Stockholms universitet

Patrik LindenforsDocent, Forskare

Om mig

Jag har författat några böcker.

Curriculum Vitae

  • Du kan ladda ner min CV här: CV.

Forskning

Kulturell evolution

För närvarande är mitt huvudsakliga forskningsintresse att försöka förstå kulturella förändringar och samhällsförändringar som evolutionära processer. Den här forskningen bedriver jag på Institutet för Framtidsstudier och Centrum för evolutionär kulturforskning. Inom det ämnet har jag två huvudfokus:

  1. Evolutionen av demokrati. Jag är en av flera projektledare inom projektet Varieties of Democracy (V-Dem) som drivs vid Statsvetenskapliga institutionen vid Göteborgs universitet. (Populärvetenskaplig sammanfattning av aktuell artikel).
  2. Evolutionen av religion. Inom det här projektet delar jag upp det man normalt menar med "religion" i sina beståndsdelar och försöker förstå hur dessa delar har uppkommit genom att använda biologiskt och kulturellt evolutionära resonemang.

Däggdjurshjärnans evolution

I det här projektet undersöker jag om art- och könsskillnader i däggdjurs hjärnor kan knytas till könsskillnader i beteenden. Resultaten så här långt visar att beteendeskillnader mellan könen har haft viss inverkan på evolutionen av primaters hjärnor. Projektet har varit vilande ett tag i väntan på nya data som snart ska publiceras.

Sexuell dimorfism

Min övriga forskning har mest fokuserat på användningen av fylogenetiska metoder, speciellt genom analyser av evolutionen av biologiska könsskillnader. Här finns några av mina mest citerade artiklar, om evolutionen av könsskillnader hos däggdjur, hos säldjur, och hos primater, samt om evolutionen av könsskillnader i immunsystemet.

Parasitdiversitet

Under min post-doc vid University of Virginia undersökte jag vilka faktorer som påverkar parasitdiversitet. Informationen om däggdjursparasiter finns publicerad hos Global Mammal Parasite Database. Här återfinns andra av mina mest publicerade artiklar, om parasitrikedom hos rovdjur, samt om parasitdiversitet hos utrotningshotade primater.

Examensarbetare välkomna!

Är du intresserad av att göra examensarbete är du mycket välkommen att maila mig om förslag. Jag har flera idéer som behöver undersökas.

Publikationer

I urval från Stockholms universitets publikationsdatabas

  • Whatever you want

    2019. Andreas Wartel, Patrik Lindenfors, Johan Lind. PLoS ONE 14 (7)

    Artikel

    Primate brains differ in size and architecture. Hypotheses to explain this variation are numerous and many tests have been carried out. However, after body size has been accounted for there is little left to explain. The proposed explanatory variables for the residual variation are many and covary, both with each other and with body size. Further, the data sets used in analyses have been small, especially in light of the many proposed predictors. Here we report the complete list of models that results from exhaustively combining six commonly used predictors of brain and neocortex size. This provides an overview of how the output from standard statistical analyses changes when the inclusion of different predictors is altered. By using both the most commonly tested brain data set and the inclusion of new data we show that the choice of included variables fundamentally changes the conclusions as to what drives primate brain evolution. Our analyses thus reveal why studies have had troubles replicating earlier results and instead have come to such different conclusions. Although our results are somewhat disheartening, they highlight the importance of scientific rigor when trying to answer difficult questions. It is our position that there is currently no empirical justification to highlight any particular hypotheses, of those adaptive hypotheses we have examined here, as the main determinant of primate brain evolution.

