考研英语阅读命题思路透析和真题揭秘(61)

In the early 1960s Wilt Chamberlain was one of only three players in the National Basketball Association (NBA) listed at over seven feet. If he had played last season, however, he would have been one of 42. The bodies playing major professional sports have changed dramatically over the years, and managers have been more than willing to adjust team uniforms to fit the growing numbers of bigger, longer frames.

The trend in sports, though, may be obscuring an unrecognized reality: Americans have generally stopped growing. Though typically about two inches taller now than 140 years ago, today's people- especially those born to families who have lived in the U.S. for many generations- apparently reached their limit in the early 1960s. And they aren't likely to get any taller. "In the general population today, at this genetic, environmental level, we've pretty much gone as far as we can go," says anthropologist William Cameron Chumlea of Wright State University. In the case of NBA players, their increase in height appears to result from the increasingly common practice of recruiting players from all over the world.

Growth, which rarely continues beyond the age of 20, demands calories and nutrients - notably, protein - to feed expanding tissues. At the start of the 20^th century, under-nutrition and childhood infections got in the way. But as diet and health improved, children and adolescents have, on average, increased in height by about an inch and a half every 20 years, a pattern known as the secular trend in height. Yet according to the Centers for Disease Control and Prevention, average height- 5′9〞 for men, 5′4〞for women- hasn't really changed since 1960.

Genetically speaking, there are advantages to avoiding substantial height. During childbirth, larger babies have more difficulty passing through the birth canal. Moreover, even though humans have been upright for millions of years, our feet and back continue to struggle with bipedal posture and cannot easily withstand repeated strain imposed by oversize limbs. "There are some real constraints that are set by the genetic architecture of the individual organism," says anthropologist William Leonard of Northwestern University.

Genetic maximums can change, but don't expect this to happen soon. Claire C. Gordon, senior anthropologist at the Army Research Center in Natick, Mass., ensures that 90 percent of the uniforms and workstations fit recruits without alteration. She says that, unlike those for basketball, the length of military uniforms has not changed for some time. And if you need to predict human height in the near future to design a piece of equipment, Gordon says that by and large, "you could use today's data and feel fairly confident."

20世纪60年代早期，Wilt Chamberlain 是美国国家篮球协会（NBA）中仅有的三个身高超过7英尺的球员之一。可是如果他参加了上个赛季的比赛，那他就是42个如此之高的球员之一了。近几年那些身体状况起到主要作用的职业运动都经历了巨大的变化，这些运动的经理人们都非常乐意重新裁制队服以适应球员们更高、更大的身材。

但是，运动领域的这个趋势有可能掩盖了一个没有被承认的现实：即从总体上来说，美国人已经停止了长高。尽管现在人们比起140年前明显长高了2英寸，但是他们--尤其是那些出生在移民美国许多代的家庭中的人们--很显然在20世纪60年代的时候就已经达到了他们身高的极限。他们已经不可能再长高了。"在目前的基因环境下，总体人口已经长到了我们能够达到的程度"，Wright State 大学的人类学家William Cameron Chumlea说道。而对于NBA球员来说，他们身高增长的原因主要在于现在从全球招募球员已经成为了一种普遍的做法。

身高的增长一般在20岁以后就停止了，长高需要热量和营养物质--主要是蛋白质--以供应身体组织的扩展。在20世纪初的时候，营养不良和儿童疾病影响了人们身体的长高。但是随着饮食和健康状况的改进，儿童和青少年比20年前平均长高了约一个半英寸，这就是众所周知的身高世俗趋势。但是，疾病控制和预防中心认为自从20世纪60年代以来，人们的平均身高--男性5英尺9英寸，女性5英尺4英寸--并没有发生很大的变化。

总的来说，防止身材过高有着很大的优势。在产妇分娩的过程中，个子大的孩子通过产道的困难更大。此外，尽管人类直立行走已达百万年之久，我们的脚和背总是很费劲地保持两足姿势、而且很难抵挡过大的身材带来的巨大压力。"每种生物的基因结构中都有一些限制。"西北大学的人类学家William Leonard说。

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。"