Out Of Africa Research Articles

Phylogeography helps with investigating the building of human parasite communities

Phylogeography of parasites and microbes is a recent field. Phylogeographic studies have been performed mostly to test three major hypotheses that are not mutually exclusive on the origins and distributions of human parasites and microbes: (1) the "out of Africa" pattern where parasites are supposed to have followed the dispersal and expansion of modern humans in and out of Africa, (2) the "domestication" pattern where parasites were captured in the domestication centres and dispersed through them and (3) the "globalization" pattern, in relation to historical and more recent trade routes. With some exceptions, such studies of human protozoans, helminths and ectoparasites are quite limited. The conclusion emphasizes the need to acquire more phylogeographic data in non-Occidental countries, and particularly in Asia where all the animal domestications took place.

An Oblique Epistemic Defence of Conceptual Analysis

AbstractThis article argues, against contemporary experimentalist criticism, that conceptual analysis has epistemic value, with a structure that encourages the development of interesting hypotheses which are of the right form to be valuable in diverse areas of philosophy. The article shows, by analysis of the Gettier programme, that conceptual analysis shares the proofs and refutations form Lakatos identified in mathematics. Upon discovery of a counterexample, this structure aids the search for a replacement hypothesis. The search is guided by heuristics. The heuristics of conceptual analysis are similar to those in other interesting areas of scholarship, and so hypotheses generated by it are of the right form to be applicable to diverse areas. The article shows that the explanationist criterion in epistemology was developed and applied in this way. The epistemic value of conceptual analysis is oblique because it contributes not towards the main purpose of conceptual analysis but towards the reliable development of epistemically valuable hypotheses in philosophy and scholarship.

Single origin of human commensalism in the house sparrow

The current, virtually worldwide distribution of the house sparrow (Passer domesticus) is a result of its commensal relationship with humans. It has been suggested that long before the advent of agriculture, an early glacial advance resulted in two disjunct ranges of ancestral house sparrows - one in the Middle East and another on the Indian subcontinent. Differentiation during this period of isolation resulted in two major groups of subspecies: the domesticus group and the indicus group. According to this hypothesis, commensalism with humans would have evolved independently in the two regions and at least twice. An alternative hypothesis is that morphological differences between the subspecies represent very recent differentiation, following expansions from a single source. To test between these hypotheses, we analysed genetic variation at the mitochondrial DNA control region and at three nuclear loci from several house sparrow populations in Europe, Asia and North Africa. No differentiation between the indicus and domesticus groups was found, supporting the single origin hypothesis. One of the subspecies in the indicus group, P. d. bactrianus, differs ecologically from other house sparrows in being migratory and in preferentially breeding in natural habitat. We suggest that bactrianus represents a relict population of the ancestral, noncommensal house sparrow. When agricultural societies developed in the Middle East about 10 000 years ago, a local house sparrow population of the bactrianus type adapted to the novel environment and eventually became a sedentary, human commensal. As agriculture and human civilizations expanded, house sparrows experienced a correlated and massive expansion in range and numbers. The pattern of genetic variation analysed here is consistent with this scenario.

Monitoring adaptive genetic responses to environmental change

Widespread environmental changes including climate change, selective harvesting and landscape alterations now greatly affect selection regimes for most organisms. How animals and plants can adapt to these altered environments via contemporary evolution is thus of strong interest. We discuss how to use genetic monitoring to study adaptive responses via repeated analysis of the same populations over time, distinguishing between phenotypic and molecular genetics approaches. After describing monitoring designs, we develop explicit criteria for demonstrating adaptive responses, which include testing for selection and establishing clear links between genetic and environmental change. We then review a few exemplary studies that explore adaptive responses to climate change in Drosophila, selective responses to hunting and fishing, and contemporary evolution in Daphnia using resurrected resting eggs. We further review a broader set of 44 studies to assess how well they meet the proposed criteria, and conclude that only 23% fulfill all criteria. Approximately half (43%) of these studies failed to rule out the alternative hypothesis of replacement by a different, better-adapted population. Likewise, 34% of the studies based on phenotypic variation did not test for selection as opposed to drift. These shortcomings can be addressed via improved experimental designs and statistical testing. We foresee monitoring of adaptive responses as a future valuable tool in conservation biology, for identifying populations unable to evolve at sufficiently high rates and for identifying possible donor populations for genetic rescue. Technological advances will further augment the realization of this potential, especially next-generation sequencing technologies that allow for monitoring at the level of whole genomes.