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  • An Open Resource for Non-human Primate Imaging

    2018. Michael P. Milham (et al.). Neuron 100 (1), 61-74

    Artikel

    Non-human primate neuroimaging is a rapidly growing area of research that promises to transform and scale translational and cross-species comparative neuroscience. Unfortunately, the technological and methodological advances of the past two decades have outpaced the accrual of data, which is particularly challenging given the relatively few centers that have the necessary facilities and capabilities. The PRIMatE Data Exchange (PRIME-DE) addresses this challenge by aggregating independently acquired non-human primate magnetic resonance imaging (MRI) datasets and openly sharing them via the International Neuroimaging Data-sharing Initiative (INDI). Here, we present the rationale, design, and procedures for the PRIME-DE consortium, as well as the initial release, consisting of 25 independent data collections aggregated across 22 sites (total = 217 non-human primates). We also outline the unique pitfalls and challenges that should be considered in the analysis of non-human primate MRI datasets, including providing automated quality assessment of the contributed datasets.

    Läs mer om An Open Resource for Non-human Primate Imaging
  • Primate Social Evolution

    2018. Patrik Lindenfors. The International Encyclopedia of Anthropology

    Kapitel

    Primates display a remarkable diversity of types of social organization—a diversity that, according to the socioecological model of social evolution, is ultimately determined by ecological factors limiting female fitness and the number of matings limiting male fitness. The foremost ecological determinants of female sociality are the degree to which food resources are defendable, either alone or in a group, and the level of protection from predators gained from being part of a group. Further factors that have been proposed are the presence of infanticide, coalitions, and dominance hierarchies; general population density and habitat saturation; whether competition is mainly intra‐ or intergroup; and which sex disperses. Male sociality is instead mainly determined by the spatiotemporal spacing of mating opportunities with females. Some researchers have also proposed that cognitive abilities impose a limit on group size, since primate sociality demands competent navigation of social networks.

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  • Primate Brain Anatomy

    2018. Ana F. Navarrete (et al.). Brain, behavior, and evolution 91 (2), 109-117

    Artikel

    Since the publication of the primate brain volumetric dataset of Stephan and colleagues in the early 1980s, no major new comparative datasets covering multiple brain regions and a large number of primate species have become available. However, technological and other advances in the last two decades, particularly magnetic resonance imaging (MRI) and the creation of institutions devoted to the collection and preservation of rare brain specimens, provide opportunities to rectify this situation. Here, we present a new dataset including brain region volumetric measurements of 39 species, including 20 species not previously available in the literature, with measurements of 16 brain areas. These volumes were extracted from MRI of 46 brains of 38 species from the Netherlands Institute of Neuroscience Primate Brain Bank, scanned at high resolution with a 9.4-T scanner, plus a further 7 donated MRI of 4 primate species. Partial measurements were made on an additional 8 brains of 5 species. We make the dataset and MRI scans available online in the hope that they will be of value to researchers conducting comparative studies of primate evolution.

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  • Divine Placebo

    2019. Patrik Lindenfors. Human Ecology 47 (2), 157-163

    Artikel

    In this paper, I draw on knowledge from several disciplines to explicate the potential evolutionary significance of health effects of religiosity. I present three main observations. First, traditional methods of religious healers seldom rely on active remedies, but instead focus on lifestyle changes or spiritual healing practices that best can be described as placebo methods. Second, actual health effects of religiosity are thus mainly traceable to effects from a regulated lifestyle, social support networks, or placebo effects. Third, there are clear parallels between religious healing practices and currently identified methods that induce placebo effects. Physiological mechanisms identified to lie behind placebo effects activate the body's own coping strategies and healing responses. In combination, lifestyle, social support networks, and placebo effects thus produce both actual and perceived health effects of religiosity. This may have played an important role in the evolution and diffusion of religion through two main pathways. First, any real positive health effects of religiosity would have provided a direct biological advantage. Second, any perceived health effects, both positive and negative, would further have provided a unique selling point for religiosity' per se. Actual and perceived health effects of religiosity may therefore have played an underestimated role during the evolution of religiosity through both biological and cultural pathways.

