Human height

Overview
Human height varies according to both "nature" and "nurture". The particular human genome that an individual inherits is a large part of the first variable (nature), and a combination of health and environmental factors present before adulthood (when growth stops) are a major part of the second determinant ("nurture"). Hereditary factors include both genes and chromosomes, and are inborn. Environmental factors are events that occur before adult height is reached, such as diet, exercise, and living conditions.

When populations share genetic background and environmental factors, average height is frequently characteristic within the group. Exceptional height variation (around 20% deviation from average) within such a population is usually due to gigantism or dwarfism; which are medical conditions due to specific genes or to endocrine abnormalities. In regions of extreme poverty or prolonged warfare, environmental factors like malnutrition during childhood and/or adolescence may account for marked reductions in adult stature even without the presence of any of these medical conditions. This is one reason that immigrant populations from regions of extreme poverty to regions of plenty may show an increase in stature, despite sharing the same gene pool.

The average height for each sex within a population is significantly different, with adult males being (on average) taller than adult females. This difference may be attributed to sex chromosomal differences, XY (male) as opposed to XX (female). Women ordinarily reach their greatest height at a younger age than men. Vertical growth stops when the long bones stop lengthening, which occurs with the closure of epiphyseal plates. These plates are bone growth centers that disappear ("close") under the hormonal surges brought about by the completion of puberty. Puberty generally occurs several years earlier in young women than in young men, and so final adult height is reached earlier in women. Adult height for one sex in a particular ethnic group follows more or less a normal distribution.

Adult height between ethnic groups often differs significantly, as presented in detail in the chart below. For example, the average height of women from the Czech Republic is currently greater than that of men from Malawi. This may be due to genetic differences, to childhood lifestyle differences (nutrition, sleep patterns, physical labor) or to both.

At 2.57 metres (8 ft 5.5 in), Leonid Stadnyk is the world's tallest living man and is from Ukraine. The tallest man in modern history was Robert Pershing Wadlow from Alton, Illinois, who was born in 1918 and stood 8 ft 11.1 inches (2.72 m) at the time of his death in 1940.

The maximal height that an individual attains in adulthood is not maintained throughout life if that life is a very long one. Again, depending on chromosomal (male v. female), genetic, and environmental factors, there is shrinkage of stature that may begin in middle age in some individuals but is universal in the extremely aged. This decrease in height is due to such factors as decreased height of inter-vertebral discs because of dessication, atrophy of soft tissues, and postural changes secondary to degenerative disease.

Average adult height around the world
Below are average adult heights by country. (The original studies and sources should be consulted for details on methodology and the exact populations measured, surveyed, or considered.)

Determinants of growth and height
The study of human growth is known as auxology. Growth and height have long been recognized as a measure of the health and wellness of individuals, hence part of the reasoning for the use of growth charts. For individuals, as indicators of health problems, growth trends are tracked for significant deviations and growth is also monitored for significant deficiency from genetic expectations. Genetics is a major factor in determining the height of individuals, though it is far less influential in regard to populations. Average height is increasingly used as a measure of the health and wellness (standard of living and quality of life) of populations. Attributed as a significant reason for the trend of increasing height in parts of Europe is the egalitarian populations where proper medical care and adequate nutrition are relatively equally distributed. Changes in diet (nutrition) and a general rise in quality of health care and standard of living are the cited factors in the Asian populations. Average height in the United States has remained essentially stagnant since the 1950s even as the racial and ethnic background of residents has shifted. Severe malnutrition is known to cause stunted growth in North Korean, portions of African, certain historical European, and other populations. Diet (in addition to needed nutrients; such things as junk food and attendant health problems such as obesity), exercise, fitness, pollution exposure, sleep patterns, climate (see Allen's rule and Bergmann's Rule for example), and even happiness (psychological well-being) are other factors that can affect growth and final height.

