PS 19-171 - Colonial ranching ecology: did environmental variables affect cattle size in the post-Columbian Americas?

Background/Question/Methods

The arrival of the Europeans in the Americas in the early 1500s and new practices associated with their arrival initiated unprecedented environmental in the Western Hemisphere. Among these practices, the development of cattle ranching profoundly contributed to shaping the landscape. Zooarchaeological and osteometric analysis of archaeological cow (Bos taurus) bones from seven sites from the Southeastern USA to Central America, consistently show a high diversity in bovine sizes. It is unclear if this size diversity is due to variations in environmental conditions across the region or to genetic differences between cow morphotypes introduced at different times and places. Our study explores possible associations between cattle sizes inferred through osteometric analysis, and different environmental variables (temperatures, rainfall, altitude) in the regions of study. We provide osteometric data on the variation of cattle size across different regions, sites and chronological phases and use generalized linear mixed models (GLMM) with interactions among temperature / altitude as fixed effects, and site/ phase as random effects. We use the Akaike information criterion (AIC) to select the best fit model to explain cattle size variations.

Results/Conclusions

The environmental variables we consider do not significantly affect the sizes of domestic bovines These results are particularly relevant because, t despite the importance of this industry in the modern times, much remains unknown about the conditions under which cattle ranching was implemented in these different regions. The limited influence of environmental conditions on the growth of early American cattle revealed in this study suggests that the major causes of body size diversity lie in the diverse phylogeographic origins of founding cattle populations in each colony.