This project investigates the relationship between social interactions among marketparticipants and the emergence of cyclical trends in stock markets. Two models aredeveloped to capture the interaction dynamics among individuals within the market:a basic model and a model with a price mechanism. By conducting numerical examplesand systematic simulations, we examine the behavior of these models. Ourfindings reveal that the basic model does not generate cyclical trends in the stockmarket. However, the model incorporating the price mechanism demonstrates theability to create such trends.

Le succès remarquable -écologique et démographique- de l'espèce humaine est largement attribué à notre capacité pour la culture cumulative, i.e. l'accumulation d'innovations culturelles à travers le temps. L'absence ou du moins la rareté de la culture cumulative chez les autres animaux a conduit à de nombreuses spéculations à propos des facteurs nécessaires à son émergence. La culture cumulative dépend étroitement de processus permettant de générer de l'information, et de mécanismes permettant à cette information d'être fidèlement transmise entre les individus. A l'aide d'une approche expérimentale basée sur l'utilisation de jeux sur ordinateur, nous montrons que la capacité d'imitation des patrons comportementaux peut grandement faciliter la fidélité de transmission des informations culturelles. De même, une grande taille de population contribue à la stabilisation des informations culturelles, particulièrement dans le cas d'informations complexes. Cependant, la culture cumulative requiert également la production d'innovations qui ne peut résulter de ces seuls facteurs. D'un point de vue théorique, les innovations sont généralement plus coûteuses à produire qu'à copier, de sorte que la sélection peut difficilement opérer au profit des innovateurs. Nos résultats nous permettent cependant d'avancer que l'émergence d'objets culturels technologiquement opaques pourrait permettre aux innovateurs de bénéficier plus largement de leurs innovations. L'émergence de l'opacité technologique pourrait ainsi constituer un pivot dans l'évolution de la culture cumulative, permettant de favoriser à la fois l'innovation et les mécanismes fidèles de transmission d'information. Les capacités à hiérarchiser et planifier ses actions étant essentiel à la production d'objets culturels technologiquement opaques, il est possible que l'absence apparente de culture cumulative chez les animaux non-humains soit due à un moindre développement de ces capacités cognitives. Finalement nous proposons que la complexité de la culture humaine repose sur quatre facteurs principaux : capacité à hiérarchiser et planifier ses actions, capacité à imiter, collaboration interindividuelle et grande taille de population. / The remarkable success – both ecological and demographic- of the human species is widely attributed to our capability for cumulative culture, i.e. the accumulation of innovations over time. The lack or at least the rarity of cumulative culture in non-human animals has led to much speculation about factors enabling its emergence. Cumulative culture strongly depends on processes allowing generating information, and mechanisms allowing information to be efficiently transmitted between individuals. Using a computer-based experimental approach, we show that process-copying ability improves the fidelity of cultural information transmission. Also, population size contributes to the stability of cultural information, especially for complex information. However, cumulative culture also requires the creation of new innovations, which cannot be the outcome of these factors. From a theoretical point of view, innovations are generally costlier to produce than to copy, so that selection hardly favours innovators. From our results, we propose that the emergence of technologically opaque cultural traits may allow innovators to more widely benefit from their innovations. Thus, the emergence of technological opacity could be pivotal in the rise of cumulative culture, allowing favouring innovation and faithful copying mechanisms. Because the ability to plan actions in a hierarchical way is pivotal to produce technologically opaque cultural artefacts, the lack of cumulative culture in non-human animals could be due to limitations of these cognitive skills. Finally, we propose that human cultural complexity depends on four main factors: the ability to plan actions in a hierarchical way, the ability to process-copy, inter-individual collaboration and large population size.

