To say that human beings as a species are characterized by neoteny is to note that, physically, we do not specialize very much as we mature. We retain, for the most part, the round faces and unspecialized features of our juvenile phase. In other words, our species is remarkably un-committed, biologically, to any specialized life-stye. We remain, in terms of our anatomy, "generalists" even into adulthood. In other words, neoteny is related to the remarkable adaptability of human beings, who remain even as adults able to adapt themselves to a wide array of life-situations, rather than fitting perfectly into a single niche. Because of this characteristic, this behavioral plasticity, humans have fitted themselves to almost all the planet's environments, from the equator to near the poles, and from sea-level to elevations higher than 12,000 feet.