For a little while now, I have been interested in identifying and explaining changes in the size of domestic livestock in the 14th century. This research was originally inspired by my analysis of the animal remains from Dudley Castle, West Midlands, UK, which revealed a statistically-significant increase in the size of cattle, sheep, pig, and even chicken, between two phases of occupation (1262-1321 and 1321-1397). These changes were much earlier than those documented at other sites (mostly 15th-17th century), and I interpreted them within the context of altered tenurial and agricultural practices in the wake of the Black Death: Thomas, R. 2005. Zooarchaeology, improvement and the British Agricultural Revolution. International Journal of Historical Archaeology 9 (2): 71-88.
Since then, a number of additional sites have provided evidence of livestock size change in the 14th century - seemingly adding weight to this idea. Just recently, however, I have completed a collaborative project exploring size change in domestic livestock in medieval and early modern England, using data from London: Thomas, R., Holmes, M., and Morris, J. 2013. “So bigge as bigge may be”: tracking size and shape change in domestic livestock in London (AD 1220-1900). Journal of Archaeological Science 40 (8): 3309-3325.
In this study, we analysed 7966 individual cattle, sheep, pig and chicken bone measurements from 105 sites excavated in London dating to the period AD 1220–1900 and multiple episodes of size change were identified. The earliest evidence for size change in cattle and sheep occurs in the early 14th century: this is earlier than any previously documented instance of livestock size increase in the medieval period. The fact that only cattle and sheep witness size increase is interesting, given the major outbreaks of disease affecting these animals in the first quarter of the 14th century: sheep murrain was epidemic between 1314 and 1316, while a panzootic in cattle occurred between 1319 and 1322. Given the timing of the size increases and the fact that only cattle and
sheep are affected, re-stocking policies might be an obvious explanation. However, selective breeding from larger animals was probably not the cause: there is no zooarchaeological evidence for large livestock elsewhere in England and Wales in this period and the large-scale transnational cattle trade did not commence until the late 15th century. Perhaps, a temporary relative increase in mean size may have
occurred in the archaeological (death) assemblage, because of relatively lower slaughter rates of female cattle following the pestilence. This might be explained by the
fact that the slaughtering of females, which survived the panzootic, might have been delayed, to re-populate the herds; consequently, survivors were used for a longer period than would have normally been the case. Alternatively, the larger size of cattle and sheep may reflect the actions of natural selection. It is entirely conceivable that smaller, weaker animals were more susceptible to malnutrition and ultimately mortality, while the larger, healthier animals survived to perpetuate their genes.
At the moment I am fairly open about the most likely explanation, but I would welcome any thoughts if you have any.