Written language provides a snapshot of linguistic, cultural, and current events information for a given time period. Aggregating these snapshots by studying many texts over time reveals trends in the evolution of language, culture, and society. The ever-increasing amount of electronic text, both from the digitization of books and other paper documents to the increasing frequency with which electronic text is used as a means of communication, has given us an unprecedented opportunity to study these trends. In this dissertation, we use hundreds of thousands of books spanning two centuries scanned by Google, and over 100 billion messages, or ‘tweets’, posted to the social media platform, Twitter, over the course of a decade to study the English language, as well as study the evolution of culture and society as inferred from the changes in language. We begin by studying the current state of verb regularization and how this compares between the more formal writing of books and the more colloquial writing of tweets on Twitter. We find that the extent of verb regularization is greater on Twitter, taken as a whole, than in English Fiction books, and also for tweets geotagged in the United States relative to American English books, but the opposite is true for tweets geotagged in the United Kingdom relative to British English books. We also find interesting regional variations in regularization across counties in the United States. However, once differences in population are accounted for, we do not identify strong correlations with socio-demographic variables. Next, we study stretchable words, a fundamental aspect of spoken language that, until the advent of social media, was rarely observed within written language. We examine the frequency distributions of stretchable words and introduce two central parameters that capture their main characteristics of balance and stretch. We explore their dynamics by creating visual tools we call ‘balance plots’ and ‘spelling trees’. We also discuss how the tools and methods we develop could be used to study mistypings and misspellings, and may have further applications both within and beyond language. Finally, we take a closer look at the English Fiction n-gram dataset created by Google. We begin by explaining why using token counts as a proxy of word, or more generally, ‘n-gram’, importance is fundamentally flawed. We then devise a method to rebuild the Google Books corpus so that meaningful linguistic and cultural trends may be reliably discerned. We use book counts as the primary ranking for an n-gram and use subsampling to normalize across time to mitigate the extraneous results created by the underlying exponential increase in data volume over time. We also combine the subsampled data over a number of years as a method of smoothing. We then use these improved methods to study linguistic and cultural evolution across the last two centuries. We examine the dynamics of Zipf distributions for n-grams by measuring the churn of language reflected in the flux of n-grams across rank boundaries. Finally, we examine linguistic change using wordshift plots and a rank divergence measure with a tunable parameter to compare the language of two different time periods. Our results address several methodological shortcomings associated with the raw Google Books data, strengthening the potential for cultural inference by word changes.

To what extent can two 'Modes' be found amongst non-state armed groups (NSAGs)? The Modes theory hypotheses that NSAGs are organized into two distinct Modes, either the 'Imagistic' or the 'Doctrinal' Mode, with each Mode characterised by a particular organisational structure and type of resource extraction. Previous preliminary research on this had three limitations: 1) it used a sample of only five groups; 2) "Galton's problem", i.e. non-independence of groups was not taken into account, and 3) the theory of resource extraction was underdeveloped. The present research overcomes each of these limitations. First, can the patterns found in the 5-group case study be replicated with a larger sample? A dataset with 50 NSAGs was constructed, with variables that were derived from the theory and resembling those used for the 5-group case study. Analysis results showed that a few 'Doctrinal' variables were significantly correlated and 'Doctrinal' rituals had a frequency distribution as predicted. Yet, most correlations between all Modes variables were not significant, and analyses did not convincingly show that there were two distinct Modes. Second, to what extent does "Galton's problem" (autocorrelation) play a role amongst NSAGs regarding their Modes properties? Data on relations between armed groups and their geographical locations were added to the sample. Using Moran's I, it appeared that two to four Modes properties were significantly autocorrelated. With geographical region as covariate, analyses were redone. Results remained basically the same as without regional covariate. Third, what is the relationship between Modes and the type of Resource extraction? Resource types were operationalized and Resource type data were added to the sample of NSAGs. A theory on Risk, and a ROI (Return on Investment) and Risk index were developed. Regressions showed no change in ROI or Risk over time. Low ROI did not typically predict Doctrinal-related Modes properties, and high-ROI did not typically predict Imagistic-related Modes properties. The significance of relations between Modes properties and Resource types strongly depended on whether the analysis was a correlation or a regression. Overall, only a few relationships were significant and no consistent pattern emerged. Limitations of the present research, and suggestions for further research are discussed, as well as an overall assessment of the Modes theory.

