Random copying,frequency-dependent copying and culture change

Previous evolutionary analyses of human culture have found that a simple model of random copying, analogous to neutral genetic drift, can generate the distinct power-law frequency distribution of cultural traits that is typical of various real-world cultural datasets, such as first names, patent citations and prehistoric pottery types. Here, we use agent-based simulations to explore the effects of frequency-dependent copying (e.g., conformity and anti-conformity) on this power-law distribution. We find that when traits are actively selected on the basis of their frequency, then the power-law distribution is severely disrupted. Conformity generates a “winner-takes-all” distribution in which popular traits dominate, while anti-conformity generates a “humped” distribution in which traits of intermediate frequency are favoured. However, a more passive frequency-dependent “trimming”, in which traits are selectively ignored on the basis of their frequency, generates reasonable approximations to the power-law distribution. This frequency-dependent trimming may therefore be difficult to distinguish from genuine random copying using population-level data alone. Implications for the study of both human and nonhuman culture are discussed.     

Death rates reflect accumulating brain damage in arthropods

We present the results of the first quantitative, whole-lifespan study of the relationship between age-specific neurolipofuscin concentration and natural mortality rate in any organism. In a convenient laboratory animal, the African migratory locust, Locusta migratoria, we find an unusual delayed-onset neurolipofuscin accumulation pattern that is highly correlated with exponentially accelerating age-specific Gompertz-Makeham death rates in both males (r=0.93, p=0.0064) and females (r=0.97, p=0.0052). We then test the conservation of this association by aggregating the locust results with available population-specific data for a range of other terrestrial, freshwater, marine, tropical and temperate arthropods whose longevities span three orders of magnitude. This synthesis shows that the strong association between neurolipofuscin deposition and natural mortality is a phylogenetically and environmentally widespread phenomenon (r=0.96, p < 0.0001). These results highlight neurolipofuscin as a unique and outstanding integral biomarker of ageing. They also offer compelling evidence for the proposal that, in vital organs like the brain, either the accumulation of toxic garbage in the form of lipofuscin itself, or the particular molecular reactions underlying lipofuscinogenesis, including free-radical damage, are the primary events in senescence.     

Abortion rates reflect the optimization of parental investment strategies

Parental investment decisions in human beings, including infanticide, have usually been considered in relation to the postnatal survival probabilities of their children. A number of factors which influence parental ability and willingness to invest in offspring have been identified from these studies. Here we argue that at least some of the same factors which influence investment decisions postpartum also affect the decision to terminate a current pregnancy through voluntary abortion. We show that both female age and marital status influence the probability of abortion, with the key variable being the likelihood of future marriage. Thus, abortion procedures extend a woman's ability to manage her reproduction into the prenatal period.     

Relative growth rates of predator and prey dinosaurs reflect effects of predation

Hadrosaurs grew rapidly, and quantifying their growth is key to understanding life-history interactions between predators and prey during the Late Cretaceous. In this study, we longitudinally sampled a sequence of lines of arrested growth (LAGs) from an essentially full-grown hadrosaur Hypacrosaurus stebingeri (MOR 549). Spatial locations of LAGs in the femoral and tibial transverse sections of MOR 549 were measured and circumferences were calculated. For each bone, a time series of circumference data was fitted to several stochastic, discrete growth models. Our results suggest that the femur and the tibia of this specimen of Hypacrosaurus probably followed a Gompertz curve and that LAGs reportedly missing from early ontogeny were obscured by perimedullary resorption. In this specimen, death occurred at 13 years and took approximately 10-12 years to reach 95 per cent asymptotic size. The age at growth inflection, which is a proxy for reproductive maturity, occurred at approximately 2-3 years. Comparisons with several small and large predatory theropods reveal that MOR 549 grew faster and matured sooner than they did. These results suggest that Hypacrosaurus was able to partly avoid predators by outgrowing them.     

