The term "human beings" refers to members of the species Homo sapiens, a bipedal African ape distinguished by its lack of hair, large brain and elaborate social structures. Humans have been independently evolving for between 6 and 8 million years since the split with their closest living relatives, the two extant species of chimpanzee.
Humans are sexually dimorphic, split between male and female in a stable division, and may be loosely grouped into unstable haplotypes, or races, with shifting borders and little effect on individuals' anatomy or physiology. While there exists some variation among individuals, humans generally lack the thick coat of fur observed among other mammals. Entirely unique among vertebrates, most humans wear some kind of clothing made from either fabric or animal skin.
With only minor individual variations, humans generally use tools to alter the surrounding world. Human beings are distinguished by the ability to consume energy outside the body, and to use this energy to do work. Like other primates, members of H. sapiens form communities. Unlike other primates, however, human communities range across a broad spectrum from small family groups of a few dozen individuals to vast nation states with over 1 billion citizens.
Human beings are also intellectually unique. Fully functional adult members of the species are capable of highly abstract thought and generalization. As a result, most are aware of their mortality to a degree unknown among animals, and many are capable of a high degree of empathy for other living things.