Image from Bernd Helfert
 [Interplanetary Age - recent] generic term for human or other biont in which the original genotype has been optimized for existence in extreme environmental conditions. Though many nearbaseline humans have modifications that allow them to survive in conditions outside the range suitable to baseline humans, tweaks are so radically changed that they are not interfertile with human baselines or nearbaselines. In the extreme cases they may have human-like form and psychology but lack any genetic or even biochemical overlap with the original human type.
 [Archaic or dialectical usage] A corporate modified human; usually the augmentation is part of the contract and is removed at the end of the employment.
Tweaks are humans who have used germline-engineering to adapt to extreme environments, or for aesthetic, cultural, or religious reasons. The process of adapting a human genetically to a hostile environment is one of the most common forms of pantropy. This is the largest division, both in absolute of numbers of individuals and in diversity of clades, of hominids. Traditionally it does not include those tweaks who are of human ancestry but who no longer look even remotely human. There are millions of different species of tweak. There are estimated to be some five quadrillion human tweak individuals of all kinds during the current era. Individual clades may in some cases number only a dozen members or in other cases run into tens of billions.
Background and Overview From the very beginning, the Terragen colonization of space and other worlds led to two distinct philosophical approaches: mastery versus adaptation, Promethean versus Protean. That ancient philosophical divide exists to this day.
The baseline and superior normals, and to a lesser extent the cyborgs, attempted to modify the environment as much as possible to suit their original Terragen biological nature: gravity of 1 G, an atmosphere 21% oxygen and 79% nitrogen at standard Old Earth pressure, temperature not too far from the average Old Earth temperature of 15 degrees Celsius, lighting comparable to that found on the surface of Old Earth, and so on. Everywhere the normals went, they tried to make that place like an imitation of the Earth they had left behind, and specifically of the portions of the Earth most comfortable to baseline humans. Even much later, after the Great Expulsion by GAIA, of nearly all Earth-bound baselines, they still insisted that every planet and biosphere should emulate Earth Normal standards.
In contrast, the tweaks (those in sense 1 above, not the employees of corporations, who might seek a return to "normal") believed that the best approach was to modify or evolve themselves to suit their environmental conditions. So on the Moon they adapted their physiology to one sixth gravity, on Mars to one third gravity and so on. In the asteroid belt and other microgravity habitats they actually altered their metabolic structure, musculature, and bone structure to survive indefinitely in a zero gee environment.
The first tweaks were those specifically adapted or designed as such, such as the space people, the merpeople, and the Martians, but by the later Interplanetary Age many hu groups were modifying themselves, taking up the biohack flame that had languished with the corporatisation of the original tweaks and biopunks of the Information Age.
Despite the best attempts of AI memegineers like Kilburn, the Anaxander Agent Clique, Silicon God, Mycroft, and 110001, human baseline fear and hatred of these new groups would sometimes flare up, and on occasion tweaks would return this in kind or develop supremacist groups of their own, although fortunately eruptions of violence were rare (cliological simulations have repeatedly shown that were it not for the efforts of the early hyperturings, the result would have been very different). The baselines feared and resented space-adapted superiors, who they felt to be stealing the future from them, and called the tweaks "apes" or "chimps" because of the modification of their feet into prehensile organs (very useful in zero-gee). Oddly, "ape" was also a favorite term of insult the tweaks tended to throw at the normal humans. Use of this term as an insult did not endear either party to ape provolves, of the day, and was a cause for tension between sophont apes and the tweaks.
The isolation of communities during the Dark Age after the Technocalypse of the mid 5th century resulted in rapid divergence between tweak and superior colonies. The availability of DIY gengineering and the often radically different environments and cultures of the different habs drastically accelerated the standard Darwinian process of genetic drift. After four or five centuries many of these populations were so strongly modified that they were unable to interbreed. They were not just nearbaseline clades but were as distinct from one another as members of a different species, genus, family or even order, so great were the genetic differences. Every habitat, asteroid, and comet-state, had its one or several unique guilds, races, subspecies, and species, and these in turn further cladized among themselves. Creating a common focus for this astonishing and often squabbling diversity was one of the tasks that the First Federation set itself, but was never able to fully realize.
Eventually the tweaks went on to colonize much of the frontier, while the Superiors congregated in the more established and comfortable centers of civilization, the nearbaselines made up the mass of the human population, and the original baselines became a rare and exotic minority, even a protected species in reserves.