On integrating climatic change and culture change studies

In the last few decades, advances in understanding and modeling climate have paralleled the growth of an impressive log of radiocarbon dates and quantitative analyses of climatic indicators including pollen, tree rings, and lake levels. At the same time, archeological research has given us an impressive assemblage of cultural information. We also have the tools for sorting out the diverse sources of variance in our datasets. The time has come to begin to integrate these lines of scientific endeavor to produce a mutually coherent picture of at least one of the mechanisms that have affected the history of humankind, and one that undoubtedly will affect the future as well.     

Firing rates of neurons with random excitation and inhibition

The expectation of the interspike interval for a Stein model neuron receiving Poisson excitation and inhibition is determined by solving a differential difference equation with both forward and backward differences. The method of solution relies on an asymptotic expansion at large initial hyperpolarizations. The asymptotic solution is continued to near threshold depolarization whereupon the boundary condition is employed along with recursion relations to obtain the complete solution. The dependency of the mean firing rate on excitation at fixed inhibition and on inhibition at fixed excitation is investigated as well as the threshold dependence at fixed input rates. The results are discussed in relation to those for intracellular current injection and synaptic input to real neurons.     

Firing rates of motoneurons with strong random synaptic excitation

The expected time to firing of a nerve impulse when there is Poisson excitation is calculated exactly in Stein's model. This is done at various input frequencies and various ratios of threshold to epsp magnitude, extending some previous calculations. The appropriate conditions for the validity of the model are discussed. Details of a particular calculation are given which involves the solution of a differential-difference equation. The results are presented as variation of expected time to firing as a function of input frequency for a given threshold to epsp ratio. The experimental results of Redman et al. for Poisson monosynaptic excitation of cat spinal motoneurons lead to the estimation of the epsp size which was not measured. The magnitude of the epsps predicted is in good agreement with that expected under the given conditions of stimulation. The predicted variation of epsp magnitude with input frequency is in accordance with that obtained in other experiments. When the finite rise time of epsps is taken into account the predicted epsp sizes are in better agreement with their expected amplitudes.     

Random drift and culture change

We show that the frequency distributions of cultural variants, in three different real-world examples--first names, archaeological pottery and applications for technology patents--follow power laws that can be explained by a simple model of random drift. We conclude that cultural and economic choices often reflect a decision process that is value-neutral; this result has far-reaching testable implications for social-science research.     

EEG oscillations reflect task effects for the change detection in vocal emotion

How task focus affects recognition of change in vocal emotion remains in debate. In this study, we investigated the role of task focus for change detection in emotional prosody by measuring changes in event-related electroencephalogram (EEG) power. EEG was recorded for prosodies with and without emotion change while subjects performed emotion change detection task (explicit) and visual probe detection task (implicit). We found that vocal emotion change induced theta event-related synchronization during 100–600 ms regardless of task focus. More importantly, vocal emotion change induced significant beta event-related desynchronization during 400–750 ms under explicit instead of implicit task condition. These findings suggest that the detection of emotional changes is independent of task focus, while the task focus effect in neural processing of vocal emotion change is specific to the integration of emotional deviations.     

RNA-DNA ratios in white muscle tissue biopsies reflect recent growth rates of adult brown trout

Recently developed fluorescence techniques were used to quantify RNA-DNA ratios in white epaxial muscle tissue biopsies taken from live adult brown trout. RNA-DNA ratios from small biopsies (4–24 mg wet weight) were measured concurrently with growth over 5 weeks in two groups of brown trout fed different rations, 5% BW day^{– 1} (reference) and 1% BW week^{– 1}(treatment). Reduced rations had significant effects on RNA-DNA ratios in muscle tissue biopsies. The treatment group had significantly lower mean RNA–DNA ratios than the reference group after the first week. After 5 weeks of treatment the mean RNA–DNA ratios of the treatment and reference groups were 1–98 and 4–31, respectively. RNA-DNA ratios from muscle tissue biopsies reflected recent growth rates in the two groups of fish. This technique allows a biochemical measurement of growth rates in adult fish without mortality.     

