question: Why are people now so much taller than they were hundreds of years ago?
comment: Generally speaking, it's access to better nutrition and healthcare. The human body needs to have a good supply of nutrients at certain key points in life (ex. puberty) to grow properly. Children in poverty-stricken areas without the same access exhibit stunted growth. As we can assume, people hundreds of years ago didn't have the same food choices we have today in the same way as the poor kids.
passages: Section::::History of human height.
  
  In the 150 years since the mid-nineteenth century, the average human height in industrialised countries has increased by up to . However, these increases appear to have largely levelled off. Before the mid-nineteenth century, there were cycles in height, with periods of increase and decrease; however, examinations of skeletons show no significant differences in height from the Stone Age through the early-1800s.
   Attributed as a significant reason for the trend of increasing height in parts of Europe are the egalitarian populations where proper medical care and adequate nutrition are relatively equally distributed. Average (male) height in a nation is correlated with protein quality. Nations that consume more protein in the form of meat, dairy, eggs, and fish tend to be taller, while those that attain more protein from cereals tend to be shorter. Therefore, populations with high cattle per capita and high consumption of dairy live longer and are taller. Historically, this can be seen in the cases of the United States, Argentina, New Zealand and Australia in the beginning of the 19th century. 
   Increases in human stature are a main indicator of improvements in the average health of populations. The newest data set for the average height of adult male birth cohorts, from the mid-nineteenth century to 1980, in 15 European countries was studied (in the populations listed).
  
  During a century average height increased by 11 cm representing a dramatic improvement of this phenomenon. The apparent acceleration of body height occurred during the Ĝ.
  
  In the mid-nineteenth century young European women's menarche occurred at the average age of 16.5 years. One hundred years later, this age was reduced to under 12 years.
   In general, there were no big differences in regional height levels throughout the nineteenth century. The only exceptions of this rather uniform height distribution were people in the Anglo-Saxon settlement regions who were taller than the average and people from Southeast Asia with below-average heights. However, at the end of the nineteenth century and in the middle of the first globalisation period, heights between rich and poor countries began to diverge. These differences did not disappear in the deglobalisation period of the two World wars. Baten and Blum (2014) find that in the nineteenth century, important determinants of height were the local availability of cattle, meat and milk as well as the local disease environment. In the late-twentieth century, however, technologies and trade became more important, decreasing the impact of local availability of agricultural products.
   Section::::External links.
  
  BULLET::::- CDC National Center for Health Statistics: Growth Charts of American Percentiles
  
  BULLET::::- fao.org, Body Weights and Heights by Countries (given in percentiles)
  
  BULLET::::- The Height Gap, Article discussing differences in height around the world
  
  BULLET::::- Tallest in the World: Native Americans of the Great Plains in the Nineteenth Century
  
  BULLET::::- European Heights in the Early eighteenth Century
  
  BULLET::::- Spatial Convergence in Height in East-Central Europe, 1890–1910
  
  BULLET::::- The Biological Standard of Living in Europe During the Last Two Millennia
  
  BULLET::::- HEALTH AND NUTRITION IN THE PREINDUSTRIAL ERA: INSIGHTS FROM A MILLENNIUM OF AVERAGE HEIGHTS IN NORTHERN EUROPE
   It is estimated that the worldwide average height for an adult human male is about , while the worldwide average height for adult human females is about . Shrinkage of stature may begin in middle age in some individuals, but tends to be typical in the extremely aged. Through history human populations have universally become taller, probably as a consequence of better nutrition, healthcare, and living conditions. The average mass of an adult human is for females and for males. Like many other conditions, body weight and body type is influenced by both genetic susceptibility and environment and varies greatly among individuals. (see obesity)
   Data derived from burials show that before 1850, the mean stature of males and females in Leiden, The Netherlands was respectively 166.7 cm (5 ft 5.6 in) and 156.7 cm (5 ft 1.7 in). The average height of 19-year-old Dutch orphans in 1865 was 160 cm (5 ft 3 in).
   Adult height between populations often differs significantly. For example, the average height of women from the Czech Republic is greater than that of men from Malawi. This may be caused by genetic differences, childhood lifestyle differences (nutrition, sleep patterns, physical labor), or both.
  
  Depending on sex, genetic and environmental factors, shrinkage of stature may begin in middle age in some individuals but tends to be universal in the extremely aged. This decrease in height is due to such factors as decreased height of inter-vertebral discs because of desiccation, atrophy of soft tissues and postural changes secondary to degenerative disease.
   "Nutrition was clearly part of the story of early mortality decline. ... With the beginnings of the agricultural revolution, the [Malthusian] trap began to fall apart. Per capita incomes began to grow and, perhaps for the first time in history, there was the possibility of steadily improving nutrition. Better nutrition enabled people to grow bigger and stronger, which further enabled productivity to increase. ... Taller, bigger people lived longer, and better nourished children were less likely to die and better able to ward of disease."
   The age of the mother also has some influence on her child's height. Studies in modern times have observed a gradual increase in height with maternal age, though these early studies suggest that trend is due to various socio-economic situations that select certain demographics as being more likely to have a first birth early in the mother's life. These same studies show that children born to a young mother are more likely to have below-average educational and behavioural development, again suggesting an ultimate cause of resources and family status rather than a purely biological explanation.
   It has been observed that first-born males are shorter than later-born males.
  
