The New Human movement represented a popular advancement of the Human civilization in the 23rd century, a grouping created as an outgrowth of the advantage of potential in Humankind on Earth and other Federation worlds where Human populations lived in total peace and were able to devote themselves entirely to their own betterment. Without conflict and turmoil, education became more advanced and the intelligence of the average individual increased, creating a dynamic of social freedom not before experienced by the species.
Many also pursued the advancement of the telepathic and extrasensory potential of the Human species, which had previously never been utilized to any significant degree. Group minds formed as the new Humans found they could create long lasting telepathic bonds in groups that individuals could not realistically sustain.
New Humans were more intelligent than normal Humans that did not have the same advantages, but they also proved to be incapable of deep space exploration because they weren't able to cope with authority structures and the inevitable encounters with advanced alien lifeforms, especially those with advanced intellects or those who came into conflict with the views of the new Human culture.
By the 2270s, New Humans made up a sizable percentage of Earth's population and were increasingly critical of Starfleet's cost, aims, and core values. Because of this, Admiral Heihachiro Nogura, a seasoned veteran, was made commanding admiral as his career was, in the media, very much a symbol of the purity of Starfleet's values. Nogura's renown among civilians and officers alike helped to quash the critics. (TOS novelization: The Motion Picture; TOS novel: Triangle)