Details of the Researcher

PHOTO

Kenji Itao
Section
Frontier Research Institute for Interdisciplinary Sciences
Job title
Assistant Professor
Degree

  • The doctor of philosophy in the field of multidisciplinary sciences (The University of Tokyo)

e-Rad No.
21000697

Education 2

  • The University of Tokyo　Graduate School of Arts and Sciences　Basic Science,Section of Multi-Disciplinary Sciences,

    2019/04 - 2024/03

  • The University of Tokyo　College of Arts and Sciences

    2015/04 - 2019/03

Awards 13

  1. The Young Scientists’ Award in the Commendation for Science and Technology

    2026/04　The Minister of Education, Culture, Sports, Science and Technology　The research on generative principles of human social structure using mathematical models.

  2. Young Scientist Award of the Physical Society of Japan

    2025/03　The Physical Society of Japan　Principles of the Emergence of Diverse Human Social Structures: Toward the Construction of Universal Anthropology

  3. Inoue Research Award for Young Scientists

    2025/02　Inoue Foundation for Science　Principles of the Emergence of Diverse Human Social Structures: Constructing Universal Anthropology

  4. Ikushi Prize

    2024/01　Japan Society for the Promotion of Science (JSPS)　A study of the diverse structures of human societies and the universal mechanism for their evolution, based on the evolutionary theory, statistical physics, and ethnographic data analysis.

  5. President Award

    2021/03　University of Tokyo　Multi-level Evolution of Family and Society

  6. Research Encouragement Award

    2025/08　Society of Evolutionary Studies, Japan　The study on the evolution of human social structure using mathematical modeling

  7. Young Researcher Presentation Award

    2024/12　Human Behavior and Evolution Society Japan　Two Universal pathways in Demographic Transition

  8. The First Higher School memorial prize

    2024/03　The University of Tokyo, Graduate School of Arts and Sciences　Principles of the Emergence of Diverse Human Social Structures: Constructing Universal Anthropology

  9. Student Presentation Award of the Physical Society of Japan

    2022/03　The Physical Society of Japan

  10. 若手会員大会発表賞

    2021/10　日本人類学会　「婚姻交換による親族構造形成のダイナミクス」

  11. Awards for local student presenters

    2021/06　Cultural Evolution Society Conference 2021 Sapporo　"Evolution of kinship structures driven by marriage tie and competition."

  12. 一高記念賞

    2021/03　東京大学総合文化研究科　「多階層進化モデルによる社会構造の生成」

  13. 若手優秀発表賞

    2020/12　日本人間行動進化学会　「農村社会における家族形態の生成と社会構造の進化」

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Papers 10

  1. Two universal pathways in demographic transition Peer-reviewed

    Kenji Itao

    Evolutionary Human Sciences　1-17　2026/06/15

    Publisher: Cambridge University Press (CUP)

    DOI： 10.1017/ehs.2026.10054 　

    eISSN： 2513-843X

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    Abstract Demographic transition, characterised by declines in fertility and mortality, is a global phenomenon associated with modernisation. While typical patterns of fertility decline have been described mainly in Western countries, their applicability to other regions and the underlying mechanisms remain unclear. Using data spanning 1800–2020 from 237 countries and territories, this study identifies two universal pathways in the change in the crude birth rate (births per 1,000 person-years, λ) and period life expectancy at birth (e0). Most countries’ demographic trajectories follow one of these two pathways or shift between them. These pathways define phases governed by different mechanisms. Phase I, conserving λe0, dominated until the mid-20th century and was characterised by high child mortality and steady population growth. By contrast, Phase II, conserving λ exp(e0/17), has prevailed since 1950 and is marked by low child mortality and steady growth in GDP per capita. A theoretical model considering the trade-off between reproduction and education elucidates the transition between these phases. The transition to Phase II is accelerated by declining educational costs, rising social mobility, and cultural transmission linked to modernisation and Westernisation. This study demonstrates quantitative regularities between fertility and longevity during demographic transition and provides a theoretical lens for their underlying mechanisms.

