Organisms are named using their genus and species, a binomial system of classification. Organisms today are grouped into five kingdoms. Humans evolved from primates, most of which live in trees. Primates have an opposable thumb, a shortened snout, stereoscopic vision, extended parental care of offspring, and an emphasis on learned behavior during a lengthy juvenile dependency period. Humans are most closely related to the apes.
Chimpanzees are our closest relatives.
Humans can be distinguished from apes by posture, locomotion, dental features, and various other traits. Several species of hominids may have existed 2 MYA, descending from Lucy's species. Stone flakes were used to clean hides and remove meat from bones. Speech was likely in this group, which also probably possessed attributes of culture and cooperation. Brain size, posture, and dentition cause H. habilis to be classified as a Homo.