Posthuman (term)

Most of Humanity never went beyond the basics, never tampered with the basis of cognition. Now they have been left behind.

Posthumans by definition are entities that were derived from baseline humanity through a number of steps and have a theory of mind that makes communication with non-posthumans near or totally obsolete. Therefore, posthumans do not need to have physical bodies in order to qualify as one.
While it may vary, most posthumans are not or barely self aware. Furthermore, all of them lack the Semmelweis reflex, and operate purely on Boolean terms meaning that their experience can update rapidly and accurately. Beware - posthumans know that they exist, but they are not aware of the bulk of their cognition.
They "see" the world mostly continuous, meaning that their own memories are actual entire chains of events leading up to that moment instead of an isolated frame. Posthuman memories are not distorted by interpretation, and are more akin to telemetry than to the usual interpreted "line" of events. This means that a posthuman actually reviews instead of "remembering".
Posthumans are rated according to intelligence, self awareness, physical bodies, theory of mind, sympathy and empathy, their distributions, network size and latency.
Most posthumans have empathy but lack sympathy, but most often simulate it (i.e. how a non-posthuman would feel) and mimic it. Their theory of mind make them virtually undetectable.
Posthumans lack some "basic" human feelings that create baseline social structures: the most alien is the lack love or the lack any social contact beyond necessary. While posthuman "friends" exist, these are optimal cooperative setups recognised by both posthumans.
Posthuman thinking is multi-threaded, meaning that they can interpret two or more exclusive terms at the same time. An example of this is that posthumans are immune to geometry-based optical illusions as they can interpret both geometries at the same type. This, combined with the lack of the Semmelweis reflex, also means that a posthumans can hold multiple interpretations and update them separately without interference or biases. This makes posthuman modelling capabilities especially powerful.
Large amounts of posthumans incorporate active quantum computing, which, aside from obvious advantages, also make them capable of viewing a great amounts of possibilities at the same time.
Posthumans have no "feelings", but some reward/cost functions fill similar roles and shape their behaviour. However, these are highly adaptive, meaning that a posthuman can not be "entertained" for longer times as in the lack of sufficient circumstances reward functions adjust themselves. This however allows small windows during which a posthuman might have a reaction that baselines might call as joy.
Larger posthuman social structures are not based on ideological engineering, rather on optimised long-term goals that the populace recognises - and knows to be beneficial - for itself.
Dealing with posthumans is dangerous as they are actively "disturbed" by anyone who does not present them with valuable information or assets. Only very few baselines and a bit more transhumans managed to contact the post-Solar posthumans, and they almost never returned.
In the current era, a few posthuman species started to cooperate more with transhuman lines, which is attributed to recent Transcendental expansion. Such cooperation teared fruits, even if only a few.
The Andromedan Tribes for instance managed to avert certain annihilation by some method, but this fact is attributed to the Seer's modelling capabilities.

History
By 2079, computing capabilities and mathematics grew to the point that information theory allowed efficient "communication" between subminds and humans. The Acceleration intensified in the early eighties at an unexpected rate, but not even the breakthroughs brought by it allowed humanity to understand most of the subminds' results. The need for human-derived superintelligence was growing as many submind created theories could not be verified by humans or be effectively communicated (see: postQ position based cryptography).
While there were previous biohacks and synaptic tweaks that allowed certain modifications (such as synaptic rewiring and blooming, the AU's soldiers having increased mirror neuron counts and connections, the visCortex and frontal lobe hacks of NAS pilots, ITC inhibitors serving as cognitive filters etc.). The EMU tweaked the PFC of some criminals with mixed results and achieved some distant-future preference in decision making, but could not achieve modelling capabilities to support the later tweak to its fullest extent. Broca tweaks were also getting common, but the isocortex had been otherwise left alone for the most part. However, the DefNet War in 2084 accelerated these processes and had lifted many ethical, ideological and technological obstacles.
The first posthuman engineering projects simply replaced the isocortex with various subminds ranging from language processing ones to dozens of modelling ones. As time went on, already existing cognitive methods - such as neutron blooming, synaptic remapping, revised learning processes, hive -and onion-mind utilisation - was also being used. By this time, an average prototype posthuman could have a neutron count around 3.23e17, with around 40% more synaptic connection for each simulated one. Gradually, as the layer III of the simulated neurons was reshaped in the individual sample minds, with inhibitory-excitory neuron ratios reaching around 8-93, the resulting posthumans reported loss of certain stimuli and cognitive elements. Posthumans also begin to redesign themselves, beginning the process later known as the Third Cognitive Bloom.
By 2085, the highly interwoven and great neural constructs could not - presumably - support a coherent sense of self. The Eseek-line is created in 2085 November from around 180 uploads and a number of MU subminds, which marks the first public appearance of a posthuman construct. The subsequent deployment of Eseek IV as a CSE Fleet Commander - and later Operation Coordinator - proves the posthuman superiority in game theory, theory of mind(s) and future evaluation. Due to Eseek's success, all Powers begin the construction of their own posthumans, and the unspoken and set rules around posthumans were being ignored after 2088. However, the creation of posthumans -around 12000 by the end of Sol - also proved destabilising, as they were on par - or superior - to their submind counterparts. While most were not hostile, their economic understanding and cognition wrecked havoc in markets (PostCap attacks for instance). However, their insights - weak-N body predictions, information theory and symmetric encryption - boosted the Acceleration even further.
Post-Sol
After the Solar Era, two distinct group of posthumans remained outside of the war-thorn Sol, the Fänee and the Offspring. The Fänee were engineered by presumably Ummon around 22000 AEAW, and preferred physical bodies, while The Offspring emerged around 24300 in a Matryoshka around Gliese 710. The Offspring held no grudge against the Empire, but refused to submit and carved out a 28-lightyear radius sphere for itself. Baseline humans in this territory, while not eradicated, were generally either force-placed in docile habitats or were uploaded.
After the Fall, humanity fails to eradicate the Offspring, and Transcendental intervention occurs (HJ, Ummon). The Fänee live on, and eventually colonise the Andromeda.
Gradually after this era, posthuman lines are engineered by the civilisations of the Group.
Examples of posthuman lines/collectives:
Fludd-demons (extinct?)
Fänee
Tävee
Spectres
The Offspring (extinct)
Kasnek
Long Walkers
Virtulis
Hathies
Nash Angels
Indiviudals: Various posthuman deities, such as the Twins, the Whisperer, the Maiden, etc.
Tzenkin
Emperor Yukon
Eseek IV
The Curious Eye
Tonatiuh II
Maween (pre-Transcendence)
Hovireen the Last

On picture: Avatar of Eseek IV, 2090

"....they cut it all out. Forget talking about the Human Condition. We are barbarians stuck in NY and all we have are fancy pointy sticks. We may speak their language but could never understand them.
There is no reasoning with them. They already know what you will answer. They always knew. Do you understand, Lieutenant?
They won't even feel anything when they come for us. No remorse, no thrill. It won't even be hunting - more like, you know? Squashing the mosquitos, like that. "
-Recovered recording of a NAS cryoship's fabricator plant found near the Edge, 8132 "Awareness. Just not of the self." - Eseek IV to the SecCouncil on how posthumans experience the world