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 complex origin of Astyanax cavefish

BackgroundThe loss of phenotypic characters is a common feature of evolution. Cave organisms provide excellent models for investigating the underlying patterns and processes governing the evolutionary loss of phenotypic traits. The blind Mexican cavefish, Astyanax mexicanus, represents a particularly strong model for both developmental and genetic analyses as these fish can be raised in the laboratory and hybridized with conspecific surface form counterparts to produce large F2 pedigrees. As studies have begun to illuminate the genetic bases for trait evolution in these cavefish, it has become increasingly important to understand these phenotypic changes within the context of cavefish origins. Understanding these origins is a challenge. For instance, widespread convergence on similar features renders morphological characters less informative. In addition, current and past gene flow between surface and cave forms have complicated the delineation of particular cave populations.ResultsPast population-level analyses have sought to: 1) estimate at what time in the geological past cave forms became isolated from surface-dwelling ancestors, 2) define the extent to which cave form populations originated from a common invasion (single origin hypothesis) or several invasions (multiple origin hypothesis), and 3) clarify the role of geological and climatic events in Astyanax cavefish evolution. In recent years, thanks to the combined use of morphological and genetic data, a much clearer picture has emerged regarding the origins of Astyanax cavefish.ConclusionsThe consensus view, based on several recent studies, is that cave forms originated from at least two distinct ancestral surface-dwelling stocks over the past several million years. In addition, each stock gave rise to multiple invasions of the subterranean biotope. The older stock is believed to have invaded the El Abra caves at least three times while the new stock separately invaded the northern Guatemala and western Micos caves. This renewed picture of Astyanax cavefish origins will help investigators draw conclusions regarding the evolution of phenotypic traits through parallelism versus convergence. Additionally, it will help us understand how the presence of cave-associated traits in old versus young cave populations may be influenced by the time since isolation in the cave environment. This will, in turn, help to inform our broader understanding of the forces that govern the evolution of phenotypic loss.

How to measure replacement: Auxiliary selection in Old Spanish bibles

Studies of the development of compound tense auxiliary selection in Spanish frequently analyse ser (‘to be’) + past participle (PtP) as an anterior construction, and its disappearance as a slow replacement process starting in Old Spanish, in which the new anterior auxiliary aver (‘to have’) replaced it. This article investigates and rejects the empirical basis for this claim on the basis of a comparative analysis of Old Spanish bible translations. It is argued that the majority of tokens of ser + PtP has a resultative function, as indicated by typical patterns of verbal mood, coordination and temporal-aspectual morphology. Old Spanish translators of the bible appear to have regarded aver + PtP as being more similar to simple imperfective preterit forms like cantaba (‘s/he sang’) than to ser + PtP. Comparing the types and rates of use of aver + PtP and ser + PtP in earlier and later bible versions with the help of generalised linear mixed-effects regression models shows that ser + PtP was more stable in Old Spanish than hitherto assumed. Rather than replacing ser + PtP in Old Spanish, aver + PtP expanded at the expense of simple preterit forms. In summary, this article provides empirical evidence against the replacement hypothesis for Old Spanish, while at the same time assessing ways to quantitatively identify replacement processes in diachronic linguistics.

Genomic Evidence for an African Expansion of Anatomically Modern Humans by a Southern Route

There is general agreement among scientists about a recent (less than 200,000 yrs ago) African origin of anatomically modern humans, whereas there is still uncertainty about whether, and to what extent, they admixed with archaic populations, which thus may have contributed to the modern populations’ gene pools. Data on cranial morphology have been interpreted as suggesting that, before the main expansion from Africa through the Near East, anatomically modern humans may also have taken a Southern route from the Horn of Africa through the Arabian peninsula to India, Melanesia and Australia, about 100,000 yrs ago. This view was recently supported by archaeological findings demonstrating human presence in Eastern Arabia >90,000 yrs ago. In this study we analyzed genetic variation at 111,197 nuclear SNPs in nine populations (Kurumba, Chenchu, Kamsali, Madiga, Mala, Irula, Dalit, Chinese, Japanese), chosen because their genealogical relationships are expected to differ under the alternative models of expansion (single vs. multiple dispersals). We calculated correlations between genomic distances, and geographic distances estimated under the alternative assumptions of a single dispersal, or multiple dispersals, and found a significantly stronger association for the multiple dispersal model. If confirmed, this result would cast doubts on the possibility that some non-African populations (i.e., those whose ancestors expanded through the Southern route) may have had any contacts with Neandertals.

