Acheulean technology into Europe around 600 ka. An enhancement of both glacial and interglacial phases may have played a crucial role in this event, as well as in the subsequent evolutionary history of the Western Eurasian populations. In addition to climatic adaptations and an increase in encephalization, genetic drift seems to have played a major role in their evolution. To date, a clear speciation event is not documented, and the most likely scenario for the fixation of Neandertal characteristics seems to be an accretion of features along the second half of the MP. Although a separation time for the African and Eurasian populations is difficult to determine, it certainly predates OIS 11 as phenotypic Neandertal features are documented as far back as and possibly before this time. It is proposed to use the term "Homo rhodesiensis" to designate the large-brained hominins ancestral to H. sapiens in Africa and at the root of the Neandertals in Europe, and to use the term "Homo neanderthalensis" to designate all of the specimens carrying derived metrical or non-metrical features used in the definition of the LP Neandertals.

A procedure is outlined for distinguishing among competing hypotheses for fossil morphology and then used to evaluate current views on the meaning of Neandertal skeletal morphology. Three explanations have dominated debates about the meaning of Neandertal cranial features: climatic adaptation, anterior dental loading, and genetic drift. Neither climatic adaptation nor anterior dental loading are well supported, but genetic drift is consistent with the available evidence. Climatic adaptation and activity patterns are the most discussed explanations for Neandertal postcranial features. Robust empirical relationships between climate and body form in extant humans and other endotherms currently make climatic adaptation the most plausible explanation for the wide bodies and relatively short limbs of Neandertals, and many additional postcranial features are likely secondary consequences of these overall skeletal proportions. Activity patterns may explain certain Neandertal postcranial features, but unlike the situation for climate, relationships in extant humans between morphology and activities are typically not well established. For both the cranium and the postcranium, changes in diet or activity patterns may underlie why Neandertals and Pleistocene modern humans tend to be more robust than Holocene humans.

Recent investigations into the origins of symbolism indicate that personal ornaments in the form of perforated marine shell beads were used in the Near East, North Africa, and SubSaharan Africa at least 35 ka earlier than any personal ornaments in Europe. Together with instances of pigment use, engravings, and formal bone tools, personal ornaments are used to support an early emergence of behavioral modernity in Africa, associated with the origin of our species and significantly predating the timing for its dispersal out of Africa. Criticisms have been leveled at the low numbers of recovered shells, the lack of secure dating evidence, and the fact that documented examples were not deliberately shaped. In this paper, we report on 25 additional shell beads from four Moroccan Middle Paleolithic sites. We review their stratigraphic and chronological contexts and address the issue of these shells having been deliberately modified and used. We detail the results of comparative analyses of modern, fossil, and archaeological assemblages and microscopic examinations of the Moroccan material. We conclude that Nassarius shells were consistently used for personal ornamentation in this region at the end of the last interglacial. Absence of ornaments at Middle Paleolithic sites postdating Marine Isotope Stage 5 raises the question of the possible role of climatic changes in the disappearance of this hallmark of symbolic behavior before its reinvention 40 ka ago. Our results suggest that further inquiry is necessary into the mechanisms of cultural transmission within early Homo sapiens populations.

Approximately 700,000 years ago, Homo erectus in Africa was giving way to populations with larger brains accompanied by structural adjustments to the vault, cranial base, and face. Such early Middle Pleistocene hominins were not anatomically modern. Their skulls display strong supraorbital tori above projecting faces, flattened frontals, and less parietal expansion than is the case for Homo sapiens. Postcranial remains seem also to have archaic features. Subsequently, some groups evolved advanced skeletal morphology, and by ca. 200,000 years ago, individuals more similar to recent humans are present in the African record. These fossils are associated with Middle Stone Age lithic assemblages and, in some cases, Acheulean tools. Crania from Herto in Ethiopia carry defleshing cutmarks and superficial scoring that may be indicative of mortuary practices. Despite these signs of behavioral innovation, neither the Herto hominins, nor others from Late Pleistocene sites such as Klasies River in southern Africa and Skhūl/Qafzeh in Israel, can be matched in living populations. Skulls are quite robust, and it is only after approximately 35,000 years ago that people with more gracile, fully modern morphology make their appearance. Not surprisingly, many questions concerning this evolutionary history have been raised. Attention has centered on systematics of the mid-Pleistocene hominins, their paleobiology, and the timing of dispersals that spread H. sapiens out of Africa and across the Old World. In this report, I discuss structural changes characterizing the skulls from different time periods, possible regional differences in morphology, and the bearing of this evidence on recognizing distinct species.

