This gives insights into the biological mechanisms underlying how these 697 genetic variants affect overall height. These loci do not only determine height, but other features or characteristics. As an example, 4 of the 7 loci identified for intracranial volume had previously been discovered for human height.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 157.5 centimetres (5 ft 2 in) in height and the women averaged 142.2 centimetres (4 ft 8 in). 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 10.24 cm (4.03 in) 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 7.02 cm (2.76 in) longer than the Guatemalan Maya (a significantly lower sitting height ratio).The Nilotic peoples of Sudan such as the Shilluk and Dinka have been described as some of the tallest in the world. Dinka Ruweng males investigated by Roberts in 1953–54 were on average 181.3 centimetres (5 ft 11+1⁄2 in) tall, and Shilluk males averaged 182.6 centimetres (6 ft 0 in).
Urban mortality was also much higher than in rural regions. In 1829, the average urban and rural Dutchman was 164 cm (5 ft 4+1⁄2 in). By 1856, the average rural Dutchman was 162 cm (5 ft 4 in) and urban Dutchman was 158.5 cm (5 ft 2+1⁄2 in).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 12 cm (4.7 in) 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 13 centimetres (5 in) shorter than South Koreans their age due to malnutrition.The tallest living man is Sultan Kösen of Turkey, at 251 cm (8 ft 3 in).