Height is, like other phenotypic traits, determined by a combination of genetics and environmental factors. Genetic potential plus nutrition minus stressors is a basic formula. Genetically speaking, the heights of mother and son and of father and daughter correlate, suggesting that a short mother will more likely bear a shorter son, and tall fathers will have tall daughters. Humans grow fastest (other than in the womb) as infants and toddlers (birth to roughly age 2) and then during the pubertal growth spurt. A slower steady growth velocity occurs throughout childhood between these periods; and some slow, steady, declining growth after the pubertal growth spurt levels off is common. These are also critical periods where stressors such as malnutrition (or even severe child neglect) have the greatest effect. Conversely, if conditions are optimal then growth potential is maximized; and also there is catch-up growth — which can be significant — for those experiencing poor conditions when those conditions improve.

Moreover, the health of a mother throughout her life, especially during her critical periods, and of course during pregnancy, has a role. A healthier child and adult develops a body that is better able to provide optimal prenatal conditions. The pregnant mother's health is important as gestation is itself a critical period for an embryo/fetus, though some problems affecting height during this period are resolved by catch-up growth assuming childhood conditions are good. Thus, there is an accumulative generation effect such that nutrition and health over generations influences the height of descendants to varying degrees.

The age of the mother also has some influence on the her child's height. Although 2 Esdras recorded that "Those born in the strength of youth" were taller than "those born during the time of old age, when the womb is failing", studies in modern times have observed a gradual increase in height with maternal age.

The precise relationship between genetics and environment is complex and uncertain. Human height is 90% heritable and has been considered polygenic since the Mendelian-biometrician debate a hundred years ago. The only gene so far attributed with normal height variation is HMGA2. This is only one of many, as each copy of the allele concerned confers an additional 0.4 cm, accounting for just 0.3% of population variance.

Race and height
The Nilotic peoples of Sudan such as the Dinka have been described as the tallest in the world, with the males in some communities having average heights of 1.9 m (6 ft 3 in) and females at 1.8 m (5 ft 11 in). A notable example is Manute Bol, who, at 2.31m(7ft 7in), was the tallest basketball player in the NBA. The Dinka are characterized as having long legs, narrow bodies and short trunks, an adaptation to hot weather. However, a 1995 study casts doubt on the claim of extraordinary height in Dinka, which after studying the average height of Dinka males in one location, listed the actual number as 1.76 m (5 ft 9.45 in.) Adults of the Pygmy peoples have an approximate average height of 1.5 m (4 ft 11 in).

Process of growth
Growth in stature, determined by its various factors, results from the lengthening of bones via cellular divisions chiefly regulated by somatotropin (human growth hormone (hGH)) secreted by the anterior pituitary gland. Somatotropin also stimulates the release of another growth inducing hormone insulin-like growth factor 1 (IGF-1) mainly by the liver. Both hormones operate on most tissues of the body, have many other functions, and continue to be secreted throughout life; with peak levels coinciding with peak growth velocity, and gradually subsiding with age after adolescence. The bulk of secretion occurs in bursts (especially for adolescents) with the largest during sleep. Exercise promotes secretion. Adolescents who take steroids can experience stunted growth. A positive net nutrition is also important, with proteins and various other nutrients especially important.

The majority of linear growth occurs as growth of cartilage at the epiphysis (ends) of the long bones which gradually ossify to form hard bone. The legs compose approximately half of adult human height, and leg length is a somewhat sexually dimorphic trait. Height is also attained from growth of the spine, and contrary to popular belief, men are the "leggier" sex with a longer leg to torso ratio, conversely to women's longer torso to leg ratio. (The illusion of the proportion being the other way around is caused by fatty deposits placed high on women's hips.) Some of this growth occurs after the growth spurt of the long bones has ceased or slowed. The majority of growth during growth spurts is of the long bones. Additionally, the variation in height between populations and across time is largely due to changes in leg length. The remainder of height consists of the cranium. Height is sexually dimorphic and statistically it is more or less normally distributed, but with heavy tails.

Height abnormalities
Most intra-population variance of height is genetic. Short stature and tall stature are usually not a health concern. If the degree of deviation from normal is significant, hereditary short stature is known as familial short stature and tall stature is known as familial tall stature. Confirmation that exceptional height is normal for a respective person can be ascertained from comparing stature of family members and analyzing growth trends for abrupt changes, among others. There are, however, various diseases and disorders that cause growth abnormalities. Most notably, extreme height may be pathological, such as gigantism (very rare) resulting from childhood hyperpituitarism, and dwarfism which has various causes. Rarely, no cause can be found for extreme height; very short persons may be termed as having idiopathic short stature. The Food and Drug Administration (FDA) in 2003 approved hGH treatment for those 2.25 standard deviations below the population mean (approximately the lowest 1.2% of the population). An even rarer occurrence, or at least less used term and recognized "problem", is idiopathic tall stature.