Hepatitis B viruses (HBVs) represent a serious public health problem affecting 350 to 400 million HBV carriers worldwide. The virus does not exclusively infect humans, but can also be found in non-human primates as in the families Hominidae (chimpanzee, gorilla, orangutan) and Hylobatidae (gibbon), which are distributed over Africa (chimpanzee and gorilla) and Southeast Asia (orangutan and gibbon), the endemic areas of human HBV. The prevalence of asymptomatic HBV carriers reaches in gibbons 23-33% and in orangutans 15%. The genome organization of non-human primate HBVs is nearly identical to that of human HBVs. Because of this close similarity, the question of cross-transmission of HBV between species has arisen. There are many data on cross-transmission of human HBVs to the non-human primates. However, a cross-transmission of HBVs from non-human primates to humans has not been reported yet. Using more advanced diagnostic methods, the non-human primates have increasingly been identified as a reservoir of several viruses such as lymphocryptoviruses, Cercopithecine herpesvirus 1 (CeHV-1), Simian immunodeficiency virus (SIV), Simian foamy virus (SFV), and HBVs. Thus veterinarians, zookeepers, or people in close contact with non-human primates may potentially become infected with those viruses causing severe diseases. Enhanced awareness of prevalence, genetic relatedness and evolution of non-human primate HBVs will help prevent further spread and cross-transmission of these viruses between humans and non-human primates.

The earliest record of fossil apes outside Africa is in the latest early Miocene of Turkey and eastern Europe. There were at least 2, and perhaps 4, species of ape, which were found associated with subtropical mixed environments of forest and more open woodland. Postcranial morphology is similar to that of early Miocene primates and indicates mainly generalized arboreal quadrupedal behaviours similar to those of less specialized New World monkeys such as Cebus. Robust jaws and thick enamelled teeth indicate a hard fruit diet. The 2 best known species of fossil ape are known from the site of Paşalar in Turkey. They have almost identical molar and jaw morphology. Molar morphology is also similar to that of specimens from Germany and Slovakia, but there are significant differences in the anterior teeth of the 2 Paşalar species. The more common species, Griphopithecus alpani, shares mainly primitive characters with early and middle Miocene apes in Africa, and it is most similar phenetically to Equatorius africanus from Maboko Island and Kipsaramon. The second species is assigned to a new species of Kenyapithecus, an African genus from Fort Ternan in Kenya, on the basis of a number of shared derived characters of the anterior dentition, and it is considered likely that there is a phylogenetic link between them. The African sites all date from the middle Miocene, similar in age to the Turkish and European ones, and the earliest emigration of apes from Africa coincides with the closure of the Tethys Sea preceding the Langhian transgression. Environments indicated for the African sites are mixtures of seasonal woodlands with some forest vegetation. The postcrania of both African taxa again indicate generalized arboreal adaptation but lacking specialized arboreal function. This middle Miocene radiation of both African and non-African apes was preceded by a radiation of arboreal catarrhine primates in the early Miocene, among which were the earliest apes. The earliest Miocene apes in the genus Proconsul and Rangwapithecus were arboreal, and because of their association with the fruits of evergreen rain forest plants at Mfwangano Island, it would appear that they were forest adapted, i.e. were living in multi-storied evergreen forest. The same or similar species of the same genera from Rusinga Island, together with other genera such as Nyanzapithecus and the small ape Limnopithecus, were associated with plants and animals indicating seasonal woodland environments, probably with gallery forest forming corridors alongside rivers. While the stem ancestors of the Hominoidea were almost certainly forest adapted, the evidence of environments associated with apes in the later part of the early Miocene and the middle Miocene of East Africa indicates more seasonal woodlands, similar to those reconstructed for the middle Miocene of Paşalar in Turkey. This environmental shift was probably a requisite for the successful emigration of apes out of Africa and made possible later movement between the continents for much of the middle Miocene, including possible re-entry of at least one ape lineage back into Africa., (Copyright 2007 S. Karger AG, Basel.)

