Recent African Origin Model Research Articles

The development of ideas about a recent African origin for Homo sapiens.

In this contribution I will review the development of ideas about a recent African origin for our species over the last 50 years, starting from the time of my PhD in the early 1970s. I will examine the instructive and quite different interpretations placed on the 1979 discovery of a partial Neanderthal skeleton associated with a Châtelperronian industry at the rock shelter of St-Césaire in France, and then focus on the crucial years from 1987-1989, including the so-called 'Human Revolution' conference of 1987, and my 1988 Science paper with Peter Andrews: 'Genetic and Fossil Evidence for the Origin of Modern Humans'. Following the historical review, I will assess the status of five proposed models for the evolution of derived Homo sapiens: Recent African Origin (RAO); RAO and Hybridisation (RAOH); Assimilation (AM); Multiregional Evolution (MRE); and Braided Stream (BS). I conclude that a recent African origin model with hybridization (RAOH) is the best supported from the fossil and genetic evidence.

Dental Morphological Affinities Among Late-Pleistocene and Recent Humans

The study uses analyses of Mean Measure of Divergence (MMD) to assess the affinities of ten populations representing early anatomically modern humans, Upper Paleolithic Europeans, recent modern humans, and Neandertals. The 18-triat MMD analysis demonstrates that, dentally, Neandertals are quite divergent from all modern humans. The results of cluster analyses based on MMD values suggest two major clusters: Neandertals and modern humans. The data also suggest two sub-clusters within the modern human cluster. One links Upper Paleolithic Europeans with recent North Africans and Europeans. The other links early anatomically modern humans with Late Pleistocene Africans and recent Sub-Saharan Africans. These results do not support a close relationship between Neandertals and any modern human groups samples. They also tentatively suggest that, if the two populations were interbreeding, it is not reflected in their dental morphology. The results showing a close affinity between early anatomically modern humans and Sub-Saharan Africans are consist with the Recent African Origin model for modern human origins.

Out of Africa, with a difference

Anthropology According to the recent African origin model, modern humans emerged in Africa by about 200,000 years ago. They spread across the rest of the world, successively replacing archaic populations along the way. In a Perspective, Galway-Witham and Stringer show that recent evidence calls for

Discovery of the Fuyan teeth: challenging or complementing the out-of-Africa scenario?

Discovery of the Fuyan teeth: challenging or complementing the out-of-Africa scenario?

Right for the Wrong Reasons

The sequencing of the Neanderthal genome answered once and for all the question of whether these hominins played a role in the origins of modern humans—they did, and a majority of humans alive today retain a small portion of Neanderthal genes. This finding rejects the strictest versions of the Recent African Origin model and has been celebrated by supporters of Multiregional Evolution (MRE). However, we argue that MRE can also be rejected and that other, intermediate, models of modern human origins better represent the means by which modern humans became the only extant human species. We argue this because we reject one of the major tenets of MRE: global gene flow that prevents cladogenesis from occurring. First, using reconstructions of Pleistocene hominin census size, we maintain that populations were neither large nor dense enough to result in such high levels of gene flow across the Old World. Second, we use mammalian divergence and hybridization data to show that the emergence of Homo is recent enoug...

Tracing Our Lineage: Molecular Contributions to the Construction of the Human Phylogeny

One of the most novel and important contributions to biological anthropology in the last two decades has been the implementation of the techniques of molecular genetics to address some of the field’s fundamental debates. The ordering of the extant hominids into monophyletic clades has long been a source of contention, with human-chimpanzee, human-gorilla, and human-orangutan clades being proposed in various studies. An expanding genetic analysis culminating in over 20,000 sequence alignments of all extant hominids has shown that chimpanzees and humans form a monophyletic clade, the closest relative of which is the gorilla. Since the discovery of the first Neandertal specimens there has also been a sometimes vicious dichotomy between those that advocate interbreeding between modern humans and Neandertals (The Multiregional Continuity Model), and those who maintain that modern humans replaced all other hominids with absolutely no interbreeding (The Recent African Origin Model). Analysis of mitochondrial DNA accompanied by a draft sequence of the Neandertal nuclear genome has called into question the validity of both paradigms and promoted the emergence of a compromise in the form of The Partial Replacement Model. Finally, the debate on the division of the human species into geographic races has been raging for centuries. Genetic comparisons between populations demonstrate that the total amount of human variation is in fact very small and provides no basis for the concept of biologically distinct races. The contributions of molecular genetics to biological anthropology are inestimable and will only continue to increase as technological advances are made.