Cette dissertation est composée de trois articles traitant de sujets divers. Le premier développe une théorie sur la transmission de normes culturelles. Le second article traite de l'évolution des doctrines religieuses dans une économie productive. Enfin, le dernier article de cette dissertation est un travail joint avec Thierry Verdier. L'article propose une nouvelle approche des élections impliquant un nombre arbitraire de candidats. Cette problématique de recherche est importante non seulement quant à sa complexité théorique, mais aussi parce qu'elle permet d'étudier relativement simplement la structure des marchés politiques.Le premier article présente une théorie sur le développement de l'enfant et les pratiques parentales. Dans le modèle, un parent cherche à transmettre des normes comportementales à son enfant en lui envoyant des signaux, que l'enfant observe de manière imparfaite. L'enfant peut cependant augmenter la qualité des signaux qu'il reçoit en investissant dans l'acquisition de compétences cognitives.Nous établissons que les styles parentaux autoritaires ou permissifs décroissent l'accumulation de compétences cognitives. De plus, puisque les interactions entre parents et enfants visent à transmettre des normes comportementales, l'enfant développe un capital d'appréciation pour le développement de compétences cognitives.Notre perspective culturelle sur la question du développement cognitif fournit une grille d'interprétation utile pour divers résultats établis dans la littérature empirique sur le développement de l'enfant.Le second article propose une théorie de la prohibition religieuse contre l'usure et l'innovation et ses conséquences sur les activités et les occupations économiques.Comme une interdiction économique provenant de la religion majoritaire est soutenue par un risque d'exclusion sociale de ce groupe culturel, elle a moins d'effets sur les minorités religieuses. Cela implique que seules les minorités religieuses choisissent des activités qui vont à l'encontre de la prohibition à l'équilibre.Dans le dernier article, nous présentons une théorie micro-fondée de la concurrence politique à plusieurs candidats prenant une perspective ``d'organisation industrielle" de la politique. Nous présentons d'abord un modèle de vote aléatoire qui utilise des distributions introduites par le mathématicien français Maurice Fréchet et qui portent son nom. Ces distributions permettent d'exprimer les parts de vote des différents candidats comme des ``contest functions'', ce qui permet d'établir un théorème d'existence et d'unicité d'un équilibre des stratégies politiques dans des élections impliquant un nombre arbitraire de candidats.Le cadre analytique s'avère suffisamment souple pour traiter plusieurs applications sur des thèmes liés à la structure endogène des marchés politiques. Nous montrons en particulier que le degré d'information des électeurs sur les plateformes ainsi que les campagnes médiatiques impliquent un degré de fragmentation politique plus faible. / The first chapter of this dissertation presents a theory of child development and parental rearingpractices. In the model, a benevolent parent seeks to transmit cultural norms to her child, whoacquires cognitive skills and develops a capital of appreciation for adopting behaviors that accordwith these norms. Our cultural perspective on the issue of cognitive development provides aninterpretation grid for various results established in the empirical literature. It also permits to identifythe parental characteristics that are conducive to various parenting styles, to child neglect and tochild maltreatment.The second chapter provides a theory of religious prohibition against usury and innovation and itsconsequences on economic activities and occupations. As an economic prohibition from themajority religion is sustained by a threat of social exclusion from that cultural group, it has lesseffects on religious minorities. It then creates an occupational pattern where only the religiousminorities choose activities that transgress the prohibition. By creating resentment against thereligious minorities, this occupational pattern strengthens the diffusion of the majority religion in thepopulation. An economic prohibition is then instigated by the clerics in the majority religion,because it allows them to consolidate their norms and to increase the scope of their control overpopular masses. This work also demonstrates that an economic prohibition lasts longer whenreligious clerics can legitimize secular rulers and when the competition on the religious market isweaker.In the last chapter, we present a microfounded theory of multi-candidate political competition takingan "industrial organization" perspective of politics. The analytical framework is shown to be exibleenough to address several applications on the topics of special interest politics, coalition formationin the legislature in proportional elections, and redistribution under alternative electoral rules

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The aim of this thesis is to investigate how discussions in archaeology and genetics influence the consensus on human origins and migrations in the South Pacific. By analyzing the genetic research on chicken- and sweet potato-DNA, I present a general overview of how genetics and archaeology shape the understanding of how humans have colonized the Pacific. By deconstructing a review on how the Pacific was settled based on aDNA, I analyze a geneticist’s perspective on archaeological problems. Through this analysis I suggest how archaeology should be approached on a theoretical level in order to be relevant in understanding human migrations in the Pacific. I propose that archaeology’s strength lie in interpreting material culture through an agency perspective in order to reach a dimension not obtainable by biological perspectives / Syftet med denna uppsats är att undersöka hur diskussioner i arkeologi och genetik påverkar hur vi ser på mänskliga migrationer i Oceanien. Genom att analysera den genetiska forskning som gjorts på kyckling och sötpotatis ges en övergripande bild av hur genetik och arkeologi formar den förståelse som finns för hur människan koloniserat Söderhavet. Genom att dekonstruera en sammanställning av den genetiska forskning som gjorts på mänskligt DNA i Oceanien analyseras en genetikers synsätt på arkeologiska problemställningar. Genom analysen i denna uppsats föreslår jag hur arkeologi borde arbeta på ett teoretiskt plan för att vara relevant i hur vi förstår Oceaniens migrationsmönster. Jag föreslår att arkeologins styrka ligger i att tolka den materiella kulturen genom ett agency-perspektiv för att komma åt en dimension av migrationsproblematiken som inte går att nås genom biologiska perspektiv.