Genomic evidence for an African expansion of anatomically modern humans by a Southern route.

There is general agreement among scientists about a recent (less than 200,000 yrs ago) African origin of anatomically modern humans, whereas there is still uncertainty about whether, and to what extent, they admixed with archaic populations, which thus may have contributed to the modern populations' gene pools. Data on cranial morphology have been interpreted as suggesting that, before the main expansion from Africa through the Near East, anatomically modern humans may also have taken a Southern route from the Horn of Africa through the Arabian peninsula to India, Melanesia and Australia, about 100,000 yrs ago. This view was recently supported by archaeological findings demonstrating human presence in Eastern Arabia >90,000 yrs ago. In this study we analyzed genetic variation at 111,197 nuclear SNPs in nine populations (Kurumba, Chenchu, Kamsali, Madiga, Mala, Irula, Dalit, Chinese, Japanese), chosen because their genealogical relationships are expected to differ under the alternative models of expansion (single vs. multiple dispersals). We calculated correlations between genomic distances, and geographic distances estimated under the alternative assumptions of a single dispersal, or multiple dispersals, and found a significantly stronger association for the multiple dispersal model. If confirmed, this result would cast doubts on the possibility that some non-African populations (i.e., those whose ancestors expanded through the Southern route) may have had any contacts with Neandertals.

Back to Africa: Second Chances for the Children of West African Immigrants

This paper examines phenomenon of West African parents living in Europe and North America who send their older children back home: from places of high immigrant aspiration to those of hardship and privation. Drawing on a project on West African immigration to Europe and on previous field studies in Africa, we conclude that West African immigrants fearing consequences of their children's indiscipline in where racism and hostility can endanger entire family, may send unruly children back to home country. In doing so, we believe, they build on long-standing African disciplinary efforts in hopes of toughening their children's resilience to challenges in new place and wait for risk to dissipate. Key Words: African families, cross-cultural, culture/race/ethnicity, ethnography, fostering, migration. Recent decades have seen a sharp rise in number of West African nationals in Europe and North America. Most have been young men seeking work or a degree, though women have come in greater numbers as well, whether independently or, under family reunification provisions, to join a husband (Sow, in press). More thinly documented have been West African children who are directly affected by international migration to West. Some of these children are left behind when a parent travels abroad for work; others come as migrants themselves, whether as dependents of a working parent or, in more extreme cases, unaccompanied by an adult. Among most puzzling cases are those of children of West African immigrants in Europe or North America who are sent back to Africa, particularly children of older school age. Leaving places that seem to offer every advantage - established health and educational systems as well as likelihood of a stable, prosperous future - these children effectively return to countries with levels of personal hardship and privation that most Europeans and Americans would find unacceptable for their own children (Aries, 1962). When asked to explain their actions, immigrant parents may point to lower costs of living and abundant child care back home. Alternatively, they may declare that a child is adapting poorly to new place or needs to grow up knowing family's ancestral roots. If pressed, though, nearly all West African immigrant parents living in Europe and United States, which we describe collectively as the West, ultimately say they want their children to gain a secure footing West. Observations like these raise two questions. First, what might immigrants of recent West African origin find so objectionable about countries usually described as pinnacles of African immigrant ambition to point that they would send their children back to live in one of poorest regions on earth? Second, why would they so often send their children back home at just point when children should be preparing most intensively for a successful professional life in their new homes? Stripped of their wider social and cultural contexts, we believe apparent facts in this case are misleading. Drawing from our past and present studies in Africa and Europe and from a range of secondary sources, we examine in some detail West African tenet that ensuring a child's social and intellectual development requires maximal parental access to long-standing disciplinary practices. We then turn to two related concerns of West African parents about life in Europe and United States. One is what parents see as a Western tendency to coddle and spoil children and to restrict parents' access to discipline they may deem necessary for bringing a child into line. A child with an easy life, they fear, will have faltering interest in school and career achievement, losing ambitions parents had for him or her, quite possibly main reason they made international move in first place. Even more serious for parents may be repercussions of an undisciplined child's involvement in gangs, violence, and crime. …

Intercruzamento de humanos modernos com neandertais: novas perspectivas à luz da genética

Some fossil analyses have found osteological similarities between modern humans and Neanderthals that suggest that there was interbreeding between the two species. If, however, we accept the recent African replacement hypothesis, under which modern humans replaced Neanderthals in Europe without interbreeding of the two groups, then these traits could belong to a common ancestor of the two species or maybe could represent an example of convergent evolution. Over a decade of mitochondrial DNA studies, it has been established that, for this molecule, modern humans and Neanderthals are clearly separate genetic lineages, without signs of interbreeding. The recent finding that modern humans and Neanderthals share significant portions of their nuclear DNA, however, raises new questions about the Out-of-Africa hypothesis and about what makes us modern humans.