Archaic human genomics

For much of the 20th century, the predominant view of human evolutionary history was derived from the fossil record. Homo erectus was seen arising in Africa from an earlier member of the genus and then spreading throughout the Old World and into the Oceania. A regional continuity model of anagenetic change from H. erectus via various intermediate archaic species into the modern humans in each of the regions inhabited by H. erectus was labeled the multiregional model of human evolution (MRE). A contrasting model positing a single origin, in Africa, of anatomically modern H. sapiens with some populations later migrating out of Africa and replacing the local archaic populations throughout the world with complete replacement became known as the recent African origin (RAO) model. Proponents of both models used different interpretations of the fossil record to bolster their views for decades. In the 1980s, molecular genetic techniques began providing evidence from modern human variation that allowed not only the different models of modern human origins to be tested but also the exploration demographic history and the types of selection that different regions of the genome and even specific traits had undergone. The majority of researchers interpreted these data as strongly supporting the RAO model, especially analyses of mitochondrial DNA (mtDNA). Extrapolating backward from modern patterns of variation and using various calibration points and substitution rates, a consensus arose that saw modern humans evolving from an African population around 200,000 years ago. Much later, around 50,000 years ago, a subset of this population migrated out of Africa replacing Neanderthals in Europe and western Asia as well as archaics in eastern Asia and Oceania. mtDNA sequences from more than two-dozen Neanderthals and early modern humans re-enforced this consensus. In 2010, however, the complete draft genomes of Neanderthals and of heretofore unknown hominins from Siberia, called Denisovans, demonstrated gene flow between these archaic human species and modern Eurasians but not sub-Saharan Africans. Although the levels of gene flow may be very limited, this unexpected finding does not fit well with either the RAO model or MRE model. More thorough sampling of modern human diversity, additional fossil discoveries, and the sequencing of additional hominin fossils are necessary to throw light onto our origins and our history.

The human lineage

The human lineage

The saltational model for the dawn of H. sapiens, chin, adolescence phase, complex language and modern behavior

AbstractA new model may contribute to resolve the origin problem of H. sapiens. According to our new viewpoint, Neandertals were neither one of our direct ancestors nor a different species. Their origin was not in Europe 150-200 or 300 thousand years ago. As for the origin of H. sapiens, it was neither in Africa roughly 2 million years ago nor roughly 200 thousand years ago. In other words, both the Multiregional model and the recent African origin model seem wrong. Our own species arose in the Middle East approximately 150 thousand years ago and split into two subspecies: Moderns and Neandertals. Rapid and radial expansion of H. sapiens from the origin implies a revolution (see Figure 1). Complex language, modern behavior and even adolescence phase plus chin might be included into the revolution. This possibility seems consistent with the data and could also be tested via; 1-the origin of complex language based on the modern human form of FOXP2 gene 2-the origin of adolescence or adolescent growth spurt 3- the genetic origin of the Flores hobbits. If all of these three origins appeared in the Levant about 150 thousand years ago then our model is true in all aspects. This speciation seems an unexpected revolution or macroevolution occured in several thousand years. The last pre-sapiens hominids may be extinct due to OIS 6 namely without replacement by sapiens.

