Very short:

Very short stature occurs in a variety of populations native to different tropical rainforests worldwide. They are also called "Pygmies", the defining criterion for the term being an average height below 150 cm in adult males. By natural selection, groups that have long lived in dense tropical forests tend to become very short. Short stature can be beneficial if there is very dense vegetation, and if the air is hot and humid so that sweating is inefficient, as small stature limits heat during exertion. The shortest population mean ever found in a study is that of the Aiome of New Guinea, where adult men average 138 cm. Only marginally taller are the Mbuti Pygmies of Central Africa. In New Guinea, pygmy stature is common among several mountain tribes like Afere, Tapiro, Nogullo, Kamaweka. It also occurs in the Aeta of the Philippines and Andamanese Negritos. Sometimes in African Mbenga Pygmies and Kuna Indians of Panama.