Evolutionary Anthropology Lab

Department of Biological Sciences, Graduate School of Science, University of Tokyo

Members | Research | Publications | Conferences | Admissions | Alumni

We study evolution of human behavior from both theoretical and empirical perspectives. One of the biggest questions in science is how humans have acquired the "humanness," or the set of traits that make us feel that we are qualitatively different from the rest of all animals. Although our understandings of phylogenetic and historical details of human beings have been continuously improved, it is still largely unknown why our behavior is so different, as it seems, from that of other animals. To answer this question is to specify the mechanisms by which natural selection has shaped the designs in human behavior. We hope to make some contribution to this ambitious enterprise using mathematical, computational, statistical, and experimental methods. Current research interests are in behavioral ecology of hominins and other animals, evolutionary game theory, cultural evolution, and human mate choice.


Yasuo Ihara
PhD, Lecturer
Application of methods in mathematical biology to evolutionary and biosocial anthropology

Ayaka Onohara
PhD, JSPS postdoctoral fellow
Analysis of language changes in Japanese using mathematical methods including multivariate statistics to determine causes of the changes. I am also interested in phylogenetic analysis of Japanese languages. A combination of these methods might provide a best way to infer language trees.

Masahito Morita
PhD, Project researcher
I am a human behavioral ecologist. My current research examines the evolution of language, from the perspectives of song/music, (non)verbal communication, and child development, especially adolescent sociality. I have also studied fertility decline, reproductive decision-making, parental investment, and engaged in a national birth cohort study (the Japan Environment & Children's Study).

Akiko Matsumoto-Oda
PhD, Visiting researcher, Professor at University of the Ryukyus

Yudai Tokumasu
MSc, Graduate student
Voice perception study in the perspective of Evolutionary psychology.

Yuri Nishikawa
MSc, Graduate student

Takuya Takahashi
MSc, Graduate student, JSPS Research fellow

Akira Handa
BSc, Graduate student

Kyosuke Kubo
BSc, Graduate student

Leonardo Daichi Matsumura

Akari Shimada

Akito Yokoi


Behavioral ecology of hominins and other animals

Male provisioning of offspring and associated pair-based mating systems within multi-male multi-female groups are characteristics of human societies. Paternal care might have emerged in an early stage of hominin evolution and played a unique role in shaping the socioecological niche in which subsequent adaptation took place. We investigated mathematical models for evolution of paternal care and female monogamy to specify the conditions under which various mating systems are predicted (Wakano & Ihara, 2005; Seki et al., 2007; see also Ihara, 2002). Coalition, or coordinated aggression by multiple individuals on a target individual, is observed in primate species. Ihara (2020) evaluated the hypothesis that coalition formation in early hominins may have induced social selection favoring reduced aggression. Seki (2012) explored a hypothetical conflict between autosomal and X-linked genes for sex-specific grandmothering. Kimura & Ihara (2009) studied a model for antagonistic coevolution of male and female traits. Humans are also remarkable in their capacity for social learning (e.g., imitation). Our mathematical and computational models explored how social structure may influence the relative advantages of social learning and individual learning (e.g., trial and error) (Tamura & Ihara, 2012; Tamura et al., 2015). Tamura & Ihara (2011) developed a model for the evolution of simple communication capacities, namely, the capacity for sending a signal and the capacity for receiving it. As for empirical work, Ihara et al. (2016) tested the possibility of socially mediated estrous synchrony or asynchrony in wild anubis baboons (for a related study in chimpanzees see Matsumoto-Oda & Ihara, 2011). Nakahashi et al. (2018) developed a method to obtain "critical interbirth intervals" in hominin species, based on observed age distributions in fossil samples, and argued that the interbirth intervals of early hominins must have already been considerably shortened.

