A posthuman is a being whose basic capacities so radically exceed those of present humans as to be no longer unambiguously human by our current standards.

The first half-dozen posthumans who made their presence widely known to the public appeared during World War 2, as part of the Red Army fighting the invading forces of Nazi Germany. Soon after, similar groups of posthumans appeared, fighting for the Axis in Europe and Africa and for the Allies in Europe and the Pacific.

Today, scientists and journalists estimate that there are approximately 8,000 posthumans worldwide, roughly 500 of which are in the United States. Despite their incredible powers, posthumans have had a limited impact on world affairs. Posthuman geniuses have made extraordinary scientific and medical discoveries, but these advances have been kept from the public until the powerful have deemed society "ready". The primary beneficiaries of these scientific breakthroughs have been the governments and corporations who rule the world, and the powerful people who secretly control them.

Similarly, at the behest of conventional authorities, posthumans have generally refrained from involvement in everyday politics and diplomacy. The exceptions to this rule have been condemned as terrorists and threats to all of humanity. This phenomenon was most evident during the 1950s, when a small group of politically active posthumans calling themselves the Committee For The Advancement Of Mankind were convicted in absentia of violating the Smith Act.

Most posthumans have the same thoughts, feelings, and behaviors as their human counterparts. These behaviors are the result not only of their individual experiences and environment, but also of what happened to their ancestors millions of years ago. As such, human nature is shared, to a large extent, by everyone on Earth, even posthumans. Like most human beings in the Kalos Universe, posthumans are often selfish and seek to improve their own condition. At the same time, human beings have a great capacity to cooperate, and they display enormous depths of compassion, even toward people they have never met; so do many posthumans.