They say the Highbrow clade started out as a joke. If that's true then it's a gag that's been running for almost 10,000 years.
Origin Legend as it that early in the First Federation a group of 'A list' personalities were attending a party and that the host of this party screened some pre-first century Sci-Fi vids he had scored while data mining. The bulk of the vids shown dealt with baseline humans confronting evolved humans or advanced aliens, both with huge heads to signify their superior intelligence. The vids were reportedly crude and childish but enjoyed by all, even the Su attending claimed to be amused. This might have been the end of the story if one of the partygoers had not been an unrepentant prankster. At the next party he showed up with a shaved head and a scalp full of sim-fat injections. The legend states the result was "riotous laughter" and when the next party occurred his stunt had been copied. This led to a game of 'one-upmanship' and sim-fat injections were soon replaced with skull reconstructions and wetwear implants. These people were becoming superbrights as a result of a joke.
Even in this early era intelligence augmentation was a mature science and there was no need for an "IA" to disfigure emself with a grossly enlarged head but these people had chanced upon an aesthetic that appealed to em. Others may have become superbrights before em but ey could now do it in a unique way. Ey quickly realized ey would need to guide eir development in much the same way the Superior clades had been. Ey also realized the game may have become secondary to the goal expanding eir intellect but eir competitive natures would not be easy to set aside. The legend further claims a small group of these proto-highbrows sat down one evening after dinner and used eir already augmented intelligence to carefully map out the future development of eir new clade. And the first thing ey would need was a genome for the future generations. It wasn't enough to simply use technology to continuously extend eir minds, ey wanted eir aesthetic to be inheritable. Ey wanted it to be passed down through the centuries and generations to come and after sixty-nine years of effort they had the genome ey needed.
Biology At first glance Highbrows appear to be baseline humans with the one distinguishing feature of having a head with a very large cranium. In truth eir whole bodies have been gengineered to support a mass of functional grey matter ten times larger than found in a modosophont hu of either nearbaseline or su lineage. Of course putting a brain weighing fourteen kilos into the skull would have caused many problems, not the least of which was the risk of injury to a seemingly baseline neck.
In a Highbrow the bones of the skull and vertebral column have been fused into a single unit with the additional feature that the bodies of the vertebrae form a hollow tube that widens as it descends into the torso. Because these bones are fused there is no movement in the back and neck, instead the bottom of the vertebral column has a convex shape that sits in a concavity in the pelvis. This acts as a ball and socket joint that allows the whole upper body to turn and tilt as one. However because the neck does not bend it has no need for muscles and nearly the whole of its cross section can be filled with an enlarged vertebral column for greater strength and more volume in the hollow of the tube. This is important because of the structure of the Highbrow brain.
At its core the Highbrow brain has the same basic structure of a hu brain, although one with all the neurological rewiring of the Su brain. What the highbrows have done which is different is ey have created an additional massive layer of the cerebral cortex. In the development of a foetal highbrow an outgrowth of the frontal lobes folds back over the brain, continues to grow past the parietal lobes and then down the back and sides of the brain until they collect under the temporal lobes. From there it further grows down into the hollow tube of the vertebral column. This enlarged neural network needs an expanded capacity for data traffic control and to do this an extension of the cerebellum has wrapped itself around the spinal cord and continued to grow down the enlarged vertebral canal. From there it can link up with and manage the workings of the grey matter in the vertebral tube.
Feeding, and cooling such a large brain was a major problem to solve. Even something as small as a baseline's brain takes about a third of that being's calorie intake to run. Su before em solved these problems just by increasing the efficiency of eir bodies but the Highbrows would have to use more extreme measures. On the other hand the Su are also generally superior, ey are superior in both mind and body and have the flexibility to adapt to whatever environment ey find emselves in. The Highbrows were willing to give up these non-mental advantages in favour of just maintaining eir brains.
These are some of the Highbrow physical traits and genemods:
Slightly larger size: Highbrows are about 15cm taller than near-baselines but you wouldn't know it if you looked directly into eir eyes. Highbrows have the same eyelevel as the average neb and below that eir bodies have the same proportions. (Although because of eir diet eir jaw structure could be much reduced) Eir additional height comes entirely from eir higher crown.
Enhanced respiratory system: Highbrow lungs have been redesigned to operate in a manner similar to Superior lungs, utilizing a counter-current exchange system for greater transfer of O2 and CO2. However ey also include a third lung-like structure. This "lung" is not involved in gas exchange, it acts solely as an air pump, pumping air up and around the brain housing for cooling. Because this third "lung" is not involved in gas exchange the air entering it does not need to be moistened but the lining of this lung can be wetted if cooling needs require it. Highbrow blood is about as efficient as Superior blood in capturing oxygen but ey don't operate as well as Superiors in low pressure or high altitude habitats and cannot hold eir breath for any great length of time.
Cold weather adaptations: With eir greater need for cooling Highbrows actually prefer lower temperature environments but ey do not have the extreme condition adaptations of Superiors. Ey cannot enter cryogenic stasis any more easily than nebs and do not have the anti-freeze blood proteins of Superiors. Nor can ey slow eir metabolic rate or enter hibernation like a Superior can. Nanostasis is still possible for long trips in space.