The past decade has seen the Pliocene and Pleistocene fossil hominin record enriched by the addition of at least ten new taxa, including the Early Pleistocene, small-brained hominins from Dmanisi, Georgia, and the diminutive Late Pleistocene Homo floresiensis from Flores, Indonesia. At the same time, Asia's earliest hominin presence has been extended up to 1.8 Myr ago, hundreds of thousands of years earlier than previously envisaged. Nevertheless, the preferred explanation for the first appearance of hominins outside Africa has remained virtually unchanged. We show here that it is time to develop alternatives to one of palaeoanthropology's most basic paradigms: 'Out of Africa 1'.

This paper proposes a statistical test of the single-species hypothesis using non-metric characters as a complement to statistical tests using more traditional metric characters. The sample examined is that of Asian and African Homo erectus. The paleoanthropological community is divided on the taxonomic distinction of these fossils, with workers arguing both for and against the species-level distinction between Asian and African populations. Previous arguments have focused on patterns of apparent morphological differentiation between the African and Asian cranial samples. To assess this question, three tests were performed that compared the range of variation in the fossil sample to a single-species group with a similar geographic distribution; this comparative sample was composed of 221 modern humans from Africa and Asia. For the first test, 23 metric characters were analyzed on the fossil and comparative samples. Using resampling procedures, the variation for these characters was examined, recreating 1000 samples from the human analogs and comparing the CV distributions of these samples to the CVs of the fossil group. The second test used the metric data to calculate a Euclidean distance between the African and Asian fossil samples. This distance was compared to a distribution of Euclidean distances calculated between 1000 randomly selected samples of African and Asian modern humans. For the third test, a grading scale was created for ten non-metric characters that encompassed the total morphological variation found in the fossil and modern human samples. The Manhattan distance between the Asian and African fossil samples was calculated and compared to a distribution of distances calculated between 1000 randomly selected samples of African and Asian moderns. The first two tests, using the metric data, failed to falsify the null hypothesis. However, in the third test, using non-metric data, the total Manhattan distance for the fossil sample approached the 100th percentile of the resampled distances calculated from the moderns. The implications of the contrasting results are discussed.

Ten years ago, evidence from genetics gave strong support to the "recent African origin" view of the evolution of modern humans, which posits that Homo sapiens arose as a new species in Africa and subsequently spread, leading to the extinction of other archaic human species. Subsequent data from the nuclear genome not only fail to support this model, they do not support any simple model of human demographic history. In this paper, we study a process in which the modern human phenotype originates in Africa and then advances across the world by local demic diffusion, hybridization, and natural selection. While the multiregional model of human origins posits a number of independent single locus selective sweeps, and the "out of Africa" model posits a sweep of a new species, we study the intermediate case of a phenotypic sweep. Numerical simulations of this process replicate many of the seemingly contradictory features of the genetic data, and suggest that as much as 80% of nuclear loci have assimilated genetic material from non-African archaic humans.

Previous work by several researchers has suggested that the cranial sample from Zhoukoudian possesses a unique metric pattern relative to the African and Asian specimens assigned to Homo erectus. The current study readdresses this issue with an expanded fossil sample and a larger and more comprehensive set of cranial measurements. To test the patterns present in the assemblage, canonical variates analysis was performed using a covariance matrix generated from the Howells data set. From this, interindividual Mahalanobis distances were computed for the fossils. Random expectation statistics were then used to measure statistical significance of the Mahalanobis distances. The results show that the Zhoukoudian hominids exhibit a unique metric pattern not shared by the African and Indonesian crania sampled. In these tests the Hexian calvaria resembled the African and Indonesian specimens and differed significantly from the craniometric pattern seen in the Zhoukoudian fossils. The Zhoukoudian specimens are characterized by a wide midvault and relatively narrow occipital and frontal bones, while the African and Indonesian crania (including Hexian) have relatively broad frontal and occipital dimensions compared to their midvaults. These results do not suggest that a multiple-species scenario is necessary to encompass the variation present in the sample. Based on the current evidence it is more probable that this variation reflects polytypism influenced by environmental adaptation and/or genetic drift.

