From the recently discovered bones of the so-called "hobbits", meter-tall hominids who lived 18,000 years ago, to the towering supermodels and basketball players of our In the modern world l human height has varied immensely (Culotta 983). Scientists have postulated many explanations for this height heterogeneity, but none of these explanations have provided a complete picture of this complex trait. Instead, evolutionary, physiological, genetic, and environmental explanations were needed to understand why individuals and groups differ in size. Today, the shortest people on Earth are the Efe Pygmies of the Congo Basin in Central Africa (Diamond). By studying the myriad reasons why Efes are so small, we can begin to see the challenge scientists face in trying to predict height based solely on genetics. Unlike most other pubescent humans, Efe adolescents do not have an adolescent growth spurt. In fact, their growth stops around age thirteen, just when most other young people have recently begun to mature rapidly (Swaminathan 1). The endocrine system plays a vital role in the accelerated growth experienced by most human adolescents, secreting insulin-like growth factors I and II along with other hormones that stimulate growth and adapt growth to environmental factors (Bogin 330). Blood tests of Efe adolescents show that they have less than a third of the insulin-like growth factor I that an average non-Efe adolescent would have (Diamond). Scientists have determined that “the insulin-like growth factor defect in pygmies…is genetically based and unrelated to environmental factors” (“African Pygmies” 177). It would be very tempting to assume that these studies show that …… half of the paper…… “A question of size”. Discover. np May 1, 1992. Web. March 5, 2010. Pierce, Benjamin A. Genetics: A Conceptual Approach. 2nd ed. New York: W. H. Freeman, 2006. Print.Shay, Ted. “Standards of Living in Japan, 1885-1938: New Evidence.” Height, standard of living and economic development: essays in anthropomorphic history. Ed. Giovanni Komlos. Chicago: University of Chicago Press, 1994. 173-96. Print.Swaminathan, Nikhil. “Not so tall story: why pygmies evolved to be shorter.” American scientist. Nature America Inc., December 12, 2007. Web. March 5, 2010. Walker, Robert S., and Marcus J. Hamilton. "Life history consequences of density dependence and the evolution of human body size." Current Anthropology, February 2008: 115-22. Press.