Human Population Genetic Structure and Diversity Inferred from Polymorphic L1(LINE-1) and Alu Insertions

Background/Aims: The L1 retrotransposable element family is the most successful self-replicating genomic parasite of the human genome. L1 elements drive replication of Alu elements, and both have had far-reaching impacts on the human genome. We use L1 and Alu insertion polymorphisms to analyze human population structure. Methods: We genotyped 75 recent, polymorphic L1 insertions in 317 individuals from 21 populations in sub-Saharan Africa, East Asia, Europe and the Indian subcontinent. This is the first sample of L1 loci large enough to support detailed population genetic inference. We analyzed these data in parallel with a set of 100 polymorphic Alu insertion loci previously genotyped in the same individuals. Results and Conclusion: The data sets yield congruent results that support the recent African origin model of human ancestry. A genetic clustering algorithm detects clusters of individuals corresponding to continental regions. The number of loci sampled is critical: with fewer than 50 typical loci, structure cannot be reliably discerned in these populations. The inclusion of geographically intermediate populations (from India) reduces the distinctness of clustering. Our results indicate that human genetic variation is neither perfectly correlated with geographic distance (purely clinal) nor independent of distance (purely clustered), but a combination of both: stepped clinal.

Population extinction and recolonization in human demographic history

For over 30 years, a debate has raged among anthropologists about the origins of anatomically modern humans. At first the debate centered on fossil evidence, but in the past 10–15 years population geneticists have entered the fray. One model, the multiregional evolution model, posits a gradual transition from Homo erectus to anatomically modern humans throughout the Old World. In contrast, the recent African origin model hypothesizes that anatomically modern humans arose from a small, isolated population in Africa, spread out of Africa, and replaced indigenous H. erectus populations in Eurasia and Australasia. A primary objection, from a population genetics perspective, to the multiregional model is that the genetic data suggest a small effective population size for humans. This effective size is on the order of 10 000. Effective population size has a complex relationship with census size, but it has been argued that, assuming that effective size is roughly equal to the number of breeding individuals in human populations under standard demographic conditions, 10 000 breeding individuals could not have occupied much of the Old World throughout the Pleistocene and remained a cohesive species via gene flow. However, this argument is not valid if one considers population extinction and recolonization, which might have played an important role in human history during the Pleistocene. With population extinction and recolonization, the inbreeding effective population size can be small and the census size extremely large. In this paper, I will show that under conditions of population extinction and recolonization, an effective population size of 10 000 suggested by genetic data is compatible with a large census size consistent with the multiregional model.

DNA's evolutionary dilemma: Genetic studies collide with the mystery of human evolution

Just a few years ago, genetic researchers assumed the status of a scientific Supreme Court in the debate over humanity's prehistoric roots. The coils of human DNA appeared to have hardened into a molecular gavel with which these scientists could issue a final ruling on how best to explain the evolution of modern Homo sapiens. During the late 1980s, initial studies of global DNA diversity encouraged a vigorous bout of gavel pounding. One after another, investigators concluded that modern humans probably arose in Africa around 200,000 years ago and then spread elsewhere, replacing Neandertals and any other species in our evolutionary past. Analyses of DNA-inherited only through the maternal line-in people from different parts of the world traced the origin of these genes back to one or a few African women dubbed mitochondrial Eve. Decades of anthropological debate over modern human origins that was based on interpretations of measurements and a host of bumps and grooves on ancient fossils teetered on the verge of irrelevance. However, even some admirers of Eve now say that the jury is out on whether state-of-the-art DNA studies can live up to their early billing. Accumulating data prove compatible with either of the two main theories of how H. sapiens came about. The recent African-origin model championed by many genetic researchers relies on genetic findings that fit just as easily into a contrasting multiregional model. That is, populations of H. sapiens living in different parts of Africa, Asia, and Europe interbred enough over at least the past 1 million years to evolve collectively as a single species. The various populations around the world derived from even older ancestors of H. sapiens in this scenario. Practitioners of what has been dubbed anthropological genetics now operate with a sense of caution and a hunger for better explanations of how evolutionary forces produce genetic diversity among individuals and groups. A lot of us have been too eager to assume that a strict out-of-Africa model is correct because it's compatible with the genetic data, without considering that the data also fit with the multiregional theory, says anthropologist John H. Relethford of the State University of New York at Oneonta. It's time to go back to the drawing board on this issue.