If not enough growth hormone is produced and/or secreted by the pituitary gland, then a patient with growth hormone deficiency can undergo treatment. This treatment involves the injection of pure growth hormone into thick tissue to jump-start the growth process.

Role of an individual's height
Tallness has been suggested to be associated with better cardio-vascular health and overall better-than-average health and longevity (Njolstad et al. 1996, McCarron et al 2002 ). However, height may not be causative of better health and longevity (Miura et al. 2002). Other studies have found no association, or suggest that shorter stature is associated with better health (Samaras & Elrick, 1999 ). On the other hand, being excessively tall can cause various medical problems, including cardiovascular issues, due to the increased load on the heart to supply the body with blood, and issues resulting from the increased time it takes the brain to communicate with the extremities. For example, Robert Wadlow, the tallest man known to verifiable history, developed walking difficulties as his height continued to increase throughout his life. In many of the pictures of the later portion of his life, Wadlow can be seen gripping something for support. Late in his life he was forced to wear braces on his legs and to walk with a cane, and he died after developing an infection in his legs because he was unable to feel the irritation and cutting caused by his leg braces (it is important to note that he died in 1940, before the widespread use of modern antibiotics). Height extremes of either excessive tallness or shortness can cause social exclusion and discrimination for both men and women (heightism).

Epidemiological studies have also demonstrated a positive correlation between height and intelligence. The reasons for this association appear to include that height serves as a biomarker of nutritional status or general mental and physical health during development, that common genetic factors may influence both height and intelligence, and that both height and intelligence are affected by adverse early environmental exposures.

In addition, an individual's height can be largely a part of what social clique, or group that they fall in to, though this is usually associated with pre-teens and teenagers. For example, in some schools, students on the basketball team might be "cool," and those with short stature wouldn't likely make the team. Therefore, in some cases, this could contribute to them being classified as "uncool," which can be detrimental to that particular individual's self-esteem. A study done on men in Sweden has shown that there is a strong correlation between subnormal stature and suicide.

This can also sometimes be translated over into the corporate world. Individuals with short stature can sometimes appear to not have any leadership ability or power, since some people might not take them seriously due to their short stature. However, this is not always the case with most employers. Historically this assumption has not always reflected reality; for instance Napoleon was not much taller than 5ft according to sources (though Napoleon's height is subject to great debate, and he may have been as tall as 5' 7", see Napoleon's height for further information). Ignatius Loyola, founder of the Jesuit order was 5'. Both Lenin and Stalin were of below average height. A modern example would be Deng Xiaoping of China who undertook massive reforms to the Chinese economy in the 1980s and was reported to have only been 5' 2".

The role of height in sports
Height often plays a crucial role in sports. For most sports, height is useful as it affects the leverage between muscle volume and bones towards greater speed of movement. It is most valuable in sports like basketball and volleyball, where the "short" players are almost always well above average in height compared to the general population. In men's professional basketball, the guards, the smallest players, are usually around 6'2" to 6'6" (1.88 to 1.98 m), and the centers, the tallest players, are generally from 6'10" to 7'2" (2.08 to 2.18 m). Famous basketball player Shaquille O'Neal is listed at 7'1" (2.16 m). In some sports, such as horse racing, auto racing, figure skating, diving, and gymnastics, a smaller frame is more valuable. In other sports, the role of height is specific to particular positions (i.e . In American Football, running backs have an advantage if they are shorter than the defenders due to lower centers of gravity and decreased visibility.) In Rugby Union Height is Vital for key positions such as Second Row who catch the ball while being hoisted up in lineouts. In weightlifting shorter levers are advantageous and taller than average competitors usually compete in the 105 kg + group.

