马尔萨斯"警醒"与中国人口的国家干预政策

1958～1979我国明显处于马尔萨斯"诅咒"或"陷阱"时期,谷底在1960年.1949年以来的实践证明"警醒"或"陷阱"最主要作用是促进"政府干预"性质的"基本国策(计划生育)"的诞生和实施.本文利用总和生育率(TFR)模型P n =(TFR/ 2)P n-1计算了如果"不实行"计划生育政策,从1949年起政策支持T...     

Reawakening Malthus: empirical support for the Smail scenario

Editor's Note: In the November issue of the Journal, Kenneth Smail presented the third and final part of his series on Malthus and human population growth. Here, Jeffrey McKee offers additional thoughts on population and its impact on biodiversity and extinction history. Am J Phys Anthropol 122: 371–374, 2003. © 2003 Wiley‐Liss, Inc.     

The global dynamics of a discrete nonlinear hierarchical population system

This paper is concerned with the global dynamics of a hierarchical population model,in which the fertility of an individual depends on the total number of higher-ranking members.We investigate the stability of equilibria,nonexistence of periodic orbits and the persistence of the population by means of eigenvalues,Lyapunov function,and several results in discrete dynamical systems.Our work demonstrates that the reproductive number governs the evolution of the population.Besides the theoretical results,some numerical experiments are also presented.     

The effects of global warming on Daphnia spp. population dynamics: a review

Various species of Daphnia usually play a key role in the food web of temperate freshwater systems. There is much evidence to show that climate change may influence Daphnia population dynamics, consequently altering both predator–prey interactions and the efficiency of algal biomass control in these ecosystems. This review will analyse and discuss the current knowledge on Daphnia responses to climate warming based on an analysis of selected papers. The presented results indicate that warming may have important direct and indirect effects on Daphnia biology and ecology via its influence on their life-history processes (metabolism, growth, reproduction) and the properties of their habitats. The plasticity of daphnids in terms of adaptive responses is generally high and includes phenotypic adaptations and changes in genotypes, although it also depends upon the strength of selection and the available genetic variation. The seasonal timing and magnitude of temperature increases are important for seasonal biomass fluctuations of Daphnia and similarly influence the potential synchrony of daphnids and phytoplankton succession (the timing hypothesis). In light of the most recent studies on this topic, even a minor warming during short but critical seasonal periods can cause factors that disturb Daphnia population dynamics to coincide, which may destabilize lake food webs by decoupling trophic interactions. Both winter and spring are important critical periods for determining future seasonal fluxes of Daphnia spp. and, consequently, the time of the clear-water phase and the occurrence and duration of Daphnia midsummer decline. Winter conditions may also affect the impact of fish predation on daphnids during summer months. However, the effects of global warming on Daphnia population dynamics and on ecosystem functioning are often difficult to predict due to their complexity and the presence of both antagonistic and synergistic drivers. Thus, the diverse responses of daphnids to climate anomalies depend on both biotic (predator abundance and seasonal phytoplankton succession) and abiotic factors (e.g. hydrodynamics, intensity and duration of thermal stratification, trophic state or geomorphology) of lakes, which are directly influenced by weather changes. The analysis and quantification of such complex interactions require the involvement of different kinds of specialists and the development of accurate research approaches, such as molecular genetic methods or mathematical modelling.     

Historical dynamics of a declining wolf population: persecution vs. prey reduction

Using records from archives detailing bounties for wolves killed in northern Spain during the eighteenth and nineteenth centuries, we investigated demographic and spatial distribution parameters of the population to determine whether direct persecution or prey availability was responsible for the observed population decline. Captures of adult, subadult, and young individuals, including those of litters, showed a downward trend. Progressive decreases in age ratio and litter size, and the increase in the proportion of males, were compatible with a population under food stress, driven by the extinction of wild ungulates, the sharp reduction in livestock numbers, and the lack of alternative prey. The immigration and dispersal process does not seem to have functioned under such conditions. In the study area, where strychnine was not used until the end of the nineteenth century, the broadly accepted idea of human persecution having an exclusive or primary role in wolf decline does not necessarily apply.     

Feedbacks, thresholds and synergies in global change: population as a dynamic factor

The role of feedbacks, thresholds, and synergies in environmental science, and their implications for environmental degradation under a growing human population, are reviewed. A detailed analysis of the impacts of climate change on water resources is used to elucidate mechanisms by which nonlinearities arise in environmental science. Additional examples are drawn from analysis of soil degradation and non-climate related degradation of water resources. The often-assumed notion that impacts will grow in proportion to population size is shown to be overly optimistic. In particular, feedbacks, thresholds, and synergies among multiple threats, tend to amplify risk and cause environmental impacts to grow considerably faster than linearly in population size, even when the per-capita living standard and the technological systems deployed to achieve that living standard are assumed to remain constant.     

Lipreading: Remembering Saartjie Baartman

This paper moves towards a retracing of an imagined ‘metanarrative’ on race and gender in emergent sciences of human difference. It is a specific bid to locate a series of ideas on transcendent notions of objectivity in one of their sites of practice and gestures to contemporary practices of defining difference. In 1810 Saartjie Baartman, a !Kung woman from South Africa, was taken to England for public display as the ‘Hottentot Venus’. Amidst contention on the colonization of the Cape and the moral and social capacities of Africans to progress to civility, Saartjie Baartman's differences were evaluated in relation to European senses of self. This paper examines a court case on the issue of Saartjie Baartman's consent to such an exhibition, and upon her death, an autopsy report by the comparative anatomist Cuvier on her capacity to reason according to emergent racial criteria. As these legal, bio-medical and anthropological discourses on non-European difference gained strength in the nineteenth century new categories of difference were constructed and reified as race. As the moral core of the person became increasingly bound to biology the compelling difference of Saartjie Baartman fixated on her sexual self. Signified in her genitalia, her sexuality was devalued as excessive and abhorrent to normative and masculine European self representations. By such a process the sexual difference of ‘Hottentot’ women came to signify a form of racialized difference so extreme as to create a new, and devalued racial type.     

Test for a population expansion after a drastic reduction in population size using DNA sequence data

Populations may, during their evolutionary history, go through drastic changes in population size due to bottlenecks or founder events upon colonization of new areas. This involves a subsample of haplotypes, causing the allele frequencies to be different from the original population. In addition, the period of recovery after a bottleneck can be of considerable length. If reproduction is unequal among individuals but random with regard to haplotype, large deviations from the patterns expected in a stable population may result. By means of computer simulation, I have analysed the patterns arising when populations undergo bottlenecks and then slowly recover, and used two new statistical tests for the detection of the bottleneck. A test based on the variance of the relative frequency of haplotypes had generally high power even at low sample size (n=25). This statistic was most powerful after very strong bottlenecks and lost power with increasing propagule size. A test based on the variance of the pairwise differences shows slightly less power. As expected, power was reduced when migration into the founder population was allowed from the source population. This suggests that the test is particularly suited for detecting relatively recent and strong bottlenecks, and thus may be a valuable tool for identifying population events on a fine temporal scale, such as colonisations after the last glaciation.     

Discrete three-stage population model: persistence and global stability results

A general three-stage discrete-time population model is studied. The inherent net reproductive number for this model is derived. Global stability of the origin is established provided that the inherent net reproductive number is less than one. If it is larger than one the existence of a unique positive fixed point is proved and the persistence of the system is established. Finally, for certain parameter ranges global stability of the positive fixed point is proved.