This study investigated stable-isotope ratio evidence of weaning for the late Anglo-Saxon population of Raunds Furnells, Northamptonshire, UK. delta(15)N and delta(13)C values in rib collagen were obtained for individuals of different ages to assess the weaning age of infants within the population. A peak in delta(15) N values at about 2-year-old, followed by a decline in delta(15) N values until age three, indicates a change in diet at that age. This change in nitrogen isotope ratios corresponds with the mortality profile from the site, as well as with archaeological and documentary evidence on attitudes towards juveniles in the Anglo-Saxon period. The pattern of delta(13) C values was less clear. Comparison of the predicted age of weaning to published data from sites dating from the Iron Age to the 19th century in Britain reveals a pattern of changing weaning practices over time, with increasingly earlier commencement and shorter periods of complementary feeding in more recent periods. Such a change has implications for the interpretation of socioeconomic changes during this period of British history, since earlier weaning is associated with decreased birth spacing, and could thus have contributed to population growth.

Contemporary social science research has often focused on nuclear family relationships, and has largely neglected kinship and family outside the nuclear household. In this doctoral thesis I explore demographic issues from a multigenerational perspective, using Swedish register data and mathematical modeling. In different chapters I examine intergenerational transmission of fertility—the relationship between the number of siblings and other kin, and the fertility of an individual. The thesis demonstrates the possibilities for empirical research on family and kinship based on Swedish register data. Unique linkage opportunities across three and four generations are applied to previously unexplored research questions. The studies in the thesis demonstrate the importance of kin outside the household, such as grandparents, aunts/uncles, and cousins, for fertility and family dynamics. / Samhällsvetenskaplig forskning har i hög grad varit fokuserad på kärnfamiljer, och i lägre grad undersökt släktskap utanför hushållet. Den här avhandlingen undersöker demografiska frågor utifrån ett flergenerationsperspektiv med hjälp av svenska registerdata och matematisk modellering. I de olika studierna undersöker jag den sociala överföringen av barnafödande mellan fler generationer—sambanden mellan antalet syskon och andra familjemedlemmar, och en persons barnafödande. Avhandlingen demonstrerar hur svenska registerdata möjliggör empirisk forskning om familj och släktskap. De unika kopplingsmöjligheterna över tre till fyra generationer appliceras på tidigare outforskade forskningsfrågor. Avhandlingen visar vikten av släktskap utanför kärnfamiljen, så som far/mor-föräldrar samt kusiner, för familjedemografiska processer.

I develop social evolution theory to study the evolution of cooperation as follows: (1) Many organisms undergo a dispersal phase prior to breeding; I demonstrate that knowing ones dispersal status aids the evolution of helping (by non-dispersers) and harming (by dispersers). (2) Policing driven by group-benefits may be selected to enforce cooperation in human and animal societies. I extend existing theory to show that policing may be harder to evolve that previously thought, but that it is maintained more readily than it evolves. (3) Archeological and anthropological evidence suggests that warfare was prevalent during our evolution. I show that, contrary to previous suggestions, between-group competition can favour any social behaviour (pro-social or anti-social) so long as it helps the group compete, and that such traits can be altruistic or mutually beneficial. (4) Reproductive leveling is analogous to policing; in the human literature there is doubt as to whether it can evolve. I extend my previous work to consider the coevolution of culturally and genetically inherited traits for reproductive leveling and selfishness. I find that cooperation can evolve between non-kin if they share the same culture. (5) Monogamy is thought to favour the evolution of cooperative breeding. I show that in the simplest case, because of the cost of competition between non-dispersing siblings, the level of promiscuity has little or no effect on the evolution of cooperation. (6) Spatial structure (limited dispersal) is thought to favour the evolution of inter-specific mutualisms as it aligns the partners’ interests. I consider the case of plant-fungi mutualisms and show that spatial structure can disfavour cooperation if it limits the potential fungal partners available to the plant.