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Epidemic dynamics in census-calibrated modular contact network. NETWORK MODELING AND ANALYSIS IN HEALTH INFORMATICS AND BIOINFORMATICS 2023; 12:14. [PMID: 36685658 PMCID: PMC9838429 DOI: 10.1007/s13721-022-00402-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 11/30/2022] [Accepted: 12/06/2022] [Indexed: 01/11/2023]
Abstract
Network-based models are apt for understanding epidemic dynamics due to their inherent ability to model the heterogeneity of interactions in the contemporary world of intense human connectivity. We propose a framework to create a wire-frame that mimics the social contact network of the population in a geography by lacing it with demographic information. The framework results in a modular network with small-world topology that accommodates density variations and emulates human interactions in family, social, and work spaces. When loaded with suitable economic, social, and urban data shaping patterns of human connectance, the network emerges as a potent decision-making instrument for urban planners, demographers, and social scientists. We employ synthetic networks to experiment in a controlled environment and study the impact of zoning, density variations, and population mobility on the epidemic variables using a variant of the SEIR model. Our results reveal that these demographic factors have a characteristic influence on social contact patterns, manifesting as distinct epidemic dynamics. Subsequently, we present a real-world COVID-19 case study for three Indian states by creating corresponding surrogate social contact networks using available census data. The case study validates that the demography-laced modular contact network reduces errors in the estimates of epidemic variables.
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Pfau D, Jordan CL, Breedlove SM. The De-Scent of Sexuality: Did Loss of a Pheromone Signaling Protein Permit the Evolution of Same-Sex Sexual Behavior in Primates? ARCHIVES OF SEXUAL BEHAVIOR 2021; 50:2267-2276. [PMID: 31016493 DOI: 10.1007/s10508-018-1377-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 12/12/2018] [Accepted: 12/13/2018] [Indexed: 05/15/2023]
Abstract
Primate same-sex sexual behavior (SSSB) is rarely observed in strepsirrhine species, and only somewhat more common in platyrrhines, but is observed in nearly all catarrhine species, including humans, suggesting the common catarrhine ancestor as the origin of routine SSSB. In mice, disruption of the transient receptor potential cation channel 2 (TRPC2) gene, which is crucial for transducing chemosensory signals from pheromones in the vomeronasal organ, greatly increased the likelihood of SSSB. We note that catarrhine primates share a common deleterious mutation in this gene, indicating that the protein was dysfunctional in the common catarrhine ancestral primate approximately 25 mya (million years ago). We hypothesize that the loss of this protein for processing pheromonal signals in males and females made SSSB more likely in a primate ancestral species by effectively lifting a pheromonally mediated barrier to SSSB and that this was an important precursor to the evolution of such behavior in humans. Additional comparisons between SSSB and the functional status of the TRPC2 gene or related proteins across primate species could lend support to or falsify this hypothesis. Our current research indicates that loss of TRPC2 function in developing mice leads to the loss or attenuation of sexually dimorphisms in the adult brain, which may help us to understand the biological underpinnings of SSSB. Our hypothesis offers an ultimate evolutionary explanation for SSSB in humans.
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Affiliation(s)
- Daniel Pfau
- Neuroscience Program, Michigan State University, Giltner Hall, 293 Farm Lane, Room 108, East Lansing, MI, 48824-1101, USA.
| | - Cynthia L Jordan
- Neuroscience Program, Michigan State University, Giltner Hall, 293 Farm Lane, Room 108, East Lansing, MI, 48824-1101, USA
| | - S Marc Breedlove
- Neuroscience Program, Michigan State University, Giltner Hall, 293 Farm Lane, Room 108, East Lansing, MI, 48824-1101, USA
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Lindenfors P, Wartel A, Lind J. 'Dunbar's number' deconstructed. Biol Lett 2021; 17:20210158. [PMID: 33947220 PMCID: PMC8103230 DOI: 10.1098/rsbl.2021.0158] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 04/14/2021] [Indexed: 12/14/2022] Open
Abstract
A widespread and popular belief posits that humans possess a cognitive capacity that is limited to keeping track of and maintaining stable relationships with approximately 150 people. This influential number, 'Dunbar's number', originates from an extrapolation of a regression line describing the relationship between relative neocortex size and group size in primates. Here, we test if there is statistical support for this idea. Our analyses on complementary datasets using different methods yield wildly different numbers. Bayesian and generalized least-squares phylogenetic methods generate approximations of average group sizes between 69-109 and 16-42, respectively. However, enormous 95% confidence intervals (4-520 and 2-336, respectively) imply that specifying any one number is futile. A cognitive limit on human group size cannot be derived in this manner.
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Affiliation(s)
- Patrik Lindenfors
- Institute for Futures Studies, Box 591, 101 31 Stockholm, Sweden
- Centre for Cultural Evolution, Stockholm University, Sweden
| | - Andreas Wartel
- Centre for Cultural Evolution, Stockholm University, Sweden
| | - Johan Lind
- Centre for Cultural Evolution, Stockholm University, Sweden
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Cook JR, Platek SM, Espinoza CN. Proposed symptom-based model of the origins of schizophrenia. Med Hypotheses 2019; 134:109428. [PMID: 31678901 DOI: 10.1016/j.mehy.2019.109428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 10/03/2019] [Accepted: 10/10/2019] [Indexed: 10/25/2022]
Abstract
Schizophrenia is considered a severe mental illness and effects an estimated 1% of the world population. The evidence suggests that incidence rate has been and will continue to be stable over time. Here we adopt a symptomatology-focused evolutionary informed approach to discuss the possible biological adaptations of various presentations of schizophrenia. It is our contention that rather than thinking about schizophrenia as a single disorder, or even a spectrum of disorders, marked by social maladaptation and personal subjective distress, that an evolutionary interpretation based on adaptive nature of individual, or small clusters of, symptoms could prove to be more useful in better understanding the pathophysiology of schizophrenia and its relationship with other psychiatric diagnoses.