Growth and diffusion of e‐journal usage in universities of the western Himalayan region of India

PurposeThe purpose of this paper is to study and analyse the information communication technology‐based growth and diffusion of research using e‐journals for two universities belonging to different states in the western Himalayan region of India.Design/methodology/approachThe paper uses an assessment period for the analysis of usage of e‐journals of 36 months from 2007‐2009. It demonstrates a relative comparison of the usage of e‐journals within the framework of a logistic model and the S‐curve. In the process, the status of internet users, from international level to national and university level, is also analysed.FindingsOwing to the rapid technological growth and its phase‐wise development, the “Replacement hypothesis” does not permit the expectation of a smoother behaviour in the cumulative growth in internet users and consequently the usage of e‐journals in these universities. A simple statistical analysis of the usage was also undertaken. The coefficient of variation shows a wide fluctuation for four out of 12 publishing houses. Compound growth rate was also calculated and analysed for the two universities. A typical case of usage of e‐journals from one publishing house was also analysed more thoroughly with a likely future projection.Research limitations/implicationsThis analysis reflects the limitations inherent in the logistic model, particularly the linear growth rate and the appearance of the inflection point at Xs/2 in the S‐curve.Originality/valueThe paper presents an in‐depth analysis of growth and diffusion of usage of e‐journals in two universities located in the western Himalayan region of India, for the first time. It also projects the usage of e‐journals, reflecting research progress, until the time of saturation in the S‐curve of each of the universities in the region.

The society of our “out of Africa” ancestors (I)

The “out of Africa” hypothesis proposes that a small group of Homo sapiens left Africa 80,000 years ago, spreading the mitochondrial haplotype L3 throughout the Earth.1-10 Little effort has been made to try to reconstruct the society and culture of the tribe that left Africa to populate the rest of the world.1 Here, I find that hunter-gatherers that belong to mitochondrial haplotypes L0, L1 and L2 do not have a culture of ritualized fights. In contrast to this, almost all L3 derived hunter-gatherers have a more belligerent culture that includes ritualized fights such as wrestling, stick fights or headhunting expeditions. This appears to be independent of their environment because ritualized fights occur in all climates, from the tropics to the arctic. There is also a correlation between mitochondrial haplotypes and warfare propensity or the use of murder and suicide to resolve conflicts. The data implicate that the original human population outside Africa is descended from only two closely related sub-branches that practiced ritual fighting and had a higher propensity towards warfare and the use of murder for conflict resolution. This warfare culture may have given the out of Africa migrants a competitive advantage to colonize the world. But it could also have crucially influenced the subsequent history of The Earth. In the future, it would be interesting to see how we could further reconstruct the society and culture of the “Out of Africa Tribe.”

Molecular Modeling of Membrane Interactions with Trehalose - A Molecular View on the Water Replacement Hypothesis

Lipid Bilayers are the fundamental scaffold representing cell membranes. In order to understand cell interactions with the environment we need to understand lipid bilayer interactions. Here we are presenting effects of the low molecular weight sugar trehalose on lipid bilayers in the hydrated and dry state. We show by detailed simulations that trehalose can significantly alleviate dehydration injury in bilayer stacks as well as in single bilayers. To simulate the latter we needed to develop a way to suppress the interactions of bilayers under periodic boundary conditions. A main effect is the change of the hydrogen bonding network and the membrane electric potential under dehydration with and without sugars. The state of the membrane under dehydration with sugars is in area per molecule (fluidity) similar to a free bilayer. However, structural properties are significantly altered.