Evolutionary game theory

Evolutionary game theory has become an indispensable tool in the study of human behavior. Of particular interest is the evolution of group-wise cooperation among unrelated individuals. Group-wise cooperation is likely to have been the key adaptation for early humans expanding into the savanna environment, where predation risk was higher and food resources were scarcer. Kurokawa & Ihara (2009) developed a mathematical framework within which to analyze stochastic evolutionary dynamics of n-player games and derived the condition for the emergence of group-wise cooperation in the n-player repeated prisoners' dilemma game as a special case (see also Kurokawa et al., 2010; Kurokawa & Ihara, 2013; Kurokawa & Ihara, 2017; Kurokawa et al., 2018). Ihara (2011) investigated how cooperative behaviors may be affected by a sensitivity to cultural differences among individuals in the context of a hawk-dove game. Tamura et al. (2011) conducted individual-based simulations to study the evolution of punishing behavior from egalitarian motives. Kurokawa (2016) examined the effect of imperfect information in the two-player repeated prisoners' dilemma game considering mistakes in behavior.

Cultural evolution

Culture, as a pool of information transmitted non-genetically between individuals, exhibits evolutionary dynamics; that is, the cultural composition of a population changes over time due to innovation and differential transmission. This process, as an analogue to genetic evolution, is referred to as cultural evolution. Culture has changed the course of human evolution in three ways. First, culture facilitates rapid adaptation to a changing environment. Second, since cultural evolution proceeds semi-independently of genetic evolution, it may result in the spread of novel behavior not expected by a conventional model of genetic adaptation. Third, culture provides a new environment to which genetic adaptation may occur and thus a possibility of gene-culture coevolution. Ihara (2008) developed a mathematical model to describe a possible dynamics of maladaptive cultural evolution (see also Ihara & Feldman, 2004; Kendal et al., 2005). Seki & Ihara (2012) investigated the rate of cultural change considering stochastic evolutionary dynamics. Takahashi & Ihara (2019) analyzed the cultural and evolutionary dynamics involving payoff-biased social learning when cultural variants are associated with stochastic payoffs. Takahashi & Ihara (2020) developed a model to describe spatial patterns of dialect words spreading from a cental population to peripheries. Tamura (2014) documented homogamy for birthplaces in Japan, which may serve to maintain cultural variation within regions. Lee (2015) attempted to reconstruct the evolutionary history of the Koreanic language, using methods adopted from evolutionary biology (for a related work see Lee & Hasegawa, 2014). Tamura & Ihara (2017) analyzed demographic data to study the cultural evolution of the "hinoeuma" superstition in Japan.

Human mate choice

Animals do not mate at random. Mate choice directly affects the reproductive output of individuals being chosen and thus can have a profound effect on the evolution of morphology and behavior of species. Sexual selection by mate choice may have also played a significant role in shaping human behavior. Nojo et al. (2011) studied the relationship between facial resemblance and attractiveness in rural Indonesia. Nojo et al. (2012) investigated homogamy in facial characteristics among Japanese people and a possible role played by a sexual-imprinting-like mechanism. Seki et al. (2012) collected data on body stature in Japanese to examine the possibility of homogamy and sexual-imprinting-like effect for height. We also used computer simulations to examine the sexual selection hypothesis for the emergence and maintenance of phenotypic diversity among human populations (Nojo & Ihara, 2019).

Recent publications

Takahashi T, Ihara Y, 2020. Quantifying the spatial pattern of dialect words spreading from a central population. Journal of the Royal Society Interface 17, 20200335.

Ihara Y, Ikeya K, Nobayashi A, Kaifu Y, 2020. A demographic test of accidental versus intentional island colonization by Pleistocene humans. Journal of Human Evolution 145, 102839.

Ihara Y, 2020. A mathematical model of social selection favoring reduced aggression. Behavioral Ecology and Sociobiology 74, 91.

Morita M, 2019. Behaviours of dyads sitting outside in New York's Times Square: exploratory observation using webcam videos. Journal of Human Ergology 48, 69-81.

Takahashi T, Ihara Y, 2019. Cultural and evolutionary dynamics with best-of-k learning when payoffs are uncertain. Theoretical Population Biology 128, 27-38.

Morita M, 2019. Human behavioral ecology. In "Encyclopedia of Evolutionary Psychological Science" (Shackelford T, Weekes-Shackelford V editors). Springer, Cham.

Nojo S, Ihara Y, 2019. The effect of sexual selection on phenotypic diversification among human populations: A simulation study. Journal of Theoretical Biology 462, 1-11.

Kurokawa S, Wakano JY, Ihara Y, 2018. Evolution of group-wise cooperation: generosity, paradoxical behavior, and non-linear payoff functions. Games 9, 100.