With the shift during the 1980s from a human-great ape ultimately to an orangutan-(gorilla-(human-chimp)) theory of relatedness, the search for chimpanzee-like features in early hominids intensified. Reconstructions of early hominids became caricatures of chimpanzees, not only in soft tissue features (e.g. the nasal region), but in supposed bony structures (e.g. an anteriorly and especially superiorly protruding a supraorbital torus with a distinct posttoral sulcus behind). In spite of rampant >>Panophilia,<< actual morphologies of the majority of early hominid specimens are those cited as uniting an orangutan clade. Those specimens that are >>chimpanzee-like<< are probably not cladistically hominid.

Pan and Gorilla taxonomy is currently in a state of flux, with the number of existing species and subspecies of common chimpanzee and gorilla having been recently challenged. While Pan and Gorilla systematics have been evaluated on the basis of craniometric and odontometric data, only a handful of studies have evaluated multivariate craniometric variation within P. troglodytes, and none have evaluated in detail mandibular variation in either P. troglodytes or Gorilla gorilla. In this paper, we examine ontogenetic and adult mandibular variation in Pan and Gorilla. We test the hypothesis that patterns and degrees of mandibular variation in Pan and Gorilla closely correspond to those derived from previous analyses of craniometric variation. We then use these data to address some current issues surrounding Pan and Gorilla taxonomy. Specifically, we evaluate the purported distinctiveness of P.t. verus from the other two subspecies of Pan troglodytes, and the recent proposals to recognize Nigerian gorillas as a distinct subspecies, Gorilla gorilla diehli, and to acknowledge mountain and lowland gorillas as two separate species. Overall, patterns and degrees of multivariate mandibular differentiation parallel those obtained previously for the cranium and dentition. Thus, differences among the three conventionally recognized gorilla subspecies are somewhat greater than among subspecies of common chimpanzees, but differences between P. paniscus and P. troglodytes are greater than those observed between any gorilla subspecies. In this regard, the mandible does not appear to be more variable, or of less taxonomic value, than the face and other parts of the cranium. There are, however, some finer differences in the pattern and degree of morphological differentiation in Pan and Gorilla, both with respect to cranial and dental morphology, and in terms of the application and manner of size adjustment. Mandibular differentiation supports the conventional separation of bonobos from chimpanzees regardless of size adjustment, but size correction alters the relative alignment of taxa. Following size correction, intergroup distances are greatest between P.t. verus and all other groups, but there is considerable overlap amongst chimpanzee subspecies. Amongst gorillas, the greatest separation is between eastern and western gorillas, but adjustment relative to palatal vs. basicranial length results in a greater accuracy of group classification for G.g. gorilla and G.g. graueri, and more equivalent intergroup distances amongst all gorilla groups. We find no multivariate differentiation of the Nigerian gorillas based on mandibular morphology, suggesting that the primary difference between Nigerian and other western lowland gorillas lies in the nuchal region. Though intergroup distances are greatest between P.t. verus and other chimpanzee subspecies, the degree of overlap amongst all three groups does not indicate a markedly greater degree of distinction in mandibular, as opposed to other morphologies. Finally, mandibular differentiation corroborates previous craniodental studies indicating the greatest distinction amongst gorillas is between eastern and western groups. Thus, patterns and degrees of mandibular variation are in agreement with other kinds of data that have been used to diagnose eastern and western gorillas as separate species.

A central issue in paleoanthropology is whether modern humans emerged in a single geographic area and subsequently replaced the preexisting people in other areas. Although the study of human mitochondrial DNAs supported this single-origin and complete-replacement model, a recent paper(1) argues that humans expanded out of Africa more than once and regionally interbred. However, both the genetic antiquity and the impact of the African contribution to modern Homo sapiens are so great as to view Africa as a central place of human evolution. Despite the possibility that out-of-Africa H. sapiens interbred with other populations, this evidence is more consistent with the uniregional hypothesis than the multiregional hypothesis of modern human origins., (Copyright 2002 Wiley Periodicals, Inc.)