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  • On revolutions

    2020. Armand M. Leroi (et al.). Palgrave Communications 6

    Artikel

    Sometimes the normal course of events is disrupted by a particularly swift and profound change. Historians have often referred to such changes as revolutions, and, though they have identified many of them, they have rarely supported their claims with statistical evidence. Here, we present a method to identify revolutions based on a measure of multivariate rate of change called Foote novelty. We define revolutions as those periods of time when the value of this measure is, by a non-parametric test, shown to significantly exceed the background rate. Our method also identifies conservative periods when the rate of change is unusually low. We apply it to several quantitative data sets that capture long-term political, social and cultural changes and, in some of them, identify revolutions - both well known and not. Our method is general and can be applied to any phenomenon captured by multivariate time series data of sufficient quality.

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  • Sequential Requisites Analysis

    2019. Patrik Lindenfors, Joshua Krusell, Staffan I. Lindberg. Social Science Quarterly 100 (3), 838-856

    Artikel

    Objectives: This article presents a new method inspired by evolutionary biology for analyzing longer sequences of requisites for the emergence of particular outcome variables across numerous combinations of ordinal variables in social science analysis.

    Methods: The approach is a sorting algorithm through repeated pairwise investigations of states in a set of variables and identifying what states in the variables occur before states in all other variables. We illustrate the proposed method by analyzing a set of variables from version 7.1 of the V-Dem data set (Coppedge etal. 2017. Varieties of Democracy (V-Dem) Project; Pemstein etal. 2017. University of Gothenburg, Varieties of Democracy Institute: Working Paper No. 21). With a large set of indicators measured over many years, the method makes it possible to identify and compare long, complex sequences across many variables.

    Results: This affords an opportunity, for example, to disentangle the sequential requisites of failing and successful sequences in democratization, or if requisites are different during different time periods.

    Conclusions: For policy purposes, this is instrumental: Which components of democracy occur earlier and which later? Which components of democracy are therefore the ideal targets for democracy promotion at different stages?

    Läs mer om Sequential Requisites Analysis
  • Investigating Sequences in Ordinal Data

    2018. Patrik Lindenfors (et al.). Political Science Research and Methods 6 (3), 449-466

    Artikel

    This paper presents a new approach for studying temporal sequences across ordinal variables. It involves three complementary approaches (frequency tables, transitional graphs, and dependency tables), as well as an established adaptation based on Bayesian dynamical systems, inferring a general system of change. The frequency tables count pairs of values in two variables and transitional graphs depict changes, showing which variable tends to attain high values first. The dependency tables investigate which values of one variable are prerequisites for values in another, as a more direct test of causal hypotheses. We illustrate the proposed approaches by analyzing the V-Dem dataset, and show that changes in electoral democracy are preceded by changes in freedom of expression and access to alternative information.

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  • Women's rights in democratic transitions: A global sequence analysis, 1900–2012

    2017. Yi-ting Wang (et al.). European Journal of Political Research 56 (4), 735-756

    Artikel

    What determines countries’ successful transition to democracy? This article explores the impact of granting civil rights in authoritarian regimes and especially the gendered aspect of this process. It argues that both men's and women's liberal rights are essential conditions for democratisation to take place: providing both women and men rights reduces an inequality that affects half of the population, thus increasing the costs of repression and enabling the formation of women's organising – historically important to spark protests in initial phases of democratisation. This argument is tested empirically using data that cover 173 countries over the years 1900–2012 and contain more nuanced measures than commonly used. Through novel sequence analysis methods, the results suggest that in order to gain electoral democracy a country first needs to furnish civil liberties to both women and men.

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  • Religion vs. Health

    2016. Patrik Lindenfors. World Future Guide 2016, 46-55

    Kapitel

    Religion may affect personal health in at least two ways. First, religious prescriptions concerning matters such as diet, waste, sexual relationships and social support networks may have actual health consequences. Second, religious healing practices may induce placebo and nocebo responses. Through such mechanisms, religion can result in both positive and negative health effects, depending on prescriptions and rituals involved. Contingent on magnitude, health effects may constitute an underestimated component in understanding the prevalence and persistence of religions in human societies. Health aspects of religion may have become important in human societies through natural selection of susceptibility to placebo responses from religious healing rituals, or through cultural selection of components of religions that involve functioning health advice or that have piggy-backed on practices invoking placebo responses. What exact significance health effects have for understanding the persistence and ubiquity of religions remains to be thoroughly investigated, however.