  However, more recently the reverse observation was made. The study authors suggest that the cause may be socio-economic in nature.
  
  Section::::Determinants of growth and height.:Nature versus nurture.
   A 2004 report citing a 2003 UNICEF study on the effects of malnutrition in North Korea, due to "successive famines," found young adult males to be significantly shorter. In contrast South Koreans "feasting on an increasingly Western-influenced diet," without famine, were growing taller. The height difference is minimal for Koreans over forty years old, who grew up at a time when economic conditions in the North were roughly comparable to those in the South, while height disparities are most acute for Koreans who grew up in the mid-1990s – a demographic in which South Koreans are about taller than their North Korean counterparts – as this was a period during which the North was affected by a harsh famine where hundreds of thousands, if not millions, died of hunger. A study by South Korean anthropologists of North Korean children who had defected to China found that eighteen-year-old males were 5 inches (13 cm) shorter than South Koreans their age due to malnutrition.
   Moreover, the health of a mother throughout her life, especially during her critical period and 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 for herself but also for the fetus 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 a cumulative generation effect such that nutrition and health over generations influences the height of descendants to varying degrees.
   Humans grow fastest (other than in the womb) as infants and toddlers, rapidly declining from a maximum at birth to roughly age 2, tapering to a slowly declining rate, and then during the pubertal growth spurt, a rapid rise to a second maximum (at around 11–12 years for female, and 13–14 years for male), followed by a steady decline to zero. On average, female growth speed trails off to zero at about 15 or 16 years, whereas the male curve continues for approximately 3 more years, going to zero at about 18–19. These are also critical periods where stressors such as malnutrition (or even severe child neglect) have the greatest effect.
   In support of the nutritional hypothesis, it is known that, in the United States, the average height before 1900 was about 10 cm (∼4 inches) shorter than it is today. Possibly related to the Flynn effect is a similar change of skull size and shape during the last 150 years. Though the idea that brain size is unrelated to race and intelligence was popularized in the 1980s, studies continue to show significant correlations.
   American-born colonial soldiers of the late-1770s were on average more than 7.6 cm (3 inches) taller than their English counterparts who served in the Royal Marines at the same time.
   Historians have used height to measure living standards during this time as average adult heights can point to a population's net nutrition - the amount of nutrition people grew up with as compared to biological stress which can cause lower heights in adulthood, stemming from things like food deprivation, hard work, and disease. According to military records of American and European men, Americans were on average two to three inches taller than Europeans.
   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. Malnutrition including chronic undernutrition and acute malnutrition is known to have caused stunted growth in various populations. This has been seen in North Korea, parts of Africa, certain historical Europe, and other populations. Developing countries such as Guatemala have rates of stunting in children under 5 living as high as 82.2% in Totonicapán, and 49.8% nationwide.
   In spite of concerns about overpopulation, widespread in developed countries, the number of people living in extreme poverty globally shows a stable decline (this has been disputed by some experts), even though the population has grown seven-fold over the last 200 years. Child mortality has declined, which in turn has led to reduced birth rates, thus slowing overall population growth. The global number of famine-related deaths have declined, and food supply per person has increased with population growth.
  
  Section::::History.:History of population growth.
   The effect of environment on height is illustrated by studies performed by anthropologist Barry Bogin and coworkers of Guatemala Mayan children living in the United States. In the early 1970s, when Bogin first visited Guatemala, he observed that Mayan Indian men averaged only in height and the women averaged . Bogin took another series of measurements after the Guatemalan Civil War, during which up to a million Guatemalans fled to the United States. He discovered that Maya refugees, who ranged from six to twelve years old, were significantly taller than their Guatemalan counterparts. By 2000, the American Maya were taller than the Guatemalan Maya of the same age, largely due to better nutrition and health care. Bogin also noted that American Maya children had relatively longer legs, averaging longer than the Guatemalan Maya (a significantly lower sitting height ratio).
   The average height of Americans and Europeans decreased during periods of rapid industrialisation, possibly due to rapid population growth and broad decreases in economic status. This has become known as the early-industrial growth puzzle or in the U.S. context the Antebellum Puzzle. In England during the early-nineteenth century, the difference between average height of English upper-class youth (students of Sandhurst Military Academy) and English working-class youth (Marine Society boys) reached 22 cm (8.7 in), the highest that has been observed.
   Height is a sexually dimorphic trait in humans. A study of 20th century British natality trends indicated that while tall men tended to reproduce more than short men, women of below average height had more children than taller women. 
  
  Section::::Determinants of growth and height.
   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, with men having proportionately longer legs. 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. 
   After the start of the Industrial Revolution, during the 18th century, the rate of population growth began to increase. By the end of the century, the world's population was estimated at just under 1 billion. At the turn of the 20th century, the world's population was roughly 1.6 billion. By 1940, this figure had increased to 2.3 billion. Each subsequent addition of a billion humans took less and less time: 33 years to reach three billion in 1960, 14 years for four billion in 1974, 13 years for five billion in 1987, and 12 years for six billion in 1999.
   Females are taller, on average, than males in early adolescence, but males, on average, surpass them in height in later adolescence and adulthood. In the United States, adult males are, on average, 9% taller and 16.5% heavier than adult females. There is no comparative evidence of differing levels of sexual selection having produced sexual size dimorphism between human populations.
  