Another hominid skull has been recovered at Dmanisi (Republic of Georgia) from the same strata in which hominid remains have been reported previously. The Dmanisi site dated to approximately 1.75 million years ago has now produced craniofacial portions of several hominid individuals, along with many well-preserved animal fossils and quantities of stone artifacts. Although there are certain anatomical differences among the Dmanisi specimens, the hominids do not clearly represent more than one taxon. We assign the new skull provisionally to Homo erectus (=ergaster). The Dmanisi specimens are the most primitive and small-brained fossils to be grouped with this species or any taxon linked unequivocally with genus Homo and also the ones most similar to the presumed habilis-like stem. We suggest that the ancestors of the Dmanisi population dispersed from Africa before the emergence of humans identified broadly with the H. erectus grade.

The question of the mode of origin of modern humans (Homo sapiens) has dominated palaeoanthropological debate over the last decade. This review discusses the main models proposed to explain modern human origins, and examines relevant fossil evidence from Eurasia, Africa and Australasia. Archaeological and genetic data are also discussed, as well as problems with the concept of 'modernity' itself. It is concluded that a recent African origin can be supported for H. sapiens, morphologically, behaviourally and genetically, but that more evidence will be needed, both from Africa and elsewhere, before an absolute African origin for our species and its behavioural characteristics can be established and explained.

We have analyzed 35 widely distributed, polymorphic Alu loci in 715 individuals from 31 world populations. The average frequency of Alu insertions (the derived state) is lowest in Africa (.42) but is higher and similar in India (.55), Europe (.56), and Asia (.57). A comparison with 30 restriction-site polymorphisms (RSPs) for which the ancestral state has been determined shows that the frequency of derived RSP alleles is also lower in Africa (.35) than it is in Asia (.45) and in Europe (.46). Neighbor-joining networks based on Alu insertions or RSPs are rooted in Africa and show African populations as separate from other populations, with high statistical support. Correlations between genetic distances based on Alu and nuclear RSPs, short tandem-repeat polymorphisms, and mtDNA, in the same individuals, are high and significant. For the 35 loci, Alu gene diversity and the diversity attributable to population subdivision is highest in Africa but is lower and similar in Europe and Asia. The distribution of ancestral alleles is consistent with an origin of early modern human populations in sub-Saharan Africa, the isolation and preservation of ancestral alleles within Africa, and an expansion out of Africa into Eurasia. This expansion is characterized by increasing frequencies of Alu inserts and by derived RSP alleles with reduced genetic diversity in non-African populations.

East Asia is one of the few regions in the world where a relatively large number of human fossils have been unearthed--a discovery that has been taken as evidence for an independent local origin of modern humans outside of Africa. However, genetic studies conducted in the past ten years, especially using Y chromosomes, have provided unequivocal evidence for an African origin of East Asian populations. The genetic signatures present in diverse East Asian populations mark the footsteps of prehistoric migrations that occurred tens of thousands of years ago.

Archaeological excavations at the site of Dmanisi in the Republic of Georgia have uncovered two partial early Pleistocene hominid crania. The new fossils consist of a relatively complete cranium and a second relatively complete calvaria from the same site and stratigraphic unit that yielded a hominid mandible in 1991. In contrast with the uncertain taxonomic affinity of the mandible, the new fossils are comparable in size and morphology with Homo ergaster from Koobi Fora, Kenya. Paleontological, archaeological, geochronological, and paleomagnetic data from Dmanisi all indicate an earliest Pleistocene age of about 1.7 million years ago, supporting correlation of the new specimens with the Koobi Fora fossils. The Dmanisi fossils, in contrast with Pleistocene hominids from Western Europe and Eastern Asia, show clear African affinity and may represent the species that first migrated out of Africa.

