Why Americans Are Tall, But
Have Stopped Growing Taller
3 — There was a time when most American children were expected to outgrow
data on Americans' average height was first collected in the early 20th century,
children and adolescents grew about an inch and a half taller every 20 years.
But recent measurements suggest Americans' average height has more or less hit
collected from the federal Centers for Disease Control show that average height
for Americans has stabilized in the past 50 years to about 5 feet 9 inches for
men and 5 feet 4 inches for women.
pretty well maxed out in terms of stature. There's been little change in adult
height over last generation," says William Leonard, an anthropologist at
Are What You Eat
reason, explains Leonard, is most Americans now face few nutritional or health-related
stresses in their youth. People grow most as infants and then as adolescents,
and most Americans have avoided disease and eaten enough meat and milk in their
youth to reach their genetic height potentials.
Leonard is quick to point out that while overall U.S. height averages have more
or less stabilized, there are small pockets of the population where slight increases
in height are likely still happening (small enough not to greatly affect overall
in on immigrant populations, he says, and on communities where socio-economic
constraints lead to malnutrition and health-care problems, and generations of
new children continue to grow taller since height maximums have not yet been reached.
is large heterogeneity in ethic compositions," he says. "When you look
at Asian-Americans, Hispanic Americans — those are the pockets where increases
in height are still happening."
dating from the 1930s have demonstrated how a person's environment — and
in turn nutrition — can directly affect not only a person's size, but also
analyses done on European immigrants to the United States and their children 60
years ago, researchers showed immigrant children born in the United States were
taller and had larger heads and broader facial features than their foreign-born
parents and siblings who were born abroad.
recent studies, done in the 1960s and 1970s have indicated the importance of nutrition
to height even more directly. Over this time period anthropologists analyzed a
series of villages in Central America. To infants in some villages, they provided
nutritional supplements, while in
others they supplied only placebos.
the children who had received the supplements
in youth grew taller and were even more successful throughout life.
Seasons of Life
a person receives good nutrition is critical since growth occurs almost exclusively
in infancy and adolescence. Humans grow fastest during the first two to three
years of life, then growing slows through childhood until about age 10 or 11.
this point, says Leonard, girls accelerate in height to reach their maximum by
age 17 while boys shoot up a little later, reaching their tallest by age 20. One
of America's most famous tall people, Wilt Chamberlain, hit a major growth spurt
at age 15, when he grew four inches in three months. By the time he started playing
college basketball he had reached a towering 7 feet 1 inch.
beyond the age of 20, says Leonard, is rare. But interestingly, late growth spurts
are more likely to occur when poor nutrition has inhibited growth earlier in life.
In the malnourished
communities in South America, for example, people continued growing throughout
their 20s. But these people still remained shorter than most Americans, since
they grew less during the more critical years of childhood.
tallness reflects a person's early health and nutrition, tallness, in turn, can
be a good indicator of a person's longevity. A recent study by David Gunnell,
an epidemiologist at England's University of Bristol, showed that at least in
older times, good height meant a long life.
Linked to Longevity
measured hundreds of human arm and leg bones exhumed from English graves from
between the ninth and 19th centuries. His studies showed that the longer the bone
length (bone length correlates to overall height), the more likely a person lived
beyond the age of 30.
modern times being tall can help a person be more successful — sexually and
professionally. In the United States studies have shown taller presidential candidates
are more likely to be elected (with the notable recent exception of George W.
Bush) and anecdotal evidence suggests that taller people appear more attractive
and so have an easier time finding sexual partners.
Height Is a Hindrance
Wolf Blanckenhorn of the University of Zurich, Switzerland, points out that animal
evidence show that being too tall can have drawbacks.
animals need to eat more and so can have a harder time surviving when food is
scarce. Taller animals also tend to be less agile and so are more vulnerable to
predators and parasites.
people, being very tall can add strain to the circulatory and skeletal systems.
And anecdotal evidence points to other difficulties.
of all the little disadvantages tall basketball players have in everyday life
with food, clothing, living quarters, beds, etc.," Blanckenhorn points out.
these reasons, anthropologists think it's unlikely that Americans will develop
a new genetic pool to become even taller, now that they appear to have reached
their genetic growth potentials.
means that very tall Americans are likely to continue to be perceived as, well,
being very tall. And, as Leonard points out, being different in any way —
even in height — isn't always easy.
may have won fame and adoration for his height and skill on the court, but he
had to have special fixtures put in his house to accommodate his size, and was
known to say:
roots for Goliath."~*
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