R. Alexander Bentley

Prehistoric human migration in the Linearbandkeramik of Central Europe

This paper presents a revised chronology for the Linearbandkeramik and strontium isotope measurements of human skeletal material from two cemeteries which indicate a high incidence of migration. It appears that LBK farmers were highly migratory and interacted with surrounding communities.

Drift as a mechanism for cultural change: an example from baby names.

In the social sciences, there is currently no consensus on the mechanism by which cultural elements come and go in human society. For elements that are value-neutral, an appropriate null model may be one of random copying between individuals in the population. We show that the frequency distributions of baby names used in the United States in each decade of the twentieth century, for both males and females, obey a power law that is maintained over 100 years even though the population is growing, names are being introduced and lost every decade and large changes in the frequencies of specific names are common. We show that these distributions are satisfactorily explained by a simple process in which individuals randomly copy names from each other, a process that is analogous to the infinite-allele model of population genetics with random genetic drift. By its simplicity, this model provides a powerful null hypothesis for cultural change. It further explains why a few elements inevitably become highly popular, even if they have no intrinsic superiority over alternatives. Random copying could potentially explain power law distributions in other cultural realms, including the links on the World Wide Web.

Cultural transmission and stochastic network growth

Archaeological theory has traditionally presupposed the existence of “battleship curves” in stylistic evolution, with little understanding about what governs the width (variant frequency) or length (variant lifespan) of these curves. In terms of these variables, we propose that there is a testable difference between independent decisions, unbiased transmission, and biased transmission in cultural evolution. We expect independent decision making to be represented by an exponential distribution of variant prevalence in the population. In contrast, unbiased transmission tends to be characterized by a power law or log-normal distribution of prevalence, while biased transmission should deviate significantly from the unbiased case. The difference between these categories may be fundamental to how cultural traits spread and persist. In order to make analytical predictions for unbiased transmission, we adapt a model of stochastic network growth that, by quantitatively demonstrating the inherent nonlinearity in unbiased transmission, can explain why a few highly popular styles can be expected to emerge in the course of cultural evolution. For the most part, this model predicts the frequencies of pottery decorations remarkably well over a 400-year span of Linearbandkeramik settlement in the Merzbach valley. Because the highest frequencies of actual motifs are somewhat less than predicted by our unbiased transmission model, we identify an anti-conformist, or pro-novelty, bias in the later phases of the Neolithic Merzbach Valley.

Lapita migrants in The Pacific's oldest cemetery: isotopic analysis at Teouma, Vanuatu

Teouma, an archaeological site on Efate Island, Vanuatu, features the earliest cemetery yet discovered of the colonizers of Remote Oceania, from the late second millennium B.C. In order to investigate potential migration of seventeen human individuals, we measured isotopes of strontium (87Sr/86Sr), oxygen (δ18O), and carbon (δ13C), as well as barium (Ba) and strontium (Sr) concentrations, in tooth enamel from skeletons excavated in the first two field seasons. The majority of individuals cluster with similar isotope and Ba/Sr ratios, consistent with a diet of marine resources supplemented with plants grown on the local basaltic soils. Four outliers, with distinctive 87Sr/86Sr and δ18O, are probably immigrants, three of which were buried in a distinctive position (supine, with the head to the south) with higher Ba/Sr and δ13C, consistent with a terrestrial, nonlocal diet. Among the probable immigrants was a male buried with the crania of three of the locally raised individuals on his chest.

The Expression of Emotions in 20th Century Books

We report here trends in the usage of “mood” words, that is, words carrying emotional content, in 20th century English language books, using the data set provided by Google that includes word frequencies in roughly 4% of all books published up to the year 2008. We find evidence for distinct historical periods of positive and negative moods, underlain by a general decrease in the use of emotion-related words through time. Finally, we show that, in books, American English has become decidedly more “emotional” than British English in the last half-century, as a part of a more general increase of the stylistic divergence between the two variants of English language.