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  • Sequential Requisites Analysis

    2016. Patrik Lindenfors, Joshua Krusell, Staffan I. Lindberg.

    Rapport

    This paper presents a new method inspired by evolutionary biology for analyzing longer sequences of requisites for the emergence of particular outcome variables across numerous combinations of ordinal variables in social science analysis. The approach involves repeated pairwise investigations of states in a set of variables and identifying what states in the variables that occur before states in all other variables. We illustrate the proposed method by analyzing a set of variables from version 6 of the V-Dem dataset (Coppedge et al. 2015a, b). With a large set of indicators measured over many years, the method makes it possible to explore long, complex sequences across many variables in quantitative datasets. This affords an opportunity, for example, to disentangle the sequential requisites of failing and successful sequences in democratization. For policy purposes this is instrumental: Which components of democracy are most exogenous and least endogenous and therefore the ideal targets for democracy promotion at different stages?

    Läs mer om Sequential Requisites Analysis
  • A Novel Method to Analyze Social Transmission in Chronologically Sequenced Assemblages, Implemented on Cultural Inheritance of the Art of Cooking

    2015. Sven Isaksson (et al.). PLoS ONE 10 (5)

    Artikel

    Here we present an analytical technique for the measurement and evaluation of changes in chronologically sequenced assemblages. To illustrate the method, we studied the cultural evolution of European cooking as revealed in seven cook books dispersed over the past 800 years. We investigated if changes in the set of commonly used ingredients were mainly gradual or subject to fashion fluctuations. Applying our method to the data from the cook books revealed that overall, there is a clear continuity in cooking over the ages - cooking is knowledge that is passed down through generations, not something (re-) invented by each generation on its own. Looking at three main categories of ingredients separately (spices, animal products and vegetables), however, disclosed that all ingredients do not change according to the same pattern. While choice of animal products was very conservative, changing completely sequentially, changes in the choices of spices, but also of vegetables, were more unbounded. We hypothesize that this may be due a combination of fashion fluctuations and changes in availability due to contact with the Americas during our study time period. The presented method is also usable on other assemblage type data, and can thus be of utility for analyzing sequential archaeological data from the same area or other similarly organized material.

    Läs mer om A Novel Method to Analyze Social Transmission in Chronologically Sequenced Assemblages, Implemented on Cultural Inheritance of the Art of Cooking
  • The Origins and Maintenance of Female Genital Modification across Africa

    2016. Cody T. Ross (et al.). Human Nature 27 (2), 173-200

    Artikel

    We present formal evolutionary models for the origins and persistence of the practice of Female Genital Modification (FGMo). We then test the implications of these models using normative cross-cultural data on FGMo in Africa and Bayesian phylogenetic methods that explicitly model adaptive evolution. Empirical evidence provides some support for the findings of our evolutionary models that the de novo origins of the FGMo practice should be associated with social stratification, and that social stratification should place selective pressures on the adoption of FGMo; these results, however, are tempered by the finding that FGMo has arisen in many cultures that have no social stratification, and that forces operating orthogonally to stratification appear to play a more important role in the cross-cultural distribution of FGMo. To explain these cases, one must consider cultural evolutionary explanations in conjunction with behavioral ecological ones. We conclude with a discussion of the implications of our study for policies designed to end the practice of FGMo.

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  • Dating human cultural capacity using phylogenetic principles

    2013. Johan Lind (et al.). Scientific Reports 3, 1785

    Artikel

    Humans have genetically based unique abilities making complex culture possible; an assemblage of traits which we term cultural capacity. The age of this capacity has for long been subject to controversy. We apply phylogenetic principles to date this capacity, integrating evidence from archaeology, genetics, paleoanthropology, and linguistics. We show that cultural capacity is older than the first split in the modern human lineage, and at least 170,000 years old, based on data on hyoid bone morphology, FOXP2 alleles, agreement between genetic and language trees, fire use, burials, and the early appearance of tools comparable to those of modern hunter-gatherers. We cannot exclude that Neanderthals had cultural capacity some 500,000 years ago. A capacity for complex culture, therefore, must have existed before complex culture itself. It may even originated long before. This seeming paradox is resolved by theoretical models suggesting that cultural evolution is exceedingly slow in its initial stages.

