This research has been developed as part of the RAINDROPS Research Project, funded by the European Research Council (ERC) under the Horizon 2020 framework (ERC-Stg 759800). The studied sites were excavated by the Eastern Tigrai Archaeological Project (ETAP), funded by the Social Sciences and Humanities Research Council of Canada (SSHRC Insight Grant #435-2014-0182 and Partnership Development Grant #890-215-003). We are also grateful for the participation of the Ethiopian Authority for Research and Conservation of Cultural Heritage (ARCCH) and the Tigrai Tourism and Cultural Commission (TCTB). We wish to acknowledge Carlos Santiago-Marrero and Francesca D'Agostini for their help during the phytolith and starch analyses, Elizabeth Peterson and Lynn Welton for assistance with interpretations of site Mezber and Ona Adi contexts and Shannon Wood who completed site mapping. Finally, we are grateful to all the people who have participated in ETAP research at Mezber and Ona Adi since 2007, specially to the local communities near Mezber and Ona Adi for their collaboration in the archaeological and ethnoarchaeological fieldwork.

This repository contains the supplementary information of the article entitled "On the verge of domestication: early use of C4 plants in the Horn of Africa" published in the journal Proceedings of the National Academy of Sciences (https://www.pnas.org/doi/10.1073/pnas.2300166120)