The middle Miocene hominoid Otavipithecus namibiensis is the first and most complete fossil ape from sub-equatorial Africa and represents a significant addition to the taxonomically sparse African middle Miocene hominoid fossil record. The Otavipithecus hypodigm comprises the holotype mandible, which presents a unique mosaic of dental and gnathic characters, and several attributed cranial and postcranial elements which resemble the stem hominoid Proconsul. Contrary to initial hopes that this discovery would provide new insights into hominoid morphological diversity and phylogenetic relationships, a variety of conflicting phylogenetic hypotheses have been advanced suggesting ties to virtually every major large-bodied hominoid group (Conroy et al., 1992; Andrews, 1992 a; Conroy, 1994; Pickford et al., 1994; Begun, 1994 a). Cladistic analysis of a matrix of 22 qualitative and ten quantitative characters of the mandible and mandibular dentition found no support for a close phylogenetic relationship between Otavipithecus and either the African ape or great ape clades, or with any of the Eurasian fossil hominoids with which it has previously been compared. A close relationship between Otavipithecus and Kenyapithecus cannot be ruled out, but is deemed unlikely on the basis both of morphological comparisons and the absence of support within a cladistic framework. The present analysis indicates that Otavipithecus is most closely related to Afropithecus, as previously suggested by Andrews (1992 a) among others. Due to lack of statistical support for this result, a conservative interpretation, that these taxa represented related but divergent lineages of a late early Miocene hominoid radiation, is currently favored. Findings are consistent with the allocation of Otavipithecus to Andrews' (1992 a) tribe Afropithecini which represents the sister group to Kenyapithecus and the extant ape clade., (Copyright 2000 Academic Press.)

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., (Copyright 1999 Academic Press.)

A descriptive and comparative study of the human dental remains recovered from level six (Aurora stratum) of the Gran Dolina (TD) site, Sierra de Atapuerca, northern Spain, is presented. The TD6 dental sample consists of two deciduous and 28 permanent teeth, belonging to a minimum of six individuals. Paleomagnetic analyses of the TD sequence suggest an age for the Aurora stratum of greater than 780 ka. The associated fossil macro- and micrommals are consistent with a date for the Atapuerca-TD6 hominids at the end of the Early Pleistocene. As a whole, the size of the TD6 teeth is large and comparable to that of the African Lower Pleistocene hominids. Most morphological dental traits are plesiomorphic for the genus Homo, whereas the shape analysis has revealed some size-related trends that differ from those seen in early Homo. Thus, the relative size increase of the maxillary and mandibular anterior teeth and buccolingual diameter of the first molars, the reduction of the third molars and lower canines, and the P(3)>P(4)size sequence are all characteristic of the population represented by the TD6 hominids. The morphological evidence suggests that the TD6 hominids are closer to African Lower and early Middle Pleistocene hominids than they are to European Middle Pleistocene hominids. However, some dental traits of the TD6 hominids, such as the expansion of the anterior teeth, the P(3)>P(4)size sequence, and the morphology of the lower canine also suggest an evolutionary continuity between the population represented by these hominids and the European Middle Pleistocene population. Furthermore, dental evidence indicates that the TD6 hominids are clearly distinct from Asian H. erectus. Dental evidence also suggests that the TD6 hominids could represent an evolutionary connection between H. ergaster and H. heidelbergensis., (Copyright 1999 Academic Press.)

We examined the biogeographic patterns implied by early hominid phylogenies and compared them to the known dispersal patterns of Plio-Pleistocene African mammals. All recent published phylogenies require between four and seven hominid dispersal events between southern Africa, eastern Africa, and the Malawi Rift, a greater number of dispersals than has previously been supposed. Most hominid species dispersed at the same time and in the same direction as other African mammals. However, depending on the ages of critical hominid specimens, many phylogenies identify at least one hominid species that dispersed in the direction opposite that of contemporaneous mammals. This suggests that those hominids may have possessed adaptations that allowed them to depart from continental patterns of mammalian dispersal.

The robust australopithecines were a side branch of human evolution. They share a number of unique craniodental features that suggest their monophyletic origin. However, virtually all of these traits appear to reflect a singular pattern of nasomaxillary modeling derived from their unusual dental proportions. Therefore, recent cladistic analyses have not resolved the phylogenetic history of these early hominids. Efforts to increase cladistic resolution by defining traits at greater levels of anatomical detail have instead introduced substantial phyletic error.