African populations and the evolution of human mitochondrial DNA.

The proposal that all mitochondrial DNA (mtDNA) types in contemporary humans stem from a common ancestor present in an African population some 200,000 years ago has attracted much attention. To study this proposal further, two hypervariable segments of mtDNA were sequenced from 189 people of diverse geographic origin, including 121 native Africans. Geographic specificity was observed in that identical mtDNA types are shared within but not between populations. A tree relating these mtDNA sequences to one another and to a chimpanzee sequence has many deep branches leading exclusively to African mtDNAs. An African origin for human mtDNA is supported by two statistical tests. With the use of the chimpanzee and human sequences to calibrate the rate of mtDNA evolution, the age of the common human mtDNA ancestor is placed between 166,000 and 249,000 years. These results thus support and extend the African origin hypothesis of human mtDNA evolution.     

Dating and context of rock engravings in southern Africa

Rock art is seldom recovered from sealed archeological contexts and is therefore difficult to date or integrate with other artifactual assemblages. South African engravings, found on low rocks at open-air sites, exemplify the problem. Multiscale spatial study of technique, thematic variation, faunal content, geoarcheological paterning, settlement history, and ethno-archeological setting provides coherent information on environment, time, and group identity. The major periods of naturalistic animal engravings coincide with wetter and warmer climates abot 3200 to 2500 and 2250 to 1800 years before present, but the earliest engravings may be older than 4000 years. Geometric designs were favored after 1300 years before present, when climate was drier and when one identity-conscious population of Bushman engravers first encountered domesticated animals.     

The ecology of early man in southern Africa

It is not possible at present to demonstrate hominid occupation of southern Africa prior to the middle or late Pliocene, perhaps 3 million years ago. It may be the case that much, if not most, of the subcontinent was in fact uninhabited before that. The earliest hominid known to have lived in southern Africa is Australopithecus africanus. It was apparently replaced by Homo (?evolved into Homo) by 2 million years ago, at approximately the same time as A. robustus is first recorded locally. Homo and A. robustus then coexisted until perhaps 1 million years ago, after which Homo survived alone. There is no solid evidence that either of the southern African australopithecines made tools or accumulated bones. In fact, at the known sites, it now seems more likely that the bones, including those of the australopithecines themselves, were accumulated by carnivores. The known archeological record of southern Africa begins 2 million to 1.5 million years ago and the oldest stone tools may belong to the Oldowan Industry. Far better documentation exists for the succeeding Acheulean Industrial Complex, which was present in southern Africa almost certainly before 1 million years ago and persisted with modifications probably until sometime between 300,000 and 130,000 years ago. Although it is known that Acheulean peoples made handaxes, cleavers, and other stone tools, very little else is known about the activities of Acheuleans in southern Africa. Far more is known about their Middle and Later Stone Age successors. Southern African MSA peoples were perhaps among the earliest anywhere to take systematic advantage of aquatic resources for their subsistence, although they apparently did so far less effectively than did the LSA peoples who followed them. There are also contrasts between the ways in which MSA and LSA peoples dealt with terrestrial prey and between the contents of MSA and LSA artifact assemblages. The LSA peoples, for example, seem to have made much more extensive use of bone as a raw material, and they were the first to manufacture articles that are clearly interpretable as ornaments or art objects. From an evolutionary perspective, the LSA may represent a quantum advance over the MSA, perhaps correlated with the replacement of an archaic human physical type by the modem one. However, this must remain only a working hypothesis until much more is learned about the earliest LSA, dating to 35,000 to 40,000 years ago or more, and until there are adequate samples of well-provenienced MSA and early LSA physical remains. The later LSA, postdating 20,000 to 18,000 years ago, is reasonably well known. Later LSA peoples were probably at least partly responsible for the extinction of several large mammals in southern Africa about 10,000 years ago. By that date or shortly thereafter, at least some LSA peoples established basic hunting-gathering adaptations, which continued until the introduction and spread of agriculture and pastoralism, beginning roughly 2000 years ago. Thereafter, hunters and gatherers became progressively restricted in numbers and distribution, such that today only a very few exist, restricted to some of the most marginal environments of the subcontinent. It remains a major goal of southern African archeology to shed more light on the evolution and operation of hunting-gathering cultures during the vast time span when they covered all of southern Africa.     

Ages for the Middle Stone Age of southern Africa: implications for human behavior and dispersal

The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa-the Still Bay and Howieson's Poort industries-that are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies. We report ages for nine sites from varied climatic and ecological zones across southern Africa that show that both industries were short-lived (5000 years or less), separated by about 7000 years, and coeval with genetic estimates of population expansion and exit times. Comparison with climatic records shows that these bursts of innovative behavior cannot be explained by environmental factors alone.     

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...     

A high-resolution paleoclimate record spanning the past 25,000 years in southern East Africa

High-resolution profiles of the mass accumulation rate of biogenic silica and other geochemical proxies in two piston cores from northern Lake Malawi provide a climate signal for this part of tropical Africa spanning the past 25,000 years. The biogenic silica mass accumulation rate was low during the relatively dry late Pleistocene, when the river flux of silica to the lake was suppressed. Millennial-scale fluctuations, due to upwelling intensity, in the late Pleistocene climate of the Lake Malawi basin appear to have been closely linked to the Northern Hemisphere climate until 11 thousand years ago. Relatively cold conditions in the Northern Hemisphere coincided with more frequent north winds over the Malawi basin, perhaps resulting from a more southward migration of the Intertropical Convergence Zone.     