Association football (Soccer)
For example, in Association football, tall goalkeepers have an advantage because they have greater armspans and can jump higher easily, so one will rarely, if ever, see a short goalkeeper at the professional level. However, shorter goalkeepers will have an easier time reaching low shots as they can reach the ground fractionally sooner than taller keepers. In wide positions and certain attacking ones, height is not always important with some of the best players in the world (e.g. Garrincha, Edgar Davids, Romário and Maradona) being shorter than average and in many cases gaining an advantage with their low center of gravity. However, height is generally considered advantageous for central defenders and for target men forwards who usually aim to score with their head for instance Jan Koller, Ruud van Nistelrooy, Niall Quinn and Peter Crouch.

Cricket
Similarly, in cricket, some great batsmen like Donald Bradman 5 ft, Sachin Tendulkar 5 ft, Brian Lara 5 ft, Sunil Gavaskar 5 ft and Aravinda De Silva 5 ft are/were short. On the other hand, many successful fast bowlers are/were well over 6 ft; for example past greats Joel Garner, Courtney Walsh, and Curtly Ambrose were all 6'6"(198 cm) or taller. Glenn McGrath is also 6'5½" (197 cm). In general, taller bowlers have a higher point of release in their bowling action, making it easier for them to make the ball rear-up from a length. Also, they can generate more pace with longer arms and the sling action associated with bowling. But, taller batsmen also have greater ease of hitting the ball compared to short-heighted. Some greats like Clive Lloyd are above 6 ft. England's star batsman Kevin Pietersen is 6 ft tall, while New Zealand all-rounder Jacob Oram measures 6 ft.

Rowing
In rowing, being tall is a big advantage, because the taller you are the longer your stroke can potentially be, thus moving the boat more effectively. The average male Olympic rower is 6'3.5", and the average female Olympic rower is 5'8", well over the average height.

Rugby Union
In rugby union, lineout jumpers, generally s, are usually the tallest players on the pitch, as this increases their chance of winning clean ball, whereas are usually relatively short. As examples, current world-class locks Victor Matfield, Chris Jack, and Paul O'Connell are all at least 6'6"/1.98 m, and Simon Shaw even gets up to roughly 6'9", while the sport's all-time leader in international appearances, scrum-half George Gregan, is 5'8"/1.73m. Currently the tallest professional players are Devin Toner and Andries Bekker, who are both 6'10". The tallest man ever to have played was 7'0" tall Richard Metcalfe.

Rugby League
Unlike rugby union, height was not seen as important in Rugby League, due to the absence of line-outs. However, recent tactics of cross-field kicking has resulted in the success of taller outside backs. Israel Folau (194cm) and Krisnan Inu (185cm) are examples of the trend in taller wingers and centres, and are both known for their remarkable jumping skills in defense or attack.

American Football (Gridiron)
In American Football, a tall quarterback is at an advantage because it is easier for him to see over the heads of large offensive and defensive linemen while he is in the pocket in a passing situation. At 5'9", Doug Flutie was initially considered to be too short to become a NFL quarterback despite his Heisman Trophy-winning success at the college level.

Tall wide receivers have an advantage of being able to outjump shorter defensive backs to catch highly thrown passes. By contrast, shorter defensive backs are utilized because of their typically greater agility, as the ability to change directions instantly is a prerequisite for the position. Short running backs are at an advantage because their shorter stature and lower center of gravity generally makes them harder to tackle effectively. In addition, they can easily "hide" behind large offensive linemen, making it harder for defenders to react at the beginning of a play. Thus, in the NFL and in NCAA Division I football, running backs under 6 ft 0 in (1.83 m) are more common than running backs over 6 ft 3 in (1.91 m). Former Heisman Trophy winner and Pro Football Hall of Famer Barry Sanders, thought by some to be the greatest running back in history, is a classic example of a running back with an extraordinarily low center of gravity, as he stood only 5 ft 7 1/2 in (1.71 m). However, Jim Brown, another player often considered the greatest running back of all time, was more than 6 ft 2 in (1.88 m) tall, demonstrating benefits conferred by the greater power and leverage which height provides.

Kickers are generally short, they are shorter because this allows them to get under the ball easier. Punters are generally very tall because of longer legs achieving greater leg swing and this translates into more power on the ball.