Nakahashi W, Horiuchi S, Ihara Y, 2018. Estimating hominid life history: the critical interbirth interval. Population Ecology 60, 127-142.

Kurokawa S, Ihara Y, 2017. Evolution of group-wise cooperation: Is direct reciprocity insufficient? Journal of Theoretical Biology 415, 20-31.

Tamura K, Ihara Y, 2017. Quantifying cultural macro-evolution: a case study of the hinoeuma fertility drop. Evolution and Human Behavior 38, 117-124.

Kato A, Morita K, 2016. Forgetting in reinforcement learning links sustained dopamine signals to motivation. PLOS Computational Biology 12, e1005145.

Ihara Y, Collins DA, Oda R, Matsumoto-Oda A, 2016. Testing socially mediated estrous synchrony or asynchrony in wild baboons. Behavioral Ecology and Sociobiology 70, 1921-1930.

Kurokawa S, 2016. Does imperfect information always disturb the evolution of reciprocity? Letters on Evolutionary Behavioral Science 7, 14-16.

Lee S, 2015. A sketch of language history in the Korean peninsula. PLOS ONE 10, e0128448.

Ihara Y, 2015. Human mate choice. pp.335-339 in "International Encyclopedia of the Social & Behavioral Sciences 2nd edition" (Wright JD editor-in-chief) 11. Elsevier, Oxford.

Tamura K, Kobayashi Y, Ihara Y, 2015. Evolution of individual versus social learning on social networks. Journal of the Royal Society Interface 12, 20141285.

Recent conference activities

Tokumasu Y. How is sexual difference constructed, and what does it construct? ALE (Adolescence x Language Evolution). The University of Tokyo, Tokyo, 5 July 2019.

Morita M. Exploring socioecological foundations for the evolution of language: observation of communication in a natural setting using webcam videos. The 14th Annual Conference of European Human Behaviour and Evolution Association. Toulouse, 23-26 April 2019.

Ihara Y. When and why language emerged. Tokyo Lectures in Evolinguistics 2019. The University of Tokyo, Tokyo, 11-13 March 2019.

Ihara Y. Cultural phylogeny and diffusion. The (co-)evolution of genes, languages, and music from data analyses to theoretical models. Yokohama City University Kihara Institute for Biological Research, Yokohama, 17 Jul 2018.

Nakahashi W, Horiuchi S, Ihara Y. Hominid interbirth interval and evolution of paternal care. 2018 Annual Meeting of the Society for Mathematical Biology & the Japanese Society for Mathematical Biology. The University of Sydney, Sydney, 8-12 July 2018.

Ihara Y, Kaifu Y. Dispersal to islands by the Pleistocene humans: evaluating alternative scenarios. The 1st AsiaEvo Conference. Sheraton Dameisha Resort, Shenzhen, 18-20 April 2018.

Ihara Y. Evolution of physical weakness by social selection through choice of collaborative partners. Kyoto Conference on Evolinguistics. Kyoto University, Kyoto, 11-12 November 2017.

Tamura K, Ihara Y. Quantifying cultural macro-evolution: A case study of the hinoeuma fertility drop. Inaugural Cultural Evolution Society Conference. Max-Planck Institute for the Science of Human History, Jena, 13-15 September 2017.

Ihara Y. An introduction to mathematical modeling in evolutionary archaeology. Perspectives on Prehistoric Cultural Evolution: From Archaeology to Behavioral Experiment, AP Shinagawa, Tokyo, 7-8 August 2017.


For all students

Prospective students are required to take an entrance exam (given in the Japanese language) to Department of Biological Sciences (see here).

For overseas students

For qualified students with overseas education, the score of the GRE Subject Tests may be accepted in lieu of the entrance exam. Department of Biological Sciences requires the GRE subject score of Biology (see here). The University of Tokyo provides international students with access to a number of financial aid options (see here).

