{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,3]],"date-time":"2026-06-03T07:07:56Z","timestamp":1780470476850,"version":"3.54.1"},"reference-count":35,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T00:00:00Z","timestamp":1780272000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Ancient human beings started \u201cexternal entropy production\u201d in a late stage of evolution, in addition to the internal entropy production by which energy was dissipated within the body of life, as previously described consistently with the birth of life by maximum entropy production principle. In this paper, the mechanism for development of external entropy production, which is strongly related with the use of tools and controlling fire, is theoretically investigated. Archaeological data show that the brain size of ancient human beings started to rapidly increase around 2.5 million years ago when the usage of tools and control of fire started. It may be natural to assume that the rapid growth of brain size is related to the growth of awareness that helped cooperation with the other human beings for control of fire. Coupled equations for the growth rate of the brain, including awareness, and for the growth rate of the size of the interacting human beings are analyzed. External entropy production per human being, which is directly related to the group size of cooperating human beings, is estimated to increase on a timescale of \u223c20 million years from the beginning after the critical time. This evolution created the coexistence of the internal entropy production of traditional multi-cellular life and the new external entropy production of multi-body life. A psychological problem due to the coexistence of two kinds of entropy production mechanisms in human beings and the concept of technologies based on the present thermodynamic evolution theory are discussed. It is suggested that the evolutionary understanding of the origin of global warming based on external entropy production may be important to create an useful countermeasure.<\/jats:p>","DOI":"10.3390\/e28060621","type":"journal-article","created":{"date-parts":[[2026,6,3]],"date-time":"2026-06-03T06:17:31Z","timestamp":1780467451000},"page":"621","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["External Entropy Production and Human Evolution Toward Multi-Body Life"],"prefix":"10.3390","volume":"28","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2645-1048","authenticated-orcid":false,"given":"Yasuji","family":"Sawada","sequence":"first","affiliation":[{"name":"Division for Interdisciplinary Advanced Research and Education, Tohoku University, Sendai 980-8578, Japan"},{"name":"Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7114-6010","authenticated-orcid":false,"given":"Kenji","family":"Toma","sequence":"additional","affiliation":[{"name":"Division for Interdisciplinary Advanced Research and Education, Tohoku University, Sendai 980-8578, Japan"},{"name":"Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan"},{"name":"Astronomical Institute, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Sawada, Y., Daigaku, Y., and Toma, K. 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