Bernard Bailyn has recently reinterpreted the early history of the United States by applying new social research findings on the experiences of European migrants. In his reinterpretation, migration becomes the organizing principle for rewriting the history of pre-industrial North America. His approach rests on four separate propositions.
The first of these asserts that residents of early modern England moved regularly about their countryside.- migrating to the New World was simply a "natural spillover". Although at first the colonies held little positive attraction for the English they would rather have stayed home--by the eighteenth century people increasingly migrated to America because they regarded it as the land of opportunity. Secondly, Bailyn holds that, contrary to the notion that used to flourish in American history textbooks, there was never a typical New World community. For example, the economic and demographic character of early New England towns varied considerably.
Bailyn’s third proposition suggests two general patterns prevailing among the many thousands of migrants: one group came as indentured servants, another came to acquire land. Surprisingly, Bailyn suggests that those who recruited indentured servants were driving forces of transatlantic migration, These colonial entrepreneurs helped determine the social character of people who came to pre-industrial North America. At first, thousands of unskilled laborers were recruited: by the 1730’s, however, American employers demanded skilled workers.
Finally, Bailyn argues that the colonies were a half-civilized hinterland of the European culture system. He is undoubtedly correct to insist that the colonies were part of the Anglo-American empire. But to divide the empire into English core and colonial periphery, as Bailyn does, devalues the achievements of colonial culture. It is true, as Bailyn claims, that high culture in the colonies never matched that in England. But what of seventeenth-century New England, where the settlers created effective laws, built a distinguished university, and published books Bailyn might respond that New England was exceptional. However, the ideas and institutions developed by New England Puritans had powerful effects on North American culture.
Although Bailyn goes on to apply his approach to some thousands of indentured servants who migrated just prior to the revolution, he fails to link their experience with the political development of the United States. Evidence presented in his work suggests how we might make such a connection. These indentured servants were treated as slaves for the period during which they had sold their time to American employers. It is not surprising that as soon as they served their time they gave up good wages in the cities and headed west to ensure their personal independence by acquiring land. Thus, it is in the west that a peculiarly American political culture began, among colonists who were suspicious of authority and intensely anti-aristocratic.
It can be inferred from the text that American history textbooks used to assert that（）
A.many migrants to colonial North America were nor successful financially
B. New England communities were much alike in terms of their economics and demographics
C. many migrants to colonial North America failed to maintain ties with their European relations
D. the level of literacy in New England communities was very high
请根据科学家的研究解释椒花蛾黑化现象：