Domestication of wild cattle, sheep, and pigs began a process of body size diminution. In most of Western Europe this process continued across prehistory and was not reversed until the Roman period. However, in Italy, an increase in livestock body size occurred during the Iron Age, earlier than the Western provinces. In order to better understand the nature and timing of this early increase in animal size, this paper presents a detailed regional study of taxonomic abundance and biometric data from zooarchaeological assemblages recovered from the Po and Venetian-Friulian Plains in northern Italy. Our results demonstrate a high level of regionality in the choice of species exploited, with husbandry systems focused on different domesticates, as well as regional differences in animal size. However, despite significant variation in species frequencies, settlement structure, and epigraphic tradition, all areas with sufficient data demonstrate similar significant changes in livestock body size. Cattle and sheep increased incrementally in size prior to the Roman conquest in all regions considered; surprisingly, pigs continued to decrease in size throughout later prehistory. The incremental pace and pan-regional character of the size change in cattle and sheep suggests an internally motivated phenomenon rather than herd replacement with a new larger population, as might follow colonisation or conquest. The divergence in size trends for bovids and suids suggests a noteworthy change in cattle and sheep herding practices during the Iron Age or final centuries of the Bronze Age, in contrast with greater continuity in pig management. Our analysis provides a thorough zooarchaeological synthesis for northern Italy and, for the first time, demonstrates that both cattle and sheep increased in size outside of Roman territory well before the conquest of this area. This study offers a basis for future chemical analyses (DNA, isotopes), which will further investigate the cause(s) of livestock size changes in northern Italy