GENETICS OF MODERN HUMAN ORIGINS AND DIVERSITY

▪ Abstract A major and continuing debate in anthropology concerns the question of whether modern Homo sapiens emerged as a separate species roughly 200,000 years ago in Africa (recent African origin model) or as the consequence of evolution within a polytypic species spread across several regions of the Old World (multiregional model). Genetic data have been used to address this debate, focusing on the analysis of gene trees, genetic diversity within populations, and genetic differences between populations. Although the genetic data do provide support for the recent African origin model, they also are compatible with the multiregional model. The genetic evidence provides little direct inference regarding phylogeny, but it can tell us a great deal about ancient demography. Currently, neither model of modern human origins is unequivocally supported to the exclusion of the other.

A Global Haplotype Analysis of the Myotonic Dystrophy Locus: Implications for the Evolution of Modern Humans and for the Origin of Myotonic Dystrophy Mutations

Haplotypes consisting of the (CTG)n repeat, as well as several flanking markers at the myotonic dystrophy (DM) locus, were analyzed in normal individuals from 25 human populations (5 African, 2 Middle Eastern, 3 European, 6 East Asian, 3 Pacific/Australo-Melanesian, and 6 Amerindian) and in five nonhuman primate species. Non-African populations have a subset of the haplotype diversity present in Africa, as well as a shared pattern of allelic association. (CTG)18-35 alleles (large normal) were observed only in northeastern African and non-African populations and exhibit strong linkage disequilibrium with three markers flanking the (CTG)n repeat. The pattern of haplotype diversity and linkage disequilibrium observed supports a recent African-origin model of modern human evolution and suggests that the original mutation event that gave rise to DM-causing alleles arose in a population ancestral to non-Africans prior to migration of modern humans out of Africa.

Genetics and modern human origins

AbstractThe past decade has brought considerable debate on the subject of modern human origins. The nature of the transition from Homo erectus to archaic Homo sapiens to modern H. sapiens has been examined primarily in terms of the relative contribution of archaic populations to later moderns, both within and among geographic regions. The recent African origin model proposes that modern humans appeared first in Africa between 100,000 and 200,000 years ago, and then spread through the rest of the Old World, replacing preexisting populations.1–6 This model has been referred to by a variety of names, including “replacement”, “Garden of Eden”, “Noah's Ark”, and “out of Africa”. The recent African origin model contrasts with the multiregional model, which proposes a species‐wide transition to modern humans throughout the Old World during the past million years or more.7–10 Indeed, some proponents of the multiregional model advocate placing Homo erectus and all subsequent species of Homo in the evolutionary species Homo sapiens.11 This contrasts with the view that there were multiple hominid species during the Middle Pleistocene. The debate continues.12,13 Although the multiregional model is often portrayed as proposing a simultaneous transition to anatomically modern humans in different geographic regions, it explicitly allows for varying degrees of continuity across time and space.10 This model, in the broad sense, does not rule out the possibility that modern human morphology appeared first in Africa and then spread through the rest of the Old World through gene flow. However, not all advocates of the multiregional model adhere to this specific subset of the general model.9Comparison of the African and multiregional models is complicated by considering other, less extreme, hypotheses. Some versions of the recent African origin model imply a speciation event associated with the initial origin of modern humans. Another version, which suggests the possibility of some admixture between “moderns” leaving Africa and preexisting “archaics” elsewhere in the Old World,14,15 is similar to some variants of the multiregional model, which also suggest that modern morphology appeared first in Africa, but involved admixture with other Old World populations.16 The major difference between these views appears to be the extent of admixture, although the exact level is never specified. A further complication is the possibility that multiple dispersals from Africa produced a more complicated pattern of worldwide variation.17