Fossil soils and grasses of a middle miocene East african grassland

Fossil soils and grasses from the well-known Miocene mammal locality of Fort Ternan, southwestern Kenya, are evidence of a mosaic of grassy woodland and wooded grassland some 14 million years ago. This most ancient wooded grassland yet known on the African continent supported more abundant and diverse antelopes than known earlier in Africa. Ape fossils at Fort Ternan, including Kenyapithecus wickeri, were associated with woodland parts of the vegetation mosaic revealed by paleosols. Grassland habitats were available in East Africa long before the evolutionary divergence of apes and humans some 5 to 10 million years ago.     

Ecological security evaluation of Africa

Africa, the second largest continent in the world, has achieved remarkable economic and political results through exploration and positive development. Ecological security comprehensively reflects the health and integrity of an ecosystem, and it is broadly defined as the security state of a complex artificial ecosystem composed of natural, economic and social factors. Ecological security determines the potential for sustainable development in Africa, especially with its rapidly developing economies. However, there is a lack of information on the ecological security state of the continent as a whole. In this study, we constructed an evaluation system based on a pressure-state-response model and evaluated the ecological security state of all 54 African countries. The results showed that, at the national level, the ecological security state of the countries in Africa differed, as did their spatial and temporal variations from 1995 to 2016. In general, African countries showed relatively good ecological security. The years 2007 and 2001 were the worst and best years, respectively, in terms of ecological security during the study period. At the regional level, North Africa and West Africa had the best and worst ecological security, respectively.     

Sustainable intensification of agriculture in Africa

Sustainable intensification is a key component of agricultural development in Africa, urgently needed to wean the continent off foreign food supply and to limit agricultural farmland expansion. It is expected that a relatively small fraction of farmers will adopt fertilizer technology, as profits in current economic settings are relatively small while risks are considerable with varying prices and uncertain yield responses. Many smallholders depend on off-farm income and local markets for food supply. Structural adjustments are therefore needed to allow management of larger units of land by trained farmers willing to take this opportunity, while recognizing land right sensitivities. There are large opportunities for African commodity crops to improve food security, including cassava and East African highland banana that strongly respond to fertilizer with limited environmental risks under good management. This requires investments in better functioning markets, local fertilizer production facilities that can produce regional crop blends and cost-efficient distribution networks, providing balanced fertilizers for African farmers.     

Signatures of positive selection for local adaptation of African native cattle populations: A review

Cattle are central to the lives and diverse cultures of African people. It has played a crucial role in providing valuable protein for billions of households and sources of income and employment for producers and other actors in the livestock value chains. The long-term natural selection of African cattle typically signals signatures in the genome, contributes to high genetic differentiations across breeds. This has enabled them to develop unique adaptive traits to cope with inadequate feed supp...     

20世纪80年代中期全球变暖前后亚非夏季风特征分析

该文针对全球温度场在20世纪80年代全球明显的突然变暖事件,研究了变暖前后全球温度场和降水场的时空分布特征,以及相应季风环流圈的变化特征,并且与20世纪60年代全球变冷气候事件作了对比分析.结果表明,变暖后全球大范围增温,增温地区包括欧亚大陆大部、非洲地区大部和印度洋南部.与此同时,全球降水场也有明显的变化.1990—1995年与1980—1985年相比较,中国华北地区大部分地区、印度中南部和北非Sahel大部分地区夏季总降水量有所回升,而中国华北地区南部地区和印度北部地区降水有所减少.对比分析80年代变暖前后气候环流场,发现非洲夏季风在变暖后有所加强,印度夏季风有所减弱,东亚夏季风强度微弱加强.从海陆热力对比和华北和北非Sahel等地的夏季降水量的小波分析来看,60年代变冷气候事件以年代际信号为主,同位相叠加突出了年代际振荡的作用和强度;而80年代夏季降水量的各时间尺度年代际信号符号相反,相互抵消;与此同时,80年代年际时间尺度的信号较强,起主导作用.所以,80年代气候变暖事件与60年代气候变冷事件相比较,并不是单纯的气候年代际反位相振荡的结果,而是不同时间尺度信号相互作用下引起的气候不同的响应.      

Isolation of a new human retrovirus from West African patients with AIDS

The etiological agent of AIDS, LAV/HTLV-III, is common in Central Africa but is not endemic in other areas of that continent. A novel human retrovirus, distinct from LAV/HTLV-III, has now been isolated from two AIDS patients from West Africa. Partial characterization of this virus revealed that it has biological and morphological properties very similar to LAV but that it differs in some of its antigenic components. Although the core antigens may share some common epitopes, the West African AIDS retrovirus and LAV differ substantially in their envelope glycoproteins. The envelope antigen of the West African virus can be recognized by serum from a macaque with simian AIDS infected by the simian retrovirus termed STLV-IIImac, suggesting that the West African AIDS virus may be more closely related to this simian virus than to LAV. Hybridization experiments with LAV subgenomic probes further established that this new retrovirus, here referred to as LAV-II, is distantly related to LAV and distinct from STLV-IIImac.     

“No one asks for a meal they’ve never eaten.” Or,do African farmers want genetically modified crops?