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Young JG, Hébert-Dufresne L, Allard A, Dubé LJ. Growing networks of overlapping communities with internal structure. Phys Rev E 2016; 94:022317. [PMID: 27627327 DOI: 10.1103/physreve.94.022317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 06/06/2023]
Abstract
We introduce an intuitive model that describes both the emergence of community structure and the evolution of the internal structure of communities in growing social networks. The model comprises two complementary mechanisms: One mechanism accounts for the evolution of the internal link structure of a single community, and the second mechanism coordinates the growth of multiple overlapping communities. The first mechanism is based on the assumption that each node establishes links with its neighbors and introduces new nodes to the community at different rates. We demonstrate that this simple mechanism gives rise to an effective maximal degree within communities. This observation is related to the anthropological theory known as Dunbar's number, i.e., the empirical observation of a maximal number of ties which an average individual can sustain within its social groups. The second mechanism is based on a recently proposed generalization of preferential attachment to community structure, appropriately called structural preferential attachment (SPA). The combination of these two mechanisms into a single model (SPA+) allows us to reproduce a number of the global statistics of real networks: The distribution of community sizes, of node memberships, and of degrees. The SPA+ model also predicts (a) three qualitative regimes for the degree distribution within overlapping communities and (b) strong correlations between the number of communities to which a node belongs and its number of connections within each community. We present empirical evidence that support our findings in real complex networks.
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Affiliation(s)
- Jean-Gabriel Young
- Département de Physique, de Génie Physique, et d'Optique, Université Laval, Québec (Québec), Canada G1V 0A6
| | - Laurent Hébert-Dufresne
- Département de Physique, de Génie Physique, et d'Optique, Université Laval, Québec (Québec), Canada G1V 0A6
- Santa Fe Institute, Santa Fe, New Mexico 87501, USA
| | - Antoine Allard
- Département de Physique, de Génie Physique, et d'Optique, Université Laval, Québec (Québec), Canada G1V 0A6
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, Barcelona, Spain
| | - Louis J Dubé
- Département de Physique, de Génie Physique, et d'Optique, Université Laval, Québec (Québec), Canada G1V 0A6
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Modeling group size and scalar stress by logistic regression from an archaeological perspective. PLoS One 2014; 9:e91510. [PMID: 24626241 PMCID: PMC3953443 DOI: 10.1371/journal.pone.0091510] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 02/12/2014] [Indexed: 11/24/2022] Open
Abstract
Johnson’s scalar stress theory, describing the mechanics of (and the remedies to) the increase in in-group conflictuality that parallels the increase in groups’ size, provides scholars with a useful theoretical framework for the understanding of different aspects of the material culture of past communities (i.e., social organization, communal food consumption, ceramic style, architecture and settlement layout). Due to its relevance in archaeology and anthropology, the article aims at proposing a predictive model of critical level of scalar stress on the basis of community size. Drawing upon Johnson’s theory and on Dunbar’s findings on the cognitive constrains to human group size, a model is built by means of Logistic Regression on the basis of the data on colony fissioning among the Hutterites of North America. On the grounds of the theoretical framework sketched in the first part of the article, the absence or presence of colony fissioning is considered expression of not critical vs. critical level of scalar stress for the sake of the model building. The model, which is also tested against a sample of archaeological and ethnographic cases: a) confirms the existence of a significant relationship between critical scalar stress and group size, setting the issue on firmer statistical grounds; b) allows calculating the intercept and slope of the logistic regression model, which can be used in any time to estimate the probability that a community experienced a critical level of scalar stress; c) allows locating a critical scalar stress threshold at community size 127 (95% CI: 122–132), while the maximum probability of critical scale stress is predicted at size 158 (95% CI: 147–170). The model ultimately provides grounds to assess, for the sake of any further archaeological/anthropological interpretation, the probability that a group reached a hot spot of size development critical for its internal cohesion.
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Gowlett J, Gamble C, Dunbar R. Human Evolution and the Archaeology of the Social Brain. CURRENT ANTHROPOLOGY 2012. [DOI: 10.1086/667994] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Antiquity and Social Functions of Multilevel Social Organization Among Human Hunter-Gatherers. INT J PRIMATOL 2012. [DOI: 10.1007/s10764-012-9634-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Dunbar RIM. Social cognition on the Internet: testing constraints on social network size. Philos Trans R Soc Lond B Biol Sci 2012; 367:2192-201. [PMID: 22734062 PMCID: PMC3385686 DOI: 10.1098/rstb.2012.0121] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The social brain hypothesis (an explanation for the evolution of brain size in primates) predicts that humans typically cannot maintain more than 150 relationships at any one time. The constraint is partly cognitive (ultimately determined by some aspect of brain volume) and partly one of time. Friendships (but not necessarily kin relationships) are maintained by investing time in them, and failure to do so results in an inexorable deterioration in the quality of a relationship. The Internet, and in particular the rise of social networking sites (SNSs), raises the possibility that digital media might allow us to circumvent some or all of these constraints. This allows us to test the importance of these constraints in limiting human sociality. Although the recency of SNSs means that there have been relatively few studies, those that are available suggest that, in general, the ability to broadcast to many individuals at once, and the possibilities this provides in terms of continuously updating our understanding of network members' behaviour and thoughts, do not allow larger networks to be maintained. This may be because only relatively weak quality relationships can be maintained without face-to-face interaction.
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Affiliation(s)
- R I M Dunbar
- Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
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