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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 20th 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.”
31. Wilt Chamberlain is
cited as an example to
[A] illustrate the change of height of NBA players.
[B] show the popularity of NBA players in the U.S..
[C] compare different generations of NBA players.
[D] assess the achievements of famous NBA players.
32. Which of the following
plays a key role in body growth according to the text?
[A] Genetic modification.
[B] Natural environment.
[C] Living standards.
[D] Daily exercise.
33. On which of the
following statements would the author most probably agree?
[A] Non-Americans add to the average height of the
nation.
[B] Human height is conditioned by the upright posture.
[C] Americans are the tallest on average in the world.
[D] Larger babies tend to become taller in adulthood.
34. We learn from the last
paragraph that in the near future
[A] the garment industry will reconsider the uniform
size.
[B] the design of military uniforms will remain
unchanged.
[C] genetic testing will be employed in selecting
sportsmen.
[D] the existing data of human height will still be
applicable.
35. The text intends to
tell us that
[A] the change of human height follows a cyclic pattern.
[B] human height is becoming even more predictable.
[C] Americans have reached their genetic growth limit.
[D] the genetic pattern of Americans has altered.
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