This article reflects on the relative silence of African farmers within debates around the potential for genetically modified (GM) crops to transform agriculture on the continent. It proposes two strategies for amplifying these voices—one focused on research methodologies, the other on outreach—in order to transform the conversation around GM’s potential in Africa into one that revolves around farmer preferences and priorities.     

Science and Technology Backyard model: implications for sustainable agriculture in Africa

Sustainable food production to feed the growing population in Africa remains a major challenge. Africa has 64% of the global arable land but produces less than 10% of its food locally due to its inherently low soil nutrient concentrations. Poor soil fertility and a lack of fertilizer use are the major constraints to increasing crop yields in Africa. On average only about 8.8 kg NPK fertilizer is applied per hectare by African smallholder farmers. There is therefore considerable potential for increasing food production through sustainable intensification of the cropping systems. The low crop yields in Africa are also partly due to limited farmer access to modern agronomic techniques, including improved crop varieties, a lack of financial resources, and the absence of mechanisms for dissemination of information to smallholders. This study analyzed the Science and Technology Backyards (STBs) model and investigated its use for the transformation of agriculture in Africa. Some key lessons for sustainable crop intensification in Africa can be found from analysis of the STB model which is well established in China. These include (1) scientist-farmer engagement to develop adaptive and innovative technology for sustainable crop production, (2) dissemination of technology by empowering smallholders, especially leading farmers, and (3) the development of an open platform for multiple resource involvement rather than relying on a single mechanism. This review evaluates the benefits of the STB model used in China for adoption to increase agricultural productivity in Africa, with a perspective on sustainable crop intensification on the continent.     

Prospects for control of tick-borne diseases in cattle by immunization in eastern,central, and southern Africa

Tick and tick-borne diseases, especially East Coast fever, caused byTheileria parva, are amongst the most important factors limiting cattle production in Eastern, Central, and Southern Africa. In the past, they have been controlled mainly by the use of acaricides to kill ticks. Immunization has been shown to be an effective alternative method of control of tick-borne diseases in limited field trials. A development program has been initiated to produce vaccines and implement immunization on a wide scale in the region in a sustainable manner as part of an integrated tick and tickborne disease control program. The consequent reduction in cattle mortality is expected to have far-reaching benefits for the region.     

Toward sustainable intensification of agriculture in sub-Saharan Africa

Across the African continent efforts to intensify agriculture have been limited to specific commodities, locations or particular production schemes. The causes for the widespread failure to overcome low land and labor productivity while maintaining ecosystem services have often be analyzed but remain poorly understood. A social-ecological system approach may help to better understand the complex nature of ecological disadvantages, postcolonial structures, limited connect between producers and consumer markets, low off-farm livelihood opportunities, partial underpopulation and lacking experience with the concept of sustainable production as a major impediment for sustainable intensification of the agricultural sector. Nevertheless, recent success stories in agro-pastoral systems as well as urban vegetable and animal production and associated value chains in West Africa, and in intensive mixed-cropping systems of the Great Lakes Region show the potential of stakeholder-driven agricultural intensification. Proper interpretation of these cases may provide lessons for a more widespread eco-intensification of smallholder agriculture in sub-Saharan Africa.     

Phonemic diversity supports a serial founder effect model of language expansion from Africa

Human genetic and phenotypic diversity declines with distance from Africa, as predicted by a serial founder effect in which successive population bottlenecks during range expansion progressively reduce diversity, underpinning support for an African origin of modern humans. Recent work suggests that a similar founder effect may operate on human culture and language. Here I show that the number of phonemes used in a global sample of 504 languages is also clinal and fits a serial founder-effect model of expansion from an inferred origin in Africa. This result, which is not explained by more recent demographic history, local language diversity, or statistical non-independence within language families, points to parallel mechanisms shaping genetic and linguistic diversity and supports an African origin of modern human languages.     

Identifying global centers of genetic diversity for grain sorghum with the use of rice DNA markers

STS and InDel markers developed on the basis of DNA sequences of certain rice genes are used for a comparative study of grain sorghum accessions. The main sorghum genetic diversity centers are revealed, two in Africa and a third in regions of Central, East, and South Asia.     

Complex Shear Wave Velocity Structure Imaged Beneath Africa and Iceland

A model of three-dimensional shear wave velocity variations in the mantle reveals a tilted low velocity anomaly extending from the core-mantle boundary (CMB) region beneath the southeastern Atlantic Ocean into the upper mantle beneath eastern Africa. This anomaly suggests that Cenozoic flood basalt volcanism in the Afar region and active rifting beneath the East African Rift is linked to an extensive thermal anomaly at the CMB more than 45 degrees away. In contrast, a low velocity anomaly beneath Iceland is confined to the upper mantle.     

Cerebral cortices of East african early hominids

An endocast of the frontal lobe of a reconstructed skull, which is approximately 2 million years old, from the Koobi Fora region of Kenya appears to represent the oldest human-like cortical sulcal pattern in the fossil record, while the endocast from another skull from the same region produces an endocast that appears apelike in its frontal lobe and similar to endocasts from earlier South African australopithecines. New analysis of paleoanatomical evidence thus indicates that at least two taxa of early hominids coexisted in East Africa.     

