If an occupation census had been taken in the elh century，it would probably have revealed that quite 90%of the people were country dwellers who drew their livelihood from farming，herding，fishing，or the forest．An air photograph taken at that time would have revealed a sprinkling of villages，linked together by un—suced roads and more than 10，000 persons．A second picture，taken in the mid—fourth century would show that the villages had grown larger，more numerous，and also more widespread，for Europeans had pushed their frontier outward by clearing，draining，and settling new areas．There would be more people on the road，rivers and seas，carrying food or raw materials to towns which had increased in number，size and importance． But a photograph taken about 1450 would reveal that little further expansion had taken place during the preceding hundred years．
Any attempt to describe the countryside during those centuries is beset by two difficulties．In the first place we have to examine the greater part of Europe’s 3,50,000 square miles，and not merely the Mediterranean lands．In the second place the inhabitants of that wide expanse refuse to fit into one standard pattern or to stand still． There is variety and there is change．①Consequently, as a distinguished student of medieval rural life once remarked, "In the history of land problems, there is no sin like the sin of generalization" and "There is no heresy about the Middle Ages quite so pernicious(有害的)as the theory that they were unchanging."
In the early days of studying economic history it was customary to describe a "typical" manor and give the impression that all rural life was of this kind. But a vast amount of research has been done since then, for the field is an interesting one, the documents are abundant in some countries, the work calls for great patience and skill, and the results may be revolutionary. From such arduous (辛勤的) labor Professor Eileen Power emerged with the conclusion that "manor" was a term about as descriptive as the word "mammal". ②After equally arduous effort Professor Kosminsky defined the manor as a community in which unfree villagers (villains, serfs")cultivated their lord’s domain as the price of their serfdom and of their use of a holding of land. He then discovered that even in the English midlands, the stronghold of manors, only about 60% of the territory was "manorial" in 1279. The remaining 40% was non-manorial; it had no unfree tenants, or it had no domain, or it was all domain and had no villain holdings. In France and other continental regions research is revealing similar diversity. After reading a recent study of the seigniorial (领主的) system in Lorraine, one reviewer threw up his hands and exclaimed, "The more we look at things, the more they appear complicated.\
It is implied in the passage that the findings made in the study concerning economic history may be ______.