Former members

Kotaro Aizawa, Kenichi Aoki, Emily Emmott, Naoki Hatanaka, Mika Igarashi, Ayaka Kato, Mariko Kimura, Yutaka Kobayashi, Satoshi Komori, Shun Kurokawa, Mai Kuroshima, Sean Lee, Yuki Mizusaki, Saori Nojo, Kento Orihara, Motohide Seki, Satoshi Sekiguchi, Kohei Tamura, Satoshi Tamura, Tasuku Toyama, Mariko Tsumaki, Shusuke Yamashita, Taro Yoshida

PhD in 2019

Saori Nojo (National Institute of Technology, Kisarazu College)

PhD in 2013

Shun Kurokawa (University of Tokyo)

Kohei Tamura (Tohoku University)

PhD in 2012

Motohide Seki (Kyushu University)

Evolutionary Anthropology Lab

Department of Biological Sciences
Graduate School of Science
The University of Tokyo
Hongo 7-3-1, Bunkyoku
Tokyo 113-0033, Japan

Recent and forthcoming events

5 August 2020
An article by Yasuo Ihara and co-authors was featured in UTokyo FOCUS.

9 April 2020
Kohei Tamura's (Tohoku University) book "Mathematics of Cultural Evolution" was published.

23 March 2020
Mika Igarashi was awarded a MSc for her thesis "A simulation analysis on the within-population diversity and innovation."

10 February 2020
Damián Blasi (Harvard University) gave a seminar "Rethinking linguistic diversity: when, how and why languages change."

29 November 2019
Kohei Tamura (Tohoku University) discussed what it is like to be a university professor today and the future of Japanese universities.

20 November 2019
A children's book about language and mind (edited by K. Okanoya and illustrated by Y. Noda) was published.

11 November 2019
Takenori Takada (Hokkaido University) gave a seminar on the history of demographic theory in biology.

27 September 2019
Akiko Uchida (Waseda University) talked about Turkana Basin Institute and human evolution research in Turkana, Kenya.

5 July 2019
ALE (Adolescence x Language Evolution), an opening symposium for a UK-Japan collaboration (organized by M. Morita, Y. Tokumasu, and Y. Ihara)

4 July 2019
TEA (Think & Exchange ideas of Adolescence), a workshop for a UK-Japan collaboration on adolescent sociality (organized by E. Emmott and M. Morita)

10 June 2019
Saori Nojo was awarded a PhD for her thesis "Effect of mate choice on between-population phenotypic differentiation."

5 June 2019
Andrew R. Timming (University of Western Australia) gave a talk on"Human resource management and evolutionary psychology."

29 May 2019
Risa Teramoto (Kyoto University) talked about her study on mating behaviors in Kgatla agro-pastoralists in Botswana.

29 March 2019
A farewell party for Naoki Hatanaka, Kento Orihara, Satoshi Sekiguchi, and Taro Yoshida

25 March 2019
Kento Orihara was awarded a MSc for his thesis "A theoretical study on the effect of ecocultural factors on gut microbiota."

11-13 March 2019
Tokyo Lectures in Evolinguistics 2019, a three-day session featuring eight lectures on language evolution, took place in Tokyo.

19 February 2019
Yuri Nishikawa was awarded an Incentive Award for his poster presentation "Cultral evolution of folk songs in the Ryukyu Islands and its relationship with dialects and genes" in the 3rd Meeting of the Evolinguistics project.

5 February 2019
Satoru Kiire (University of Tokyo) gave a talk about evolutionary approaches to human psychology, including his work on physical attractiveness and personality.

7 December 2018
Akiko Matsumoto-Oda (University of the Ryukyus) talked about predation on baboons and its implications to anti-predatory behavior in early hominins.

26 October 2018
Noa Nishimoto (Kyoto University) gave a seminar entitled "Number sense and grammatical categories of number."

22 October 2018
A new book about a dialogue between processual and post-processual archaeology (K. Akoshima and K. Mizoguchi eds., Keiso Shobo), to which Yasuo Ihara gives a foreword, was released.

28 September 2018
Hiromi Matsumae (Tokai University) talked about her study on linguistic diversity from genetic and evolutionary perspectives.

4 September 2018
Emily Emmott (University College London) gave a seminar "Cooperative breeding in developed populations: A UK case study."

1-9 August 2018
Evolinguistics 2018, a series of seven symposia/conferences on language evolution, took place in Tokyo and Kyoto.