Temporal patterns in rates of community change during succession

While ecological dogma holds that rates of community change decrease over the course of succession, this idea has yet to be tested systematically across a wide variety of successional sequences. Here, I review and define several measures of community change rates for species presence-absence data and test for temporal patterns therein using data acquired from 16 studies comprising 62 successional sequences. Community types include plant secondary and primary succession as well as succession of arthropods on defaunated mangrove islands and carcasses. Rates of species gain generally decline through time, whereas rates of species loss display no systematic temporal trends. As a result, percent community turnover generally declines while species richness increases--both in a decelerating manner. Although communities with relatively minor abiotic and dispersal limitations (e.g., plant secondary successional communities) exhibit rapidly declining rates of change, limitations arising from harsh abiotic conditions or spatial isolation of the community appear to substantially alter temporal patterns in rates of successional change.     

The politics of culture or a contest of histories: Representations of Chinese popular religion

Conclusion What then are we, a Chinese and a Western anthropologist, doing? As anthropologists we are commenting on the representative character, rather than the truth of all these accounts, the close and the remote. But by bringing them together, we are in addition forcing each others' issues upon them. To unreflective policy and scientific accounts, we bring critical anthropological inquiry. To the uncommitted anthropology of the distant object we ask questions about its political and historical implications.The political equivalent of the anthropologists' straining after a cultural holism is the claim to national unity. National unity and sovereignty in China, as everywhere on the globe since the birth of nationalism in Europe, are asserted with passion. The Chinese nation's cultural soul and moral principle are in acknowledged crisis. The nation is the object of a politics of culture, which requires a research of the singular, if conflictual, history of its necessary emergence. Such a history is a teleology of the nation in the eternal existence of its tradition, already there in culture but not yet entirely apparent or alive to its population. Thus in the PRC, academics, cultural officials, ideological workers, and propagandists insist on national integration and engage in the search for its spiritual civilization. Sometimes, as at present for diplomatic and economic reasons, some provincial autonomy and its restoring of a local cultural identity is encouraged. Cultural workers still, like most Western anthropologists of China, seek answers to the question: what is Chinese-ness? In the PRC the question includes an additional word: what is modern Chinese-ness? The search for the prehistory of modern Chinese-ness for these workers therefore bears a selective project in addition to the teleology of national emergence. Their search is determined by what is meant by modern and therefore what is backward and represents the burden of the past, which has then to be distinguished from what is progressive and represents the future in the past. Western anthropologists are more eclectic, and perhaps less aware, certainly less conscious of their selectivity as an historical act. In China, modern bears the weight of dispute over what stage China has reached in variously conceived histories of human development toward socialism. Modern is not a consistent or a clear set of criteria. It is a contested terrain. The emphasis on socialist modernization can conflict with emphasis on modernization of productivity, technical renewal, and keeping pace with universal scientific knowledge and education. Here is a contest of priorities between ideological and political transformation on the one hand, material incentives, school education, specialization, and economic reform grounded in political and ideological stability on the other. In either case, popular religious practices are superstitious, representing a past that should be left behind.But emphasis upon the necessity for ideological work means a more active attempt to eliminate superstition and in its place construct ideological institutions satisfying the spiritual needs of a new civilization, socialist with Chinese characteristics. This is itself given varied interpretations in action, for even if basic principles can be stated, they are contestable in practice since socialism itself is always in dispute, as is its accommodation to Chinese history and conditions. But such contests always receive the arbitration of one authority, and they become its internal struggles. According to the four basic principles which define patriotism as the party's monopoly of political organization, only the Party can say what the current interpretation of socialism with Chinese characteristics is. It mediates, not Heaven and Earth, but a history of the future and the Chinese people.The second emphasis, on schooling and universal science as instruments of increased production and efficiency, whether that of market forces or of planned growth and improvements of livelihood and social security, merely ignores popular religious practices as relics.A third emphasis focuses upon transformation, rather than neglect or elimination and replacement, stressing the importance of cultural modernization and at the same time the importance of preserving cultural treasures and records.The