Por que existem humanos mais altos e outros mais baixos?

Why are some humans taller and others shorter? The average Dutchman is more than 30 centimeters taller than some groups in the rainforest. They are members of the same species, with the same biology. What determined where each human group ended up on this spectrum? The answer combines more than 700 genes, animal protein, parasites, climate, and an evolutionary logic that changes how you see your own body. • Why height is controlled by over 700 genetic variants, not a single gene • How animal protein in childhood directly activates growth hormone via leucine and mTOR • Why generations of Japanese and Koreans raised in the US have become significantly taller • Bergmann's Rule: why cold climates favor larger bodies and warm climates smaller bodies • The evolutionary logic of short stature: how growing less was advantageous in high-density forests • Why pastoral populations like the Maasai tend to be taller than neighboring farmers • The IGF1 gene and its highly prevalent low-expression variants in small populations • How intestinal parasite load limits nutrient absorption and compromises growth • Why the caloric cost of height was a real disadvantage in scarcity environments • The global increase in height in the 20th century: evidence that nutrition trumps genetics in growth Sources: Timothy Spector, King's College London — research on the genetics of height and twin studies; Joel Hirschhorn and team, Broad Institute — genome-wide association studies identifying more than 700 variants associated with stature, published in Nature Genetics; Barry Bogin, Loughborough University — longitudinal research on the growth of Guatemalan and Mayan migrant populations in the USA; Andrea Wiley, Indiana University — research on dairy consumption and stature in historical populations; Evelyne Heyer, Musée de l'Homme — genetic analysis of tropical forest populations and selection for short stature.