<i>From Cameroon to Paris: Mousgoum Architecture in and out of Africa</i> (review)

<i>From Cameroon to Paris: Mousgoum Architecture in and out of Africa</i> (review)

New Orleans Music as a Circulatory System

essay provides a roughly chronological history of a single musical tradition in New Orleans, the brass band parade, as a case study that supports a more expansive proposition. The first half of this proposition is specific to New Orleans: I note that the city has become largely identified with African American musical practices and repertoires and, further, that the associations between music, race, and place can be adequately subsumed under the categorical term New Orleans Music. While New Orleans Music includes an amorphous collection of interrelated styles--brass band, jazz, blues, rhythm & blues, soul, and funk, to name the most prevalent--they are bound together through an association with race (African American), place (New Orleans), and functionality (social dance) to such a degree that even a disaster of immeasurable consequences, which disproportionately affected that race and dislocated them from that place, has not threatened its cohesiveness. The consensus about the overall attributes of New Orleans Music is so pervasive that naming them as such seems redundant. The second half of the proposition raises a more sweeping question: By what processes do specific musical forms and practices become linked to particular people and places? essay pursues the role of discourse and media--including eyewitness accounts, historical and musicological studies, musicians' autobiographies, fictional writings, media reports, images, films, and sound recordings--in solidifying the connections between people, places, and musical traditions. New Orleans Music is broadly synonymous with African American music, but this affiliation is by no means timeless and was facilitated, in part, by the writing of jazz history since the 1930s. The claim made most resoundingly in the book Jazzmen (1939) that jazz began just [in New Orleans], not somewhere else (Ramsey and Smith 1939, 5) changed the characterization of New Orleans as a musical city, altering understandings not only of where jazz came from but what constitutes the entirety of New Orleans Music. Prior to being nominated the birthplace of jazz, New Orleans's musical reputation was based on a multitude of offerings, including ballroom dance and French opera, street criers and organ grinders (Kmen 1966). The marching bands that led parades and funerals with music represented numerous ethnicities and races, but as jazz emerged in the first decades of the twentieth century, African Americans, mixed-race Creoles, and European Americans reconfigured the brass band as a black music ensemble, performing syncopated and improvised dance music in burial processions that came to be called jazz funerals and in community parades known as second lines (Schafer 1977; White 2001). These parades wound through an extraordinarily heterogeneous urban center, led by a diverse set of musicians that embodied the city's complex history of interaction, but in narratives of jazz and New Orleans Music they are often narrowly presented as a strictly African American phenomenon. More precisely, jazz funerals and second line parades have been reimagined as a conduit that links jazz back to the celebrated slave dances at Congo Square and, by implication, to A representative example can be drawn from the television documentary Jazz Parades: Feet Don't Fail Me Now (1990) directed by folklorist Alan Lomax near the end of his career. In the opening sequence, we are shown a community procession called a second line parade, with African Americans dancing through the streets while the Dirty Dozen Brass Band plays their original song My Feet Can't Fail Me Now. This isn't chaos, Lomax narrates. It's black tradition right out of Africa. In an arresting scene, footage of black New Orleanians is intercut with various archival clips of ritual and folkloric dancing in West As Lomax discusses the intimate relation between music and bodily movement and points out similarities between specific dance steps, he states what cannot have escaped the observation of any attentive viewer: Below the surface runs the deep tide of African tradition. …

Application of Hypothesis of Replacement at the Analysis of a Slow Flow of a Body by a Viscous Fluid

On the basis of hypothesis of replacement and the vector formula of Newton’s law for a viscous fluid the way of a finding of resistance a slow flow by an incompressible fluid of bodies of the various form is represented. Application of an offered way to calculation of a flow of various bodies is shown: a sphere, a cylinder, a oblong ellipsoid, a flat plate. Comparison with results of other authors is given.

In search for the determinants of share repurchases policies in the Italian equity capital market: An event study

In the last decade the number of buyback transactions involving listed companies in the Italian equity capital market has experienced a huge growth. However, no clear understanding of this phenomenon has yet been reached, also because of the limited information available on such financial decisions. The purpose of this paper is to check the main hypotheses behind the determinants of share repurchases, analysing the effect of own share buyback announcements specifically on the performance of the listed companies before and after the discontinuity introduced in Italy through the Reform of the financial markets. The first major outcome coming from the empirical analysis deals with the strong incentive played by the reform mentioned above, which introduced stricter corporate governance criteria, leading to a sharp increase in the volume and frequency of share buyback announcements, as well as in the number of companies getting access to this instrument. Secondly, the analysis strongly supports the replacement hypothesis theory, which states that buybacks have become a better substitute for dividends as a remuneration policy for shareholders.

Out of Africa and into epigenetics: discovering reprogramming drugs

Out of Africa and into epigenetics: discovering reprogramming drugs

Starved for Science: How Biotechnology Is Being Kept Out of Africa – By Robert Paarlberg

Starved for Science: How Biotechnology Is Being Kept Out of Africa – By Robert Paarlberg