    Läs mer om Dating human cultural capacity using phylogenetic principles
  • The green beards of language

    2013. Patrik Lindenfors. Ecology and Evolution 3 (4), 1104-1112

    Artikel

    Language transfers information on at least three levels; (1) what is said, (2) how it is said (what language is used), and, (3) that it is said (that speaker and listener both possess the ability to use language). The use of language is a form of honest cooperation on two of these levels; not necessarily on what is said, which can be deceitful, but always on how it is said and that it is said. This means that the language encoding and decoding systems had to evolve simultaneously, through mutual fitness benefits. Theoretical problems surrounding the evolution of cooperation disappear if a recognition system is present enabling cooperating individuals to identify each other if they are equipped with green beards. Here, I outline how both the biological and cultural aspects of language are bestowed with such recognition systems. The biological capacities required for language signal their presence through speech and understanding. This signaling cannot be invaded by false green beards because the traits and the signal of their presence are one and the same. However, the real usefulness of language comes from its potential to convey an infinite number of meanings through the dynamic handling of symbols through language itself. But any specific language also signals its presence to others through usage and understanding. Thus, languages themselves cannot be invaded by false green beards because, again, the trait and the signal of its presence are one and the same. These twin green beards, in both the biological and cultural realms, are unique to language.

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  • Det unikt mänskliga

    2012. Patrik Lindenfors, Johan Lind, Magnus Enquist. Människans kunskap och kunskapen om människan, 31-44

    Kapitel
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  • Evolutionary aspects of aggression

    2011. Patrik Lindenfors, Birgitta Tullberg. Aggression, 7-22

    Kapitel

    Aggressive behaviors in animals, for example, threat, attack, and defense, arecommonly related to competition over resources, competition over matingopportunities, or fights for survival. In this chapter, we focus on aggressivecompetition over mating opportunities, since this competition explains muchof the distribution of weaponry and large body size, but also because this type ofcompetition sheds light on the sex skew in the use of violence in mammals,including humans. Darwin (1871) termed this type of natural selection, wheredifferences in reproductive success are caused by competition over mates, sexualselection. Not all species have a pronounced competition over mates, however.Instead, this aspect of sociality is ultimately determined by ecological factors. 

    In species where competition over mates is rampant, this has evolutionary effectson weaponry and body size such that males commonly bear more vicious weaponsand are larger than females. A review of sexual selection in mammals reveals howcommon aggressive competition over mating opportunities is in this group.Nearly half of all mammal species exhibit male-biased sexual size dimorphism,a pattern that is clearly linked to sexual selection. Sexual selection is alsocommon in primates, where it has left clear historical imprints in body massdifferences, in weaponry differences (canines), and also in brain structure differences.However, when comparing humans to our closest living primate relatives,it is clear that the degree of male sexual competition has decreased in thehominid lineage. Nevertheless, our species displays dimorphism, polygyny, andsex-specific use of violence typical of a sexually selected mammal. Understandingthe biological background of aggressive behaviors is fundamental to understandinghuman aggression.

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  • The cultural evolution of democracy

    2011. Patrik Lindenfors, Fredrik Jansson, Mikael Sandberg. PLoS ONE 6 (11), e28270

    Artikel

    Transitions to democracy are most often considered the outcome of historical modernization processes. Socio-economicchanges, such as increases in per capita GNP, education levels, urbanization and communication, have traditionally been found to be correlates or ‘requisites’ of democratic reform. However, transition times and the number of reform steps havenot been studied comprehensively. Here we show that historically, transitions to democracy have mainly occurred throughrapid leaps rather than slow and incremental transition steps, with a median time from autocracy to democracy of 2.4 years,and overnight in the reverse direction. Our results show that autocracy and democracy have acted as peaks in an evolutionary landscape of possible modes of institutional arrangements. Only scarcely have there been slow incremental transitions. We discuss our results in relation to the application of phylogenetic comparative methods in cultural evolutionand point out that the evolving unit in this system is the institutional arrangement, not the individual country which isinstead better regarded as the ‘host’ for the political system.

