.

In Plagues and Peoples historian William McNeill crosses a boundary between medicine and sociology to trace the fascinating evolution of what he calls macroparasites. "A conqueror could seize food from those who produced it, and by consuming it himself become a parasite of a new sort on those who did the work. In specially fertile landscapes it even proved possible to establish a comparatively stable pattern of this sort of macroparasitism among human beings".

Land economist Colin Clark has calculated that stability is reached when the macroparasites consume about 50 percent of product in the form of land rent or other obligations. Feudal obligations, for example, might include military service on behalf of the lord of the manor. The caste system, which has existed for thousands of years, relegates different strata of society to menial tasks, some of these being pretty close to slavery. But these macroparasitic systems continue to reinvent themselves, as in the agricultural support schemes that protect European landowning elites, and in the following example from Lappe and Collins, Food First:

"The buyers are a motley group, some connected with land through family ties, some altogether new to agriculture. A few have unemployed rupees acquired through undeclared earnings, and most of them look upon farming as a tax haven, which it is, and as a source of earning tax-free supplementary income.

The medical doctor from Jullundar who turned part time farmer is sitting pretty. The 15 acres he purchased four years ago have tripled in value. To listen to him, he is farming 'for the good of the country'. His only vexation is whether or not he will succeed in buying another ten acres he has his eyes on - and what a disappointed man he will be if they escape him. As we watched him supervise the threshing, he was anything but a gentleman farmer."