28 May 2018
A book on evolutionary psychology (Japanese translation supervised by K. Hiraishi, T. Hasegawa, T. Matoba, University of Tokyo Press), in which Yasuo Ihara writes a short essay, was published.

9 May 2018
Aru Toyoda (Kyoto University) gave a talk on the reproductive ecology in stump-tailed macaques.

22 March 2018
Takuya Takahashi was awarded a MSc for his thesis "Evolution of the learning strategy that acquires cultural traits with a stochastic payoff."

7 March 2018
A farewell party for Tasuku Toyama

5 January 2018
Kiyoshi Tadokoro (Akita University) talked about New Guinean ethnography and the study of cultural evolution in cultural anthropology.

10 December 2017
Saori Nojo was awarded the Young Researcher Award for her oral presentation "The effect of mate choice on phenotypic differentiation among populations" (coauthored by Y. Ihara) at the 10th Annual Meeting of Human Behavior and Evolution Society of Japan.

24 November 2017
Masahito Morita (Kyoto University) gave a seminar on evolutionarily maladaptive behaviors in humans.

4 November 2017
Kento Orihara was awarded the 2nd place in the Best Poster Award at the 71st Annual Meeting of Anthropological Society of Nippon for his presentation "A simulation study on factors affecting patterns of diversity in gut microbiota" (coauthored with Y. Ihara).

20 October 2017
Joe Y. Wakano (Meiji University) talked about "Ecocultural range-expansion scenarios for the replacement or assimilation of Neanderthals by modern humans."

19/24 September 2017
Opening conferences of the project "Evolinguistics: Integrative Studies of Language Evolution for Co-creative Communication" (head invesitigator: K. Okanoya) were held in Kyoto (19 Sep) and Tokyo (24 Sep).

9 August 2017
A new book on "Cultural Evolution and Archaeology" (H. Nakao, T. Matsugi, N. Minaka eds., Keiso Shobo), to which Yasuo Ihara contributes a chapter, was released.

7-8 August 2017
A symposium on "Perspectives on Prehistoric Cultural Evolution: From Archaeology to Behavioral Experiment" (organized by K. Tamura, Y. Ihara, and H. Nakao) was held in Tokyo.

2 June 2017
Keiichi Omoto (the University of Tokyo and International Research Center for Japanese Studies) gave a lecture entitled "From DNA to Human Rights: Toward a New Synthesis of Anthropology."

31 March 2017
A farewell party for Ayaka Kato and Yuki Mizusaki

23 March 2017
MScs were awarded to Ayaka Kato for her thesis "Reassessing evolutionary dynamics of learning strategy using reinforcement learning model" and to Tasuku Toyama for his thesis "Mathematical analysis on evolution of retrieval tactics, cooperative transport by ants."

16 March 2017
Tomomi Nakagawa (Okayama University) gave a seminar on skeletal evidence of violence in the Jomon and Yayoi periods of Japan.

11 December 2016
Ayaka Onohara was awarded the Young Researcher Poster Award for her presentation "Effect of population size on the gain/loss rates of lexical and grammatical items" (coauthored with Y. Ihara) at the 9th Annual Meeting of Human Behavior and Evolution Society of Japan.

16 October 2016
Ayaka Onohara was awarded the Poster Session Award for her presentation "Environmental and social factors associated with the gain or loss rate of language change" at the 25th Conference of GIS Association of Japan.

14-17 September 2016
A trip to Hachijojima

22 June 2016
Kyoko Yamaguchi (Liverpool John Moores University) talked about her study on genetics of human visible traits.

13 June 2016
Mikihiko Wada (Hosei University) gave a talk on the evolution of law.

15 April 2016
Kenichi Aoki (Meiji University) gave a talk on "RNMH and a mathematical theory of Palaeolithic culture."

8 April 2016
Shun Kurokawa (Kyoto University) gave a talk on "The evolution of generosity and paradoxicalness in sizable groups."

30 March 2016
A farewell party for Kotaro Aizawa and Sean Lee

24 March 2016
Kotaro Aizawa was awarded a MSc for his thesis "A study about a novel cooperation strategy 'out-group homegeneity' in the repeated prisoner's dilemma, by computer simulation and mathematical analysis."