Digestion and metabolism: The early proto-Highbrows never intended eir new clade to be far from the comforts and supporting infrastructure of home and because the brain now takes up a significant portion of the chest and abdomen the digestive system could be, and in fact had to be, greatly simplified. Highbrows do not have the flexibility of diet that Superiors or even nebs have. Ey must consume easily digestible liquid foodstuffs with an optimum amount of nutrients, proteins, amino acids, and minerals to meet the environmental demands that their body is undergoing at the time. Ey much prefer a form of highly flavoured nanofactured syrup but ey can live on such things as mother's milk, blood and honey. Eir body fat ratio is minimal, for cooling reasons, so eir small stomachs act as reservoirs for eir between meals needs. Highbrows cannot go for long periods without eating and do not travel without access to either an autofab or a stockpile of eir liquid food.
Other enhancements: Highbrows have all of the mental and sensory enhancements found in Superiors; minimal sleep needs, multi-tasking capabilities, enhanced focus, superior memory, observation and pattern recognition, slearning and a few others but ey do not have eir enhanced musculature or biologic optimization.
Reproduction: Highbrows have had to resort to external foetal development; neogen exo-wombs and the like. This is because not only do infant Highbrows have a head/vertebral column structure that only a gengineered mother clade could pass but also because the housing for the brain in eir abdomens leaves no room for a foetus to grow there. Highbrow females are capable of 'carrying' eir baby but not in any way that evolved on old Earth. Highbrow babies are only carried internally for eight weeks, to the end of the embryonic stage. After this the foetus is pre-birthed.
In pre-birthing the foetus is delivered while still inside the embryonic membrane, which by this time has thickened into leathery egg-sack. This egg-sack, which grows with the foetus, remains connected to the mother by way a placenta and an umbilical cord that passes into the female's body through her vagina. After pre-birth a temporary cleft forms in the wall of her vagina, which the umbilical cord seats itself in. The vagina wall then encloses around the umbilical cord for the remainder of the foetus's development. The egg-sack has two long tentacle-like projections about the top that can be used to hang the egg-sack around the mother's waist, neck (over the shoulder) or any convenient limb. Highbrow fathers are noted for carrying the weight of the egg-sack whenever ey walk with eir mates. This external pregnancy is actually about twice as long as a full term baseline pregnancy, the foetus needs this additional time for the growth of its enlarged brain. However during the last three months the egg-sack thins and the baby can observe the world it will be born into.
Most Highbrow mothers prefer to carry eir babies emselves but eir external pregnancy makes a transfer to an exo-womb or other such thing a very easy process. The egg-sack even has a yolk-sack to keep the foetus fed if blood flow through the umbilical cord should be temporarily interrupted.
Society and Culture Highbrows adapt quite well to whatever society or culture will have em but most still live in the Federation. (the Terran Federation as it is now called) However there is one cultural aspect that sets em apart wherever ey go, the Test. The competitive natures that created eir clade have been focused into the Test, a contest that was deliberately patterned like a higher education entrance exam from the pre-Tranquility era. Once a year each Highbrow enters a small room sealed off from all electronic aids or communications and sits at a simple desk. The desk has only three things upon it; a small stack of papers with a long list of random problems and questions typed on them, an old fashioned pencil and a tall stack of blank paper to write the answers upon. The problems and questions are supplied by other Highbrows, other Superiors, superbrights and even sometimes by hyperturings and are meant to challenge both the knowledgebase of the testee and eir problem solving abilities. Rewards are given for high scores and the overall goal of the Test is to force eir culture towards organic ascension. And ey have come very close.
About four thousand years ago a Highbrow female by the name of Janasa Bree took the Test and while trying to solve one problem provided by a hyperturing she had an epiphany and entered a fugue state. Within minutes she had written down the correct answer to that problem and continued on to answer seven more before she regained her senses. Further inquiry showed she could not explain her answer or how she got it and it would take nineteen years for her to repeat this event. Five years after that she had her third epiphany, two years later - her fourth and the following year - her fifth. Special tests were set up for Janasa and it was found she could now enter a fugue state at will and answer a transapient level question correctly four times out of seven. There are similarities to what Janasa did in sophonts known as transavants but where a transavant is only "partially" ascended beyond eir base toposophic level and has only one or a few "spikes" of transapient expertise in very specific areas Janasa could "temporarily" ascend into whatever area of expertise was needed to answer the question she had placed in front of her. Within three years of this discovery Janasa had set up a School for Epiphany Studies (SES) and today about five percent of the Highbrow population can enter a fugue state at will and correctly solve a transapient level problem two out of three times. Ey have also gained an intuitive ability to control and maintain transapient level technology even when that tech is not modosophont-friendly.
The Highbrows have used this to advance the standing of eir clade in the Terragen Sphere and often send members out to the Edge to help developing worlds get a good start before any true transapients arrive and take control. To safeguard against providing wrong answers these SES students travel in small groups and only release an answer ey come up with if ey have a consensus of it being correct.
Technology Although the SES students have an intuitive ability to control and maintain transapientech ey cannot create it and the foundation of Highbrow society is primarily high tech. With eir massive neural network Highbrows are easily superbrights (ey actually like to call emselves neo-superbrights) and if a superbright has a toposophic level of SI:0.9 then a Highbrow can reach SI:0.99 with the median being SI:0.95. Highbrow technology therefore focuses on the high end of the high tech level; advanced mesotech and nanotech. But ey also show an interest in older forms of technology like the insect-tech that was abandoned in the second century A.T. and it is rare for a Highbrow not to have created eir own hive or nest as a child. Indeed, with eir special dietary needs having a beehive to supply em with honey just made good sense.