The Neolithic transition in Europe: comparing broad scale genetic and local scale isotopic evidence

Genetic studies of modern populations are raising many interesting questions about how far the modern gene pool is owed to incoming populations during the agricultural revolution in Neolithic Europe. But, as the authors show, studies of isotopic data from cemeteries reveal a picture of increasing subtlety at local level. While early farmers may have been initially newcomers in the upper Rhine they may also have soon intermarried with contemporary hunter-gatherers in the uplands.

Shifting gender relations at Khok Phanom Di, Thailand : isotopic evidence from the skeletons.

The values for isotopes of strontium, carbon, and oxygen in human tooth enamel from the prehistoric site of Khok Phanom Di (ca. 2100–1500 BC) in Thailand shed light on human mobility and marital residence during a crucial period of subsistence change. Khok Phanom Di was a sedentary coastal community that apparently relied on hunting, gathering, and fishing in the midst of a transition to rice agriculture in the interior. The results of the isotope analyses indicate female immigration and then a marked shift to local strontium isotope signatures among females accompanied by a clear increase in the prestige of female burials. A possible explanation is a shift in the pattern of exogamy with a concomitant change in gender relations. Observation of a very similar transition at Ban Chiang, in northeastern Thailand, suggests the possibility of a regionwide social transition. In the case of Khok Phanom Di, the increasing role of females in producing high‐quality ceramic vessels may have contributed to the change.

Evolving social influence in large populations

Darwinian studies of collective human behaviour, which deal fluently with change and are grounded in the details of social influence among individuals, have much to offer “social” models from the physical sciences which have elegant statistical regularities. Although Darwinian evolution is often associated with selection and adaptation, “neutral” models of drift are equally relevant. Building on established neutral models, we present a general, yet highly parsimonious, stochastic model, which generates an entire family of real-world, right-skew socio-economic distributions, including exponential, winner-take-all, power law tails of varying exponents, and power laws across the whole data. The widely used Barabási and Albert (1999) Science 286: 509-512 “B-A” model of preferential attachment is a special case of this general model. In addition, the model produces the continuous turnover observed empirically within these distributions. Previous preferential attachment models have generated specific distributions with turnover using arbitrary add-on rules, but turnover is an inherent feature of our model. The model also replicates an intriguing new relationship, observed across a range of empirical studies, between the power law exponent and the proportion of data represented in the distribution.

Isotopic signatures and hereditary traits: snapshot of a Neolithic community in Germany

A group of Linearbandkeramik people at Talheim, Germany were previously found to have died at the same time, probably in a massacre, and the authors were able to ask some searching questions of their skeletons. The isotope signatures of strontium, oxygen and carbon, which gave information on diet and childhood region, showed up three groups which correlated with hereditary traits (derived previously from the analysis of the teeth). In the local group, there were many local children but no adult women, suggesting they had been selectively taken alive at the time of the massacre. Another group, with isotope signatures derived from upland areas, includes two men who may have been closely related. A third group has a composition suggestive of a nuclear family. The variations of one type of isotope signature with another suggested subtle interpretations, such as transhumance, and a probable labour division in the community between stockholders and cultivators. Here we see the ever-growing potential of these new methods for writing the ‘biographies’ of prehistoric skeletons.

Independent cultural evolution of two song traditions in the chestnut-sided warbler.

In oscine songbirds, song phenotypes arise via gene‐culture coevolution, in which genetically transmitted learning predispositions and culturally transmitted song forms influence one anothers evolution. To assess the outcome of this process in a population of chestnut‐sided warblers (Dendroica pensylvanica), we recorded songs at intervals over a 19‐year period. These recordings revealed the pattern of cultural evolution of songs in our study area, from which we inferred likely learning predispositions and mechanisms of cultural transmission. We found that the species’ two song categories form two distinct cultural traditions, each with its own pattern of change over time. Unaccented‐ending songs have undergone continual, rapid turnover of song and element types, consistent with a model of neutral cultural evolution. Accented‐ending songs, in contrast, persisted virtually unchanged for the entire study period, with extraordinarily constant song form and only one appearance of a new song type. Our results indicate that in songbirds, multiple independent cultural traditions and probably multiple independent learning predispositions can evolve concurrently, especially when different signal classes have become specialized for different communicative functions.