家蝇原种群的建立及其性状初步测定

通过引进和收集家蝇原种群素材28份,采用分离选育,同质组群繁育措施,培育了4个表型性状基本稳定一致的原种群。4个原种群采用保种繁育,每个世代在蛹期、成虫期适度外形选择,在幼虫期强化营养与培育。经测定,其中A、B两群培育26世代每对成蝇产卵量分别达490、460粒,群体平均寿命22 d,产卵量比原始种群提高1倍。C、D两群培育22世代,每对成蝇产卵量为420、503粒,群体平均寿命亦达22 d,产卵量比原始种群提高80%。     

非洲小农经济状况与我国援非农业技术示范中心对策

分析影响非洲小农收入的主要因素,非洲粮食作物种植状况,非洲农用土地状况及非洲农业政策状况,指出援非农业技术示范中心的优势与劣势,并提出相应的对策。     

Ecology and acculturation among native peoples of central Brazil

Simple exposure to Western goods may not be a sufficient explanation of why isolated village communities increase their participation in external market economies. The degree of market participation by four native villages in central Brazil is related to the difficulty of making a living from slash-and-burn subsistence agriculture as measured by the ratio of labor input to food output.     

中国南方绿豆新品种及高产配套栽培技术

绿豆是一种抗逆性很强的作物,生育期短、播期弹性大、适应性广,利于用地、养地,而且经济效益较高,深受农户喜爱.     

The southern route "out of Africa": evidence for an early expansion of modern humans into Arabia

The timing of the dispersal of anatomically modern humans (AMH) out of Africa is a fundamental question in human evolutionary studies. Existing data suggest a rapid coastal exodus via the Indian Ocean rim around 60,000 years ago. We present evidence from Jebel Faya, United Arab Emirates, demonstrating human presence in eastern Arabia during the last interglacial. The tool kit found at Jebel Faya has affinities to the late Middle Stone Age in northeast Africa, indicating that technological innovation was not necessary to facilitate migration into Arabia. Instead, we propose that low eustatic sea level and increased rainfall during the transition between marine isotope stages 6 and 5 allowed humans to populate Arabia. This evidence implies that AMH may have been present in South Asia before the Toba eruption.     

Foods from cassava and their relevance to Nigeria and other African countries

The need for an indigenous croplocally grown by subsistence farmers that willhelp bring direct economic benefits to thosewho need it most is very important. Cassava hasa great potential for this purpose if certainproblems are solved, because cassava has playedvital roles in the diet of many Africancountries especially the grassroot people, yetthe utilization of the crop in diversifiedforms has been very limited. There are few foodproducts from cassava that are processedindustrially with added value that will be ofhigher nutritional value and have longer shelflives. There are a number of traditionallyprocessed staple foods from cassava in Nigeriaand other African countries that needimprovement. Most of these foods can beimproved on if the market for them is assuredby the end users, a market that is currentlylacking. It will be necessary to create morepublic awareness within Nigeria and otherAfrican societies to increase the acceptabilityof such novel products and this requires amultidisciplinary approach to interpret whatscientists and technologists are doing to theold crop in the present age.     

陕南卷丹10个野生种群数量性状变异分析

为揭示陕南地区卷丹Lilium lancifolium野生种群的表型变异程度和规律, 以该区10个有代表性的卷丹野生种群, 每个种群30个个体为试材, 对其茎、叶、花的茎粗、叶片数、着花量等16个数量性状指标进行方差分析、相关性分析及聚类分析, 探讨种群间及种群内表型多样性的变异特点。结果表明:①卷丹数量性状在种群间和种群内均存在一定程度的变异, 不同性状的平均变异系数为2.07%(花丝长)~35.38%(着花量), 种群间的平均变异系数为7.52%(汉台区天台山乡种群)~17.18%(城固县石槽河乡种群)。②相关性分析表明, 着花量(r=0.684, P < 0.05, n=10), 外瓣宽长比(r=0.651, P < 0.05, n=10), 柱头宽(r=0.729, P < 0.05, n=10)与海拔高度有显著正相关性, 中部叶宽长比(r=-0.743, P < 0.05, n=10), 花丝长(r=-0.795, P < 0.01, n=10)与海拔高度有显著负相关性; 且茎秆高度(r=0.733, P < 0.01, n=10), 叶片数(r=0.718, P < 0.01, n=10), 着花量(r=0.752, P < 0.01, n=10)与生境有显著正相关性, 上部叶宽长比(r=-0.707, P < 0.05, n=10), 内瓣宽长比(r=-0.681, P < 0.05, n=10)与生境有显著负相关性; ③Q聚类分析显示, 陕南地区10个卷丹野生种群可以初步分为2组, 汉台区天台山乡种群单独为一组。     

豫南地区珍稀濒危药用植物及其保护利用

根据《中国植物红皮书》《国家重点保护野生植物名录(第一批)》及《濒危野生动植物种国际贸易公约》统计,豫南地区共有珍稀濒危药用植物44种,隶属于26科37属,其中国家重点保护的有23种。     

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.     

滇南乡土地被植物资源及在园林中的应用

滇南的西双版纳作为"热带种质资源基因库",具有丰富的乡土地被植物资源.通过文献调查和野外考察,共收载滇南乡土地被植物资源56科134属205种,评价并分析其分布、生境及观赏特性.推荐其中3种(链荚豆Alysicarpus vaginalis,穗序木兰Indigofera spicata和地石榴Ficus tikoua)在热带、亚热带园林绿化中应用,并对滇南乡土地被植物资源的可持续发展进行讨论.表2参17