基因的最大值可以改变，但是不要期望它们会很快地改变。位于Natick的军队研究中心高级人类学家Claire C. Gordon保证说90%的新入伍士兵可以很合身地穿上军装，而不需要专门为他们改变衣服的大小。她指出，与篮球队服的情况不同，军装的尺寸已经有很多年没有变化了。如果你为了设计一款新的设备而需要预测人类在不久的将来的身高变化，Gordon认为基本上“你可以采用目前的数据，而且还可以感觉非常自信。”

　　Text 4

　　In 1784, five years before he became president of the United States, George Washington, 52, was nearly toothless. So he hired a dentist to transplant nine teeth into his jaw- having extracted them from the months of his slaves.

　　That’s far different image from the cherry-tree-chopping George most people remember from their history books. But recently, many historians have begun to focus on the roles slavery played in the lives of the founding generation. They have been spurred in part by DNA evidence made available in 1998, which almost certainly proved Thomas Jefferson had fathered at least one child with his slave Sally Hemings. And only over the past 30 years have scholars examined history from the bottom up. Works of several historians reveal the moral compromises made by the nation’s early leaders and the fragile nature of the country’s infancy. More significantly, they argue that many of the Founding Fathers knew slavery was wrong and yet most did little to fight it.

　　More than anything, the historians say, the founders were hampered by the culture of their time. While Washington and Jefferson privately expressed distaste for slavery, they also understood that it was part of the political and economic bedrock of the country they helped to create.