Research

Breastfeeding and weaning in human evolution

Using stable isotope analysis and mathematical modeling, I have been investigating the breastfeeding and weaning patterns of ancient human populations and extant primates, and how these patterns have affected their reproductive strategies and population dynamics (Tsutaya & Yoneda 2015 Yearb Phys Anthropol). I have been focusing on this theme mostly during my doctoral and early postdoctoral periods. I have revealed some aspects of the population dynamics of Jomon hunter-gatherers (Tsutaya et al. 2016 J Archaeol Sci) and premodern townspeople in Japan (Tsutaya et al.  2014 Am J Phys Anthropol; 2019 Am J Phys Anthropol) from the weaning patterns of these ancient human skeletal populations. I also shed light on the social issues of contemporary breastfeeding and weaning from the perspective of human evolution (Tsutaya & Mizushima 2023 Yearb Biol Anthropol).

Primate ecology

Together with colleagues of Japan Orangutan Research Center, I am conducting ecological research on wild orangutans in Danum Valley Conservation Area in Sabah, Malaysian Borneo. I am interested in the diet and breastfeeding of orangutans and have applied stable isotope analysis (Tsutaya et al. 2022 Am J Biol Anthropol). I am also conducting research on captive individuals (Tsutaya et al. 2017 Rapid Commun Mass Spectrom; 2021 Primates).

In addition to orangutans, I also study other great apes, such as chimpanzees and bonobos, by using stable isotope analysis and proteomics

Proteomics in ecology and evolution

I am applying high-throughput mass spectrometry-based proteomics to archaeology, ecology, and paleontology (e.g. palaeoproteomics). Palaeoproteomics is my main focus at this moment. So far, I have investigated the interaction between humans and oral bacteria in the past  (Uchida-Fukuhara et al. 2024 Sci Rep) and clarified the circumstances at the time of death of ancient animal individuals (Tsutaya et al. 2019 Sci Rep). I have also developed and applied a new method "fecal proteomics" for reconstructing the behavior and physiological state of terrestrial mammals (Tsutaya et al. 2021 Mol Ecol Resour).

Ongoing research includes reconstructing the phylogeny of fossil hominins (Tsutaya et al. 2025 Science), reconstructing the evolutionary history of fauna on the Japanese archipelago, using ZooMS to identify fragmented bones, reconstructing the life histories of living primates, and developing ancient environmental proteomics.

Other

As a member of the collaborative research group “Harassment in Fieldwork (HiF)”, I am conducting a survey on the sexual violence and sexual harassment encountered by fieldwork researchers.

I am also interested in conservation paleobiology, that is the application of archaeological or paleontological knowledge to modern conservation ecology (Tsutaya et al. 2022 Quat Int).

Releases

I have issued the following press releases and articles to provide explanations of research results.

• A male Denisovan jawbone from Taiwan expands the known geographic range of this extinct human group | University of Copenhagen

• Diverse diets of civets in Borneo rainforest allow them to live in same geographical area | Hiroshima University

• Studying ape faeces can explain why humans breastfeed for such a short time | Science News

• Post-Weaning Diet In Archaeological Human Populations | Science Trends