  2. Self-organized institutions in evolutionary dynamical-systems games Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    Proceedings of the National Academy of Sciences　2025/04/15

    DOI： 10.1073/pnas.2500960122 　

  3. Emergence of economic and social disparities through competitive gift-giving Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    PLOS Complex Systems　2024/09/03

    DOI： 10.1371/journal.pcsy.0000001 　

  4. Formation of human kinship structures depending on population size and cultural mutation rate Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    Proceedings of the National Academy of Sciences　2024/08/13

    DOI： 10.1073/pnas.2405653121 　

  5. Transition of social organisations driven by gift relationships Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    Humanities and Social Sciences Communications　10　(1)　2023/04/29

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1057/s41599-023-01688-w 　

    eISSN： 2662-9992

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    Abstract Anthropologists have observed that gifts bring goods to the recipient and honour to the donor in many human societies. The totality of such social relationships constitutes a network. Social networks characterise different types of social organisations including bands of small kin groups, tribal unions of families, and hierarchically organised chiefdoms. However, the factors and mechanisms that cause the transition between these types have hardly been explained. Here, we focus on gifts as the driving force for such changes. We build the model by idealising gift interactions and simulating the consequent social changes due to long-term massive interactions. In the model, people give their wealth to each other, produce wealth, and reciprocate for the gift. Gifts and reciprocation strengthen relationships. Through simulation, we demonstrate that, as the frequency and scale of gifts increase, economic and social disparities successively arise. Simultaneously, network structures shift from bands to tribes and then, chiefdoms. Statistical analysis using the Standard Cross-Cultural Sample, a global ethnographic database, empirically verifies the theoretical results. The constructive simulation study, as presented here, explains how people’s interactions shape various social structures in response to environmental conditions. It provides the basic mechanistic explanation for social evolution and integrates microscopic and macroscopic theories in social sciences.

  6. Emergence of kinship structures and descent systems: multi-level evolutionary simulation and empirical data analysis Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    Proceedings of the Royal Society B: Biological Sciences　289　(1969)　2022/02/23

    Publisher: The Royal Society

    DOI： 10.1098/rspb.2021.2641 　

    ISSN： 0962-8452

    eISSN： 1471-2954

  7. Evolution of family systems and resultant socio-economic structures Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    Humanities & Social Sciences Communications　8　(1)　2021/10

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1057/s41599-021-00919-2 　

    ISSN： 2662-9992

    eISSN： 2662-9992

  8. Reply to Read and Parkin: Our model correctly expresses the ethnographic nature of the cultural incest taboo and kinship structures Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    Proceedings of the National Academy of Sciences　117　(17)　9167-9168　2020/04/28

    Publisher: Proceedings of the National Academy of Sciences

    DOI： 10.1073/pnas.2003300117 　

    ISSN： 0027-8424 1091-6490

  9. Evolution of kinship structures driven by marriage tie and competition Peer-reviewed

    Kenji Itao, Kunihiko Kaneko

    Proceedings of the National Academy of Sciences　117　(5)　2378-2384　2020/02/04

    Publisher: Proceedings of the National Academy of Sciences

    DOI： 10.1073/pnas.1917716117 　

    ISSN： 0027-8424 1091-6490

  10. Threshold phenomena with respect to the initiation of depopulation in a simple model of foot-and-mouth disease Peer-reviewed

    Kenji Itao, Fumiya Omata, Yoshitaka Nishikawa, Tetsuro Oda, Toshiharu Sasaki, Cherri Zhang, John Solomon Maninang, Takayuki Yamaguchi

    Mathematical Biosciences and Engineering　16　(5)　5931-5946　2019

    Publisher: American Institute of Mathematical Sciences (AIMS)

    DOI： 10.3934/mbe.2019297 　

    ISSN： 1551-0018

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Research Projects 1

  1. Universality in the Evolution of Family Systems and Social Structures

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for JSPS Fellows

    Institution: The University of Tokyo

    2021/04 - 2024/03