In the mid- to late-eighteenth century, a theory emerged among some European intellectuals that the New World landmasses were inherently inferior to Europe. The so-called "degeneracy thesis" held that climatic extremes, humidity and other atmospheric conditions in America physically weakened both men and animals.
Two authors, James W. Ceaser and Philippe Roger, have interpreted this theory as "a kind of prehistory of anti-Americanism." Purported evidence for the idea included the smallness of American fauna, dogs that ceased to bark, and venomous plants; one theory put forth was that the New World had emerged from the Biblical flood later than the Old World. Native Americans were also held to be feeble, small, and without ardor.