亚非季风区夏季降水与热带东风急流的关系

利用1948～2007年资料,对夏季热带东风急流(TEJ)的结构、亚非季风区夏季降水分布以及TEJ变化与亚非季风区夏季降水的关系进行了研究。结果表明,热带东风急流主要覆盖了热带地区从日界线向西延伸到非洲西海岸的大片地区,其核心位于150～100hPa印度半岛南部10°～15°N,中心风速超过35 m/s;急流中线大致位于70°E,以东是急流的入口区,以西是出口区;在急流的入口区和出口区存在2个近于相反的垂直环流。多年亚非季风区夏季降水分布与热带东风急流的位置和强度有密切关系,在急流不同部位降水特征不同,多雨区主要出现在急流入口区右侧和出口区左侧。热带东风急流与降水分布的关系可以用急流不同部位的垂直速度不同来解释。     

AIDS in Africa: an epidemiologic paradigm

Cases of the acquired immune deficiency syndrome (AIDS) have been reported in countries throughout the world. Initial surveillance studies in Central Africa suggest an annual incidence of AIDS of 550 to 1000 cases per million adults. The male to female ratio of cases is 1:1, with age- and sex-specific rates greater in females less than 30 years of age and greater in males over age 40. Clinically, AIDS in Africans is often characterized by a diarrhea-wasting syndrome, opportunistic infections, such as tuberculosis, cryptococcosis, and cryptosporidiosis, or disseminated Kaposi's sarcoma. From 1 to 18% of healthy blood donors and pregnant women and as many as 27 to 88% of female prostitutes have antibodies to human immunodeficiency virus (HIV). The present annual incidence of infection is approximately 0.75% among the general population of Central and East Africa. The disease is transmitted predominantly by heterosexual activity, parenteral exposure to blood transfusions and unsterilized needles, and perinatally from infected mothers to their newborns, and will continue to spread rapidly where economic and cultural factors favor these modes of transmission. Prevention and control of HIV infection through educational programs and blood bank screening should be an immediate public health priority for all African countries.     

Early origin and recent expansion of Plasmodium falciparum

The emergence of virulent Plasmodium falciparum in Africa within the past 6000 years as a result of a cascade of changes in human behavior and mosquito transmission has recently been hypothesized. Here, we provide genetic evidence for a sudden increase in the African malaria parasite population about 10,000 years ago, followed by migration to other regions on the basis of variation in 100 worldwide mitochondrial DNA sequences. However, both the world and some regional populations appear to be older (50,000 to 100,000 years old), suggesting an earlier wave of migration out of Africa, perhaps during the Pleistocene migration of human beings.     

Genetic evidence for two species of elephant in Africa

Elephants from the tropical forests of Africa are morphologically distinct from savannah or bush elephants. Dart-biopsy samples from 195 free-ranging African elephants in 21 populations were examined for DNA sequence variation in four nuclear genes (1732 base pairs). Phylogenetic distinctions between African forest elephant and savannah elephant populations corresponded to 58% of the difference in the same genes between elephant genera Loxodonta (African) and Elephas (Asian). Large genetic distance, multiple genetically fixed nucleotide site differences, morphological and habitat distinctions, and extremely limited hybridization of gene flow between forest and savannah elephants support the recognition and conservation management of two African species: Loxodonta africana and Loxodonta cyclotis.     

Genetic Differentiation of Different Geographical Populations of Bemisia tabaci （Gennadius） Complex

Bemisia tabaci （Gennadius） is a species complex, which includes different geographical populations with genetic differentiation. The recent progress on the genetic differentiation of various geographical populations of B. tabaci complex was introduced. The genetic differentiation was further analyzed on the basis of the sequences of mtDNA COI and rDNA ITS1 recorded in the world＇s GenBank. Five groups are defined on the basis of mtDNA COI and rDNA ITS1, including the Asia group, America group, Africa group, Australia group, and Biotype B/Mediterranean/Middle East/ Northern Africa/Biotype Ms group. There are several ungrouped geographical classifications, such as the Uganda population, Ivory Coast population, and Taiwan population. Geographical isolation may be the most important factor that contributed to the genetic differentiation of various geographical populations of B. tabaci. Many populations with biological advantages invaded new regions and caused severe economic losses within human activity. It is necessary to strengthen the research of B. tabaci biotype to prevent the spread of invaded populations and the invasion of potentially dangerous populations.     

大风子科的地理分布及其起源

本文以属为单位,将大风子科84个属划分为27个分布亚型,隶属于11个分布类型。在此基础上对本科植物的地理分布进行了分析,认为大风子科是一个典型的热带性质的且富于岛屿区系成分和与各地区联系广泛的类群;其现代分布中心在旧世界热带地区,特别是热带非洲。根据其地理分布分析,结合板块及大陆漂移学说理论,可推断大风子科起源于古南大陆,特别是热带非洲地区;其起源时间至少不迟于白垩纪末期或第三纪初期,这一点已得到了古植物学资料的证实。