Advent and course of pastoralism in the kalahari

It has long been thought that farming and herding were comparatively recent introductions into the Kalahari and that it has been a preserve of foraging "Bushmen" for thousands of years. Agropastoral Bantu-speakers were thought to have entered this region only within the last two centuries. However, fully developed pastoralism and metallurgy are now shown to have been established in the Kalahari from A.D. 500, with extensive grain agriculture and intracontinental trade added by A.D. 800. Archeological, linguistic, and historical evidence delineates the continuation of mixed economies in the region into the present. Consequences of this revised view for anthropological theory and for policy planning concerning contemporary Kalahari peoples are indicated.     

Glacial migrations of plants: island biogeographical evidence

Analyses of the floras of the high north Andean habitat islands (paramos) and the Galápagos Islands show that plant species diversity conforms to the MacArthur and Wilson model of island biogeography but that immigration occurred primarily during glacial periods. Modern plant species diversity is more significantly correlated with area and distance measures of the glacial forms of the islands than with similar measures of the present-day islands.     

蒙古马mtDNA D-loop区遗传多样性与多重母系起源

【目的】对蒙古马mtDNA D-loop区247bp序列进行遗传多样性分析,探讨蒙古马的起源。【方法】采用PCR方法、测序技术及生物信息学方法,将本试验所测得的21匹蒙古马的mtDNA D-loop区序列,与GenBank中公布的43条蒙古马的对应序列,及世界范围内家马、普氏野马和内蒙古地区古马的mtDNA D-loop区序列一起进行系统发育分析。【结果】蒙古马具有39种单倍型,37个多态位点,核苷酸多样度(π)为0.02756±0.00967,单倍型多样度(h)为0.979±0.007,表明蒙古马mtDNA遗传多样性非常丰富。引用世界家马、古马、普氏野马和蒙古马共1074条mtDNA D-loop序列及本研究中21条mtDNA D-loop序列,共同进行系统发育分析,结果显示,蒙古马分布于A、B、C、D、E和F支系。【结论】蒙古马为多重母系起源,且与国内古马的母系起源几乎一致,推测蒙古马可能是中国北方家马的重要母系来源。     

Agricultural origins: centers and noncenters

I propose the theory that agriculture originated independently in three different areas and that, in each case, there was a system composed of a center of origin and a noncenter, in which activities of domestication were dispersed over a span of 5,000 to 10,000 kilometers. One system includes a definable Near East center and a noncenter in Africa; another system includes a North Chinese center and a noncenter in Southeast Asia and the South Pacific; the third system includes a Mesoamerican center and a South American noncenter. There are suggestions that, in each case, the center and noncenter interact with each other. Crops did not necessarily originate in centers (in any conventional concept of the term), nor did agriculture necessarily develop in a geographical "center."     

Arctic air pollution: origins and impacts

Notable warming trends have been observed in the Arctic. Although increased human-induced emissions of long-lived greenhouse gases are certainly the main driving factor, air pollutants, such as aerosols and ozone, are also important. Air pollutants are transported to the Arctic, primarily from Eurasia, leading to high concentrations in winter and spring (Arctic haze). Local ship emissions and summertime boreal forest fires may also be important pollution sources. Aerosols and ozone could be perturbing the radiative budget of the Arctic through processes specific to the region: Absorption of solar radiation by aerosols is enhanced by highly reflective snow and ice surfaces; deposition of light-absorbing aerosols on snow or ice can decrease surface albedo; and tropospheric ozone forcing may also be contributing to warming in this region. Future increases in pollutant emissions locally or in mid-latitudes could further accelerate global warming in the Arctic.     

Traces of human migrations in Helicobacter pylori populations

Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions. These modern populations derive their gene pools from ancestral populations that arose in Africa, Central Asia, and East Asia. Subsequent spread can be attributed to human migratory fluxes such as the prehistoric colonization of Polynesia and the Americas, the neolithic introduction of farming to Europe, the Bantu expansion within Africa, and the slave trade.     

Fossil mammals from baja california: new evidence on early tertiary migrations

Ungulates belonging to the family Barylambdidae were found in the same geologic unit with, but stratigraphically above, a specimen assigned to the Tillodontia and above several molars of the perissodactyl cf. Hyracotherium sp. This arrangement is unusual, as in the well-documented faunas from the Rocky Mountain Region Barylambdidae are known only from the Paleocene, Tillodontia from the Paleocene and Eocene, while Hyracotherium is known only from the Eocene. The expected stratigraphic order would be, from lowest to highest, Barylambdidae, Tillodontia, and Hyracotherium. It is suggested that the Baja California assemblage is late Paleocene on the basis of the generalized molars of cf. Hyracotherium sp. and the characters of cf. Esthonyx sp.     

Interdependence of cell growth and gene expression: origins and consequences

In bacteria, the rate of cell proliferation and the level of gene expression are intimately intertwined. Elucidating these relations is important both for understanding the physiological functions of endogenous genetic circuits and for designing robust synthetic systems. We describe a phenomenological study that reveals intrinsic constraints governing the allocation of resources toward protein synthesis and other aspects of cell growth. A theory incorporating these constraints can accurately predict how cell proliferation and gene expression affect one another, quantitatively accounting for the effect of translation-inhibiting antibiotics on gene expression and the effect of gratuitous protein expression on cell growth. The use of such empirical relations, analogous to phenomenological laws, may facilitate our understanding and manipulation of complex biological systems before underlying regulatory circuits are elucidated.