three emphases in this politics of culture distinguish three strands of state agency: the Party as a Communist organization; the Party and the State Commissions and Ministries—including those of education—as a government of urgent economic and livelihood tasks; and the Ministry of Culture. The Party as communists may hold sway over the others, or the Party and its administration as government of an economy may hold sway over its revolutionary communism. The Ministry of Culture never holds sway. It holds a line, in its task of preserving (establishing) national heritage. Between the two poles of its own emphasis, on cultural modernization and on preservation, its workers register the disputes and changing balances of emphasis coming from the other agencies.Public security organs also hold a line, that of securing national sovereignty and unity. As guardians of Party authority they are the most severe agents of the first emphasis, the emphasis upon elimination. They are charged with the task of eliminating challenges to that authority, ideologically suspended in the current mixture of versions of socialist modernity. In performing this job, practices—such as a spirit-medium heralding a new order, or a spirit-writing sect organizing secretly—which represent counterrevolution, according to the current balance of authority, are the target. But more basically, they are charged with the preservation of national sovereignty and its unity. Here the target is the celebration of any religious and cultural autonomy, which is interpreted as splittist or as unpatriotic.For all these emphases on modernity, popular religious practices in the countryside are local and remote. The alternative emphases of their representations are superstition or survival, ignorance and backwardness, or disappearing history. Academic and museum researchers, social scientists and folklorists have passed through channels of schooling and higher education whose teachers and curricula have been among the chief generators of these very emphases on modernization and national construction. Rural and local religious practices are studied in social science as pathological symptoms of spiritual or economic deprivation, in folklore culturology as historical relics or as local elements of a national heritage.But their research as an activity and its results as data are also resorts and resources for an inversion of the distance at which the local and the remote is held. Writers, artists, and film-makers who have passed through the same passages to modern urban life, have used research into popular rural culture rebelliously.⁵⁰ Chinese modernizing nationalists participate no less than nationalists of other countries in the romanticism which is the inverse of socialist or liberal modernization and rationality. The search for tradition is not confined to current policies of scientific progress, cultural transformation, or of governmental establishment of a national ethos.The perspective of distance from urban heights upon the local and the remote can be turned rebelliously upon a populist leadership or into a hankering for the sources of a blocked and polluted creativity. The peasant roots of the communist revolution have been invoked to comdemn old veterans and feudal workstyles. They have on the other hand been remembered as a lost but revivable sense of community and responsiblity before it was corrupted. Or they are remembered ambivalently as a continuing, betrayed, yellow earth of despair.⁵¹ The Western anthropology of Chinese rural religion and ritual is removed from the Chinese polity but participates in the same distancing perspective. Foreign social science which respects the local and the remote can be condemned as out of order, politically hostile, or shallow—not understanding Chinese culture. On the other hand, these qualities can be put in positive terms—knowledge for its own sake, acquired independently, revealing truths hidden from the partial and the Party-bound.When translated back into Chinese, such foreign research is doubly exotic. It comes from the widest reaches of aspiration to human science, but deals in local detail and cultural holism. It can serve the purposes of the emphasis on folklorist preservation and the emphasis on the national heritage of local elements. On the other hand, it can serve the purposes of romantic rebellion. Its exoticism favors the second. In either case, it simply extends the adoption of humanist categories in the construction of national polities. But as internationally authenticated academic science, it is clearly a challenge to the modernizing social policy science of Chinese academics and policy makers. It discloses and respects the contemporary social life of what they condemn, with increasing enforcement, as backward relics, as pathological symptoms, as anti-patriotic local culture, or secret organizations.Where does that leave us, who have brought these strands together in a single overview? Not in the comfort of celebrating a postmodern mish-mash of representations. For there are definite clashes involved in these differences of emphasis and representation, and unequal forces are involved. We do insist on resisting the temptation to see in any one of them the truth, the correct representation. We see them as histories, or rather as history-making tendencies. But we are left in the uneasy position of requiring recognition of conflicting histories and the necessity of negotiation between them.Stephan Feuchtwang and Wang Ming-ming are, respectively, Principal Researcher and Research Scholar in the China Research Unit of the Department of Social Sciences, University of London