Baseball
In baseball, pitchers tend to be taller than position players. Being taller means longer legs, which power pitches use to generate velocity and a release point closer to the plate, which means the ball reaches the batter more quickly. While taller position players have a larger strike zone, most position players are at least of average height because the larger frame allows them to generate more power. Most successful modern pitchers are safely over 6 feet/1.83 m, some to extremes (e.g., the 6'10"/2.08 m Randy Johnson), with the 5'11"/1.80 m Pedro Martínez a notable exception.

Ice Hockey
While the history of the NHL is filled with diminutive players who achieved greatness (Theo Fleury, Martin St. Louis,) the game's physical style has put a premium on imposing players, particular over 6 feet tall and over 200 pounds (Mario Lemieux, Chris Pronger). Taller, bigger players have a longer reach, are able to give out and sustain punishing body checks, and are generally seen as indispensable for a team looking to go deep into the playoffs. Zdeno Chára, at 6 ft 9 in (2.06 m), is the tallest player ever to play in the NHL.

Wrestling
Height can be both helpful and detrimental in wrestling. Since taller people have more bone mass, they will generally be slightly weaker than shorter people in the same weight class. This difference is made up in part by their longer arms, which allow them a longer reach and make cradles easier. Also, taller peoples' legs are longer and harder to defend from shorter wrestlers.

Sumo
Professional sumo wrestlers are required to be at least 173 cm tall. Some aspiring sumo athletes have silicon implants added to the tops of their heads to reach the necessary height. The average height for a sumo wrestler is 180 cm, far above the national average in Japan.

History of human height
Average Height of Troops Born in the Mid-Nineteenth Century, by Country or Place

Source
 * Tallest in the World: Native Americans of the Great Plains in the Nineteenth Century
 * European Heights in the Early 18th Century

In the 18th and 19th centuries, Europeans in North America were far taller than those in Europe and were the tallest in the world. The original indigenous population of Plains Native Americans was also among the tallest populations of the world at the time. Several nations, including many nations in Europe, have now surpassed the US, particularly the Netherlands, and the Scandinavian nations.

In the late nineteenth century, the Netherlands was a land renowned for its short population, but today it has the 2nd tallest average in the world, with young men averaging 185 cm (6'1 ft) tall and only shorter than the peoples of the Dinaric Alps (a section largely within the former Yugoslavia which encompasses: all of present-day Montenegro, a sovereign republic; Herzegovina, its entire region within another republic; hinterland and coastal Croatia, Serbia), where males average 185.6 cm (6 ft 1.1 in) tall. The Dinarians and Dutch are now well known in Europe for extreme tallness. In Africa, the Maasai, Dinka and Tutsi populations are known for their tallness.

Average male height in impoverished Vietnam and North Korea remains comparatively small at 163 cm (5 ft 4 in) and 165 cm (5 ft 5 in), respectively. Currently, young adult North Korean males are actually significantly shorter. This contrasts greatly with the extreme growth occurring in surrounding Asian populations with correlated increasing standards of living. Young South Koreans are about 12 cm (5.5 inches) taller than their North Korean counterparts, on average. There is also an extreme difference between older North Koreans and young North Koreans who grew up during the famines of the 1990s-2000s. North Korean and South Korean adults older than 40, who were raised when the North and South's economies were about equal, are generally of the same average height.

In the early 1970s, when anthropologist Barry Bogin first visited Guatemala, he observed that Mayan Indian men averaged only 157.5 cm (5 ft 2 in) in height and the women averaged 142.2 cm (4 ft 8 in). Bogin took another series of measurements after the Guatemalan Civil War had erupted, during which up to a million Guatemalans had fled to the United States. He discovered that Mayan refugees, who ranged from six to twelve years old, were significantly taller than their Guatemalan counterparts. By 2000, the American Maya were 10.24 cm (4 in) taller than the Guatemalan Maya of the same age, largely due to better nutrition and access to health care. Bogin also noted that American Maya children had a significantly lower sitting height ratio, (i.e. relatively longer legs, averaging 7.02 cm longer) than the Guatemalan Maya.