A morphological and chemo-taxonomic approach to characterize starches from plants potentially available in the Eurasian Steppe during MIS 3 (60-25 ka BP)

Plants are often underrepresented in archaeological reconstructions of past subsistence strategies, especially concerning the Paleolithic, largely because they preserve poorly in the archaeological record. However, plants are versatile resources that were used for a wide range of purposes, including as a crucial food source. Starch, a high-energy polysaccharide produced by plants, may have played an important role in the survival of Homo sapiens as they dispersed into the northern latitudes of Eurasia during Marine Isotopic Stage 3 (MIS 3, 60–25 ka BP). Starch granules provide direct evidence of the consumption and intentional elaboration of starchy plants. The presence of these residues alongside use-wear traces strongly suggests the deliberate exploitation of plants through mechanical processing, shedding light on early human adaptation strategies.The conventional approach to starch grain identification relies on optical microscopy under transmitted and polarized light to detect key diagnostic features, and typically, morphological assessment is supported by comparison with modern reference collections. However, the majority of datasets prioritize economically important domesticated plants, leaving starches from wild plants available during MIS 3, particularly at boreal latitudes, largely underrepresented.This study comprehensively analyzes starch extracted from 26 plant taxa. To this end, an array of physicochemical characterization techniques was integrated, including optical microscopy, scanning electron microscopy, laser granulometry, infrared spectroscopy, and gas chromatography-mass spectrometry. This innovative approach facilitates the identification of starch grains that are comparable to those recovered from ground stone tools at Upper Paleolithic sites across Eurasia, offering a more complete framework for archaeological interpretation.