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  • Sexual dimorphism in primate aerobic capacity

    2010. Patrik Lindenfors, Liam J Revell, Charles L Nunn. Journal of Evolutionary Biology 23 (6), 1183-1194

    Artikel

    Male intrasexual competition should favour increased male physical prowess.This should in turn result in greater aerobic capacity in males than in females(i.e. sexual dimorphism) and a correlation between sexual dimorphism inaerobic capacity and the strength of sexual selection among species. However,physiological scaling laws predict that aerobic capacity should be lower perunit body mass in larger than in smaller animals, potentially reducing orreversing the sex difference and its association with measures of sexualselection. We used measures of haematocrit and red blood cell (RBC) countsfrom 45 species of primates to test four predictions related to sexual selectionand body mass: (i) on average, males should have higher aerobic capacity thanfemales, (ii) aerobic capacity should be higher in adult than juvenile males,(iii) aerobic capacity should increase with increasing sexual selection, but alsothat (iv) measures of aerobic capacity should co-vary negatively with bodymass. For the first two predictions, we used a phylogenetic paired t-testdeveloped for this study. We found support for predictions (i) and (ii). For prediction (iii), however, we found a negative correlation between the degreeof sexual selection and aerobic capacity, which was opposite to our prediction.Prediction (iv) was generally supported. We also investigated whethersubstrate use, basal metabolic rate and agility influenced physiologicalmeasures of oxygen transport, but we found only weak evidence for acorrelation between RBC count and agility.

    Läs mer om Sexual dimorphism in primate aerobic capacity
  • The Number of Cultural Traits Is Correlated with Female Group Size but Not with Male Group Size in Chimpanzee Communities

    2010. Johan Lind, Patrik Lindenfors. PLoS ONE 5 (3), e9241

    Artikel

    What determines the number of cultural traits present in chimpanzee (Pan troglodytes) communities is poorly understood. In humans, theoretical models suggest that the frequency of cultural traits can be predicted by population size. In chimpanzees, however, females seem to have a particularly important role as cultural carriers. Female chimpanzees use tools more frequently than males. They also spend more time with their young, skewing the infants’ potential for social learning towards their mothers. In Gombe, termite fishing has been shown to be transmitted from mother to offspring. Lastly, it is female chimpanzees that transfer between communities and thus have the possibility of bringing in novel cultural traits from other communities. From these observations we predicted that females are more important cultural carriers than males. Here we show that the reported number of cultural traits in chimpanzee communities correlates with the number of females in chimpanzee communities, but not with the number of males. Hence, our results suggest that females are the carriers of chimpanzee culture.

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  • On sexual dimorphism in immune function

    2009. Charles L Nunn (et al.). Philosophical Transactions of the Royal Society of London. Biological Sciences 364 (1513), 61-69

    Artikel

    Sexual dimorphism in immune function is a common pattern in vertebrates and also in a number of invertebrates. Most often, females are more ‘immunocompetent’ than males. The underlying causes are explained by either the role of immunosuppressive substances, such as testosterone, or by fundamental differences in male and female life histories. Here, we investigate some of the main predictions of the immunocompetence handicap hypothesis (ICHH) in a comparative framework using mammals. We focus specifically on the prediction that measures of sexual competition across species explain the observed patterns of variation in sex-specific immunocompetence within species. Our results are not consistent with the ICHH, but we do find that female mammals tend to have higher white blood cell counts (WBC), with some further associations between cell counts and longevity in females. We also document positive covariance between sexual dimorphism in immunity, as measured by a subset of WBC, and dimorphism in the duration of effective breeding. This is consistent with the application of ‘Bateman's principle’ to immunity, with females maximizing fitness by lengthening lifespan through greater investment in immune defences. Moreover, we present a meta-analysis of insect immunity, as the lack of testosterone in insects provides a means to investigate Bateman's principle for immunity independently of the ICHH. Here, we also find a systematic female bias in the expression of one of the two components of insect immune function that we investigated (phenoloxidase). From these analyses, we conclude that the mechanistic explanations of the ICHH lack empirical support. Instead, fitness-related differences between the sexes are potentially sufficient to explain many natural patterns in immunocompetence.