Over time the distinction between tweak, superior, and nearbaseline humans has become more is difficult to make, and is often a matter of social convention or personal identification. Generally though a tweak is still defined as a human who is able to survive, thrive, and reproduce without technological assistance in environments that a human baseline could not, to the extent that e and is not fertile with typical nearbaseline stocks, and yet lacks the superbright intelligence and extraordinarily enhanced general abilities typical of superiors.
- Anakim - Text by Michael Walton
Common type of tweak that is adapted for higher than earth-normal gravity. There are many variants but all are similar in appearance and capabilities. They were originally designed to settle mineral-rich worlds with unusually deep atmospheres.
- Convocation, The - Text by Steve Bowers
A clan of vampire tweaks first encountered in Cableville in 8666 in the unlighted section known as the Dark.
- Daveth Tweaks - Text by Basu, based on original material by Anders Sandberg
A tweak species from the planet Daveth, extremely adaptable and militant that rose to prominence in the volume around the Coathanger Cluster, expanded with their feared habitat-raper ships at enormous speed in the period 5100-5340 before they were totally annihilated by the Dawn Mutual Protection Treaty Organisation.
- Deines - Text by M. Alan Kazlev
Wealthy social group or subclade of Radiation Nation that live on Hekufast.
- Europans - Text by Anders Sandberg, some additional content by M. Alan Kazlev
Highly derived aquatic tweak race, Sol System, 1st millennium A.T. to present.
- Extremophile - Text by M. Alan Kazlev
A rather chauvinistic term for any biological organism, whether terragen or xenobiont, natural or tweaked, that requires extreme (non-Earthlike) environments for growth or metabolism.
- Eyre, Kingdom of - Text by Anders Sandberg and M. Alan Kazlev
Tau Ceti II (Nova Terra) aquatic tweak kingdom.
- Genen, House Genen - Text by Anders Sandberg
Bioaugmented traditionalist superclade and House.
- Genetekkers, The - Text by M. Alan Kazlev
Early superior/tweak biocorporation culture and later superpower of the middle and late Interplanetary and Nanotech Age, internalized to the Jupiter moons and the outer Sol System, developed into a number of clades. A number of nearby star systems were colonized by Genetekkers. Some First Federation age Genetekkers became the Genen.
- Gigantes - Text by Omega Tyrant
Gigantes- A sub clade of highly cyborged and bioborged Nephilim designed to be able to engage in "riskier" activities.
- Highbrows - Text by AI Vin
Early tweak-su human clade with increased cranial capacity.
- Homo cosmoi / Space Adapted Human - Text by M. Alan Kazlev and Steve Bowers
Early microgravity-adapted tweaks.
- Human Low Gravity Tweaks - Text by Arik
Human clades geneered to thrive on low gravity worlds
- Humans - Text by M. Alan Kazlev; additions by Stephen Inniss
The term "human", or hu, is generally applied to Terragen near-baseline modosophont biont hominids, specifically Homo sapiens and closely related or derived species, who bear moderate bodymods, or none at all, and are not radically different from the original human stock in overall form and behaviour.
- Jötunn - Text by Michael Miller
Giant, vacuum-adapted human-derived clade.
- Keymales - Text by Steve Bowers
First developed by the GeneTEK megacorp in the Jovian League golden age, the Cryptokey geneline was additional to the male and female genome involved in ordinary sexual reproduction.
- Kobolds - Text by Steve Bowers
A clade of high gravity tweaks gengineered for life on the planet Sisyphos. A metre tall and the same wide. Despite their short stature, they are strong and hardy and capable of great feats of strength in Earth-like gravity regimes.
- Lazarus Longidae - Text by Steve Bowers and Michael Capriola
Tweak clade known to live for thousands of years. Named after a fictional character created by the Information Age novelist Robert A. Heinlein, who told Long's story as a series of memoirs. The Lazarus Longidae clade write all their long term memories down in very small thin leaved notebooks, use tiny shorthand ideogrammatic writing, and keep the notebooks in hundreds of small pockets in their overalls, moving all the notebooks around sequentially each time they fill one and throwing the oldest one away.
- Martian Tweaks - Text by Felipe Brando Cadavid, Arik and Steve Bowers
Humans adapted to the Martian environment.
- Megaptera - Text by Steve Bowers and A.J. Garth
Homo megaptera; whale sized merpeople from Zennor system in Libra. These water breathing adapts have powerful arms, a whale-like tail but no legs.
- Merpeople - Text by M. Alan Kazlev and Steve Bowers. Updated by Ryan_b 2016
Early aquatic tweak human clade.
- Methanoids - Text by Steve Bowers
Methