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Background: The molecular clock is an important genetic tool for estimating evolutionary timescales. However, the detection of a time-dependent effect on substitution rate estimates complicates its application. It has been suggested that demographic processes could be the main cause of this confounding effect. In the present study, I propose a new algorithm for estimating the coalescent age of phylogenetically related sequences, taking into account the observed time-dependent effect on the molecular rate detected by others. Results: By applying this method to real human mitochondrial DNA trees with shallow and deep topologies, I obtained significantly older molecular ages for the main events of human evolution than were previously estimated. These ages are in close agreement with the most recent archaeological and paleontological records favoring the emergence of early anatomically modern humans in Africa 315 ± 34 thousand years ago (kya) and the presence of recent modern humans outside of Africa as early as 174 ± 48 thousand years ago. Furthermore, during the implementation process, I demonstrated that in a population with fluctuating sizes, the probability of fixation of a new neutral mutant depends on the effective population size, which is in better accordance with the fact that under the neutral theory of molecular evolution, the fate of a molecular mutation is mainly determined by random drift. Conclusions: I suggest that the demographic history of populations has a more decisive effect than purifying selection and/or mutational saturation on the time-dependent effect observed for the substitution rate, and I propose a new method that corrects for this effect. [ABSTRACT FROM AUTHOR]

El artículo discurre sobre los homo sapiens, la teoría de evolución del teórico inglés Charles Darwin y la evolución humana. El autor comenta sobre el descubrimiento del fósil australopitecus afarensis se llama Lucy, la arquelogía y la historia en África y Europa.

The abundant evidence that Homo sapiens evolved in Africa within the past 200 000 years, and dispersed across the world only within the past 100 000 years, provides us with a strong framework in which to consider the evolution of human diversity. While there is evidence that the human capacity for culture has a deeper history, going beyond the origin of the hominin clade, the tendency for humans to form cultures as part of being distinct communities and populations changed markedly with the evolution of H. sapiens. In this paper, we investigate ‘cultures’ as opposed to ‘culture’, and the question of how and why, compared to biological diversity, human communities and populations are so culturally diverse. We consider the way in which the diversity of human cultures has developed since 100 000 years ago, and how its rate was subject to environmental factors. We argue that the causes of this diversity lie in the distribution of resources and the way in which human communities reproduce over several generations, leading to fissioning of kin groups. We discuss the consequences of boundary formation through culture in their broader ecological and evolutionary contexts. [ABSTRACT FROM AUTHOR]

A strong postzygotic reproductive barrier separates the recently diverged Asian and African cultivated rice species, Oryza sativa and O. glaberrima. Recently a model of genetic incompatibilities between three adjacent loci: S1A, S1 and S1B (called together the S1 regions) interacting epistatically, was postulated to cause the allelic elimination of female gametes in interspecific hybrids. Two candidate factors for the S1 locus (including a putative F-box gene) were proposed, but candidates for S1A and S1B remained undetermined. Here, to better understand the basis of the evolution of regions involved in reproductive isolation, we studied the genic and structural changes accumulated in the S1 regions between orthologous sequences. First, we established an 813 kb genomic sequence in O. glaberrima, covering completely the S1A, S1 and the majority of the S1B regions, and compared it with the orthologous regions of O. sativa. An overall strong structural conservation was observed, with the exception of three isolated regions of disturbed collinearity: (1) a local invasion of transposable elements around a putative F-box gene within S1, (2) the multiple duplication and subsequent divergence of the same F-box gene within S1A, (3) an interspecific chromosomal inversion in S1B, which restricts recombination in our O. sativa×O. glaberrima crosses. Beside these few structural variations, a uniform conservative pattern of coding sequence divergence was found all along the S1 regions. Hence, the S1 regions have undergone no drastic variation in their recent divergence and evolution between O. sativa and O. glaberrima, suggesting that a small accumulation of genic changes, following a Bateson-Dobzhansky-Muller (BDM) model, might be involved in the establishment of the sterility barrier. In this context, genetic incompatibilities involving the duplicated F-box genes as putative candidates, and a possible strengthening step involving the chromosomal inversion might participate to the reproductive barrier between Asian and African rice species. [ABSTRACT FROM AUTHOR]

In the process of proliferation from Africa, communities of Homo sapiens became more and more different in terms of the colour of their eyes and skin, the languages they spoke, the songs they sang, the animals they hunted or domesticated; now a reverse process seems to be slowly taking place. Of course, many differences remain and there is a strongly positive side to that. However, today in the emerging global megapolis, a painful process of assimilation is replacing the earlier process of dissimilation. The East and the West will probably meet somewhere in the middle ground; both not merely bringing their respective values to the evolving global normative synthesis, these values are being modified in this process. Neither exclusively “Eastern authoritarian collectivistic” nor “Western liberal individualistic” responses are adequate when facing contemporary challenges. In a sense, humankind may indeed be in the process of completing a full cycle: from a single community through the proliferation and diversification of communities towards the emergence of a community of communities that should become, in some important respects, more and more similar to each other, i.e., a slow and contradictory process of assimilation is replacing the millenia-long process of dissimilation. [ABSTRACT FROM PUBLISHER]

We suggest an ethno-biological approach to analyze the cultural and social drivers of hunting activities and assess sustainability in villages near Makokou, northeast Gabon, based on interviews with hunters, participatory mapping of hunting territories, and daily records of offtakes for 1 yr. Hunting in villages of northeast Gabon is practiced for both local consumption and cash income to cover basic family expenses. There appears to be no clear tendency to abandon subsistence hunting for commercial hunting as in other regions of Africa. Cultural and socioeconomic factors explain the temporal and spatial variation in hunting activities. Hunting increases in the dry season during circumcision ceremonies, when it is practiced mainly at > 10 km from villages, and decreases during the rainy season because most hunters are occupied by other economic activities. Degraded forest such as secondary regrowth supplies 20% of the animals killed and the greatest diversity of species at short distances from villages. Mature forest supplies the species with the greatest commercial value, e.g., red river hog (Potamochoerus porcus), and is the preferred source of meat for traditional ceremonies. In the last 15 yr, hunting patterns have changed rapidly, mainly because of the spread of gun hunting, which had serious implications for the nature of offtakes. Our results suggest that there is potential to allow hunting for resistant species such as blue duiker (Cephalophus monticola) and African brush-tailed porcupine (Atherurus africanus). Other species such as red river hog and small diurnal monkeys require more attention. Specific management systems could be discussed in participatory hunting management plans to identify possible solutions to maintain the population levels of the more critical species. [ABSTRACT FROM AUTHOR]

Discusses several theories of human anthropology concerning the Africa and the rest of the world evolutionary hypothesis. Assessment of the concept of continental divide; Weaknesses of the Multiregional Model; Trellis model of recurrent genetic interchange.

Cichlid fishes (Perciformes: Teleostei) found in the lakes of Africa have served as model systems for the study of evolution. The enormous number of species (1000 in Lake Malawi alone), the great diversity of trophic adaptations and behaviors, and the extreme rapidity of their divergence (<50,000 y for some faunas) single out these organisms as examples of evolution in progress. Because these fishes are confined to discrete lacustrine environments and their origination is bounded by geological features, these groups provide models with which to study evolution. We review theoretical studies and empirical research on the cichlid faunas of Africa to provide a synthetic overview of current knowledge of the evolutionary processes at work in this group. This view provides the critical information needed to formulate and test hypotheses that may permit discrimination among the diverse theories and models that have been advanced to explain the evolution of these fishes. [ABSTRACT FROM AUTHOR]

Abstract Aim We propose a phylogeny of selected Hyperolius species (Anura: Hyperoliidae), based on mtDNA sequence data and parsimony analysis. This phylogeny was used to interpret the historical biogeography of the genus in Africa. Location Samples were collected throughout the distribution of Hyperolius in Africa. Methods We compiled distributional maps of all species, summarized historical changes in vegetation and climate in Africa since the late Cretaceous, and used these in combination to identify historical factors that may have contributed to speciation in these frogs. A phylogeny for Hyperolius was derived from mtDNA sequence data and interpreted in terms of climatic and vegetation changes in Africa. Main conclusions Lowland rainforest is proposed to have been the ancestral habitat of Hyperolius . The expansion of savannah and reduction of lowland rainforest were identified as important factors in the differentiation of the more basal species. Finally, the development of the Rift Valley system played an important role in the speciation of derived species with relatively limited distributions. [ABSTRACT FROM AUTHOR]

The article focuses on the developments in hominid paleontology in Africa. New studies on the morphology of many specimens with a concomitant better appreciation of the total morphological pattern and of the ranges of variation within populations. The time scale of hominid evolution in East Africa is becoming progressively clearer with new age determinations based upon the potassium-argon method. It is becoming possible to formulate rentative synoptic models of the chronological and phylogenetic relationships between the South and East African fossil hominids and a single pattern of African hominid phylogeny.

Discusses the importance of ecology in the formation of species. How Charles Darwin got his ideas of species; Ecology being neglected in this century's evolutionary science; The ecological speciation model; Attention being given to environmental factors as well as genes; Bursts of speciation as seen in the cichlid fish in Africa's Lake Victoria; Study on marine and stream-dwelling stickleback fish from British Columbia and their genetically distant counterparts in Japan.

The article presents the author's comments on the study "Genes, Tribes, and the African History," by Scott Mac Eachern, which has been published within the issue. The author thinks that the development of greater chronological controls for rates of genetic change is very important. Referring to some of the social and political issues which accompany genetic research in Africa, the author feels the analysis given in the study should be extended.

The article reports on the production of two human genomes produced in Africa. The genomes are created of civil rights activist Desmond Tutu, and Gubi, a Namibian hunter-gatherer. Gubi, who belongs to the Khoisan community, is the first genome from the minority population of Africa and Tutu comes from the Bantu, the majority population in southern Africa. David Comas, a student of human diversity, states that the genomes will help in tracing the evolution and genetic differences in human beings.