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  • Democratic revolutions as institutional innovation diffusion

    2013. Fredrik Jansson, Patrik Lindenfors, Mikael Sandberg. Technological forecasting & social change 80 (8), 1546-1556

    Artikel

    Recent ‘democratic revolutions’ in Islamic countries call for a re-consideration of transitions to and from democracy. Transitions to democracy have often been considered the outcome of socio-economic modernization and therefore slow and incremental processes. But as a recent study has made clear, in the last century, transitions to democracy have mainly occurred through rapid leaps rather than slow and incremental steps. Here, we therefore apply an innovation and systems perspective and consider transitions to democracy as processes of institutional, and therefore systemic, innovation adoption. We show that transitions to democracy starting before 1900 lasted for an average of 50 years and a median of 56 years, while transitions originating later took an average of 4.6 years and a median of 1.7 years. However, our results indicate that the survival time of democratic regimes is longer in cases where the transition periods have also been longer, suggesting that patience paid in previous democratizations. We identify a critical ‘consolidation-preparing’ transition period of 12 years. Our results also show that in cases where the transitions have not been made directly from autocracy to democracy, there are no main institutional paths towards democracy. Instead, democracy seems reachable from a variety of directions. This is in line with the analogy of diffusion of innovations at the nation systems level, for which assumptions are that potential adopter systems may vary in susceptibility over time. The adoption of the institutions of democracy therefore corresponds to the adoption of a new political communications standard for a nation, in this case the innovation of involving in principle all adult citizens on an equal basis.

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  • Neocortex evolution in primates: the 'social brain' is for females

    2005. Patrik Lindenfors. Biology Letters 1, 407-410

    Artikel

    According to the social intelligence hypothesis, relative neocortex size should be directly related to the degree of social complexity. This hypothesis has found support in a number of comparative studies of group size. The relationship between neocortex and sociality is thought to exist either because relative neocortex size limits group size or because a larger group size selects for a larger neocortex. However, research on primate social evolution has indicated that male and female group sizes evolve in relation to different demands. While females mostly group according to conditions set by the environment, males instead simply go where the females are. Thus, any hypothesis relating to primate social evolution has to analyse its relationship with male and female group sizes separately. Since sex-specific neocortex sizes in primates are unavailable in sufficient quantity, I here instead present results from phylogenetic comparative analyses of unsexed relative neocortex sizes and female and male group sizes. These analyses show that while relative neocortex size is positively correlated with female group size, it is negatively, or not at all correlated with male group size. This indicates that the social intelligence hypothesis only applies to female sociality.

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  • Sexual size dimorphism in mammals

    2007. Patrik Lindenfors, John L. Gittleman, Kate E. Jones. Sex, size and gender roles, 16-26

    Kapitel

    This chapter explores the pattern of sexual size dimorphism in mammals and the processes that underly its evolution. We find that, on average, male mammals are the larger sex (average male/female mass ratio 1.184), with males being at least 10% larger than females in over 45% of species. Most mammalian orders are also have male-biased sexual dimorphism, although some orders do not show any bias or are significantly female-biased (Lagomorpha). Sexual size dimorphism increases with body size across mammals (Rensch’s rule), suggesting that there are parallel selection pressures on both male and female size. We found support for the hypothesis that male-biased dimorphism relates to sexual selection on males through male–male competition for females. We draw this conclusion from a positive correlation between the degree of sexual selection, as indicated by mating systems and the degree of male biased size dimorphism. The degree of sexual selection was also positively correlated with male and female size across mammals. Further, a parallel selection pressure on female mass is identified in that age at weaning is significantly higher in more polygynous species, even when correcting for body mass. We also explore the processes maintaining smaller female size in sexually dimorphic species and confirm that reproductive rate is lower for larger females, indicating that fecundity selection selects for smaller females in mammals. Although the patterns we discuss hold across mammals as a whole, there is considerable variation across orders and many of these relationships are not significant. Further work is still needed to more closely investigate the pattern of sexual dimorphism and processes driving sexual dimorphism in different clades.

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  • Primate brain architecture and selection in relation to sex

    2007. Patrik Lindenfors, Charles L Nunn, Robert A Barton. BMC Biology 5 (20)

    Artikel

    Background: Social and competitive demands often differ between the sexes in mammals. These differing demands should be expected to produce variation in the relative sizes of various brain structures. Sexual selection on males can be predicted to influence brain components handling sensory-motor skills that are important for physical competition or neural pathways involving aggression. Conversely, because female fitness is more closely linked to ecological factors and social interactions that enable better acquisition of resources, social selection on females should select for brain components important for navigating social networks. Sexual and social selection acting on one sex could produce sexual dimorphism in brain structures, which would result in larger species averages for those same brain structures. Alternatively, sex-specific selection pressures could produce correlated effects in the other sex, resulting in larger brain structures for both males and females of a species. Data are presently unavailable for the sex-specific sizes of brain structures for anthropoid primates, but under either scenario, the effects of sexual and social selection should leave a detectable signal in average sizes of brain structures for different species.

    Results: The degree of male intra-sexual selection was positively correlated with several structures involved in autonomic functions and sensory-motor skills, and in pathways relating to aggression and aggression control. The degree of male intra-sexual selection was not correlated with relative neocortex size, which instead was significantly positively correlated with female social group size, but negatively correlated with male group size.

    Conclusion: Sexual selection on males and social selection on females have exerted different effects on primate brain architecture. Species with a higher degree of male intra-sexual selection carry a neural signature of an evolutionary history centered on physical conflicts, but no traces of increased demands on sociocognitive tasks. Conversely, female sociality is indicated to have driven the evolution of socio-cognitive skills. Primate brain architecture is therefore likely to be a product of ecological and species-specific social factors as well as different sex-specific selection pressures. Our results also highlight the need for acquisition and analysis of sex-specific brain components in mammals.

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  • Phylogenetic analyses of primate size evolution

    1998. Patrik Lindenfors, Birgitta Tullberg. Biological Journal of the Linnean Society 64, 413-447

    Artikel

    We have analysed the relationship between primate mating system, size and size dimorphism by utilizing several phylogenetically based methods. An independent contrast analysis of male and female size (log weight) showed that these are tightly correlated and that size dimorphism is not a simple allometric function of size. We found no relationship between mating system and sexual dimorphism in strepsirhines but a strong relationship in haplorhines. By matched-pairs analysis, where sister groups were matched according to whether the mating system predicted higher or lower intrasexual selection for male size, haplorhine species in more polygynous clades (with a predicted higher sexual selection) were significantly more dimorphic, had larger males, and also, but to a lesser degree, larger females. Both independent contrast and matched-pairs analyses are non-directional and correlational. By using a directional test we investigated how a transition in mating system affects size and dimorphism. Here, each observation is the sum of changes in dimorphism or size in a clade that is defined by a common origin of a mating system. Generally, dimorphism, as well as male and female size, increased after an expected increase in sexual selection, and decreased after an expected decrease in sexual selection. The pattern was, however, not significant for all of the alternative character reconstructions. In clades with an expected increase in sexual selection, male size increased more than female size. This pattern was significant for all character reconstructions. The directional investigation indicates that the magnitude of change in haplorhine dimorphism is larger after an increase in sexual selection than after a decrease, and, for some reconstructions, that the magnitude of size increase is larger than the magnitude of size decrease for both sexes. Possible reasons for these patterns are discussed, as well as their implications as being one possible mechanism behind Cope's rule, i.e. general size increase in many phylogenetic lineages

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