"Two tribes": Handaxe shape variation shows distinct regional cultural groups in southeastern Britain between 424 000 and 374 000 BP

ABSTRACT This paper examines regional and chronological variations in Acheulean handaxe morphology during Marine Isotope Stage 11 (c. 425–365 ka BP) in Britain. Using a data set of 737 handaxes from 13 securely dated sites in East Anglia and the Thames Valley, we apply three‐dimensional geometric morphometric analysis to examine morphological variability. Our results show that two distinct handaxe forms were present in different areas of Britain during MIS 11: sub‐stage MIS 11c assemblages in East Anglia are dominated by ovate handaxes with twisted edges, while contemporaneous Thames Valley assemblages are characterised by pointed forms. By sub‐stage MIS 11a, Thames Valley sites shift to ovate handaxes with twisted edges, whereas East Anglia now shows a predominance of pointed forms. Statistical models indicate that rather than raw material constraints or reduction intensity, regional factors such as cultural groups drive these differences. These patterns suggest persistent technological norms, strong knowledge transmission and cultural resilience across climatic oscillations. Our findings highlight the role of small‐scale, juxtaposed cultural groups in shaping Acheulean variability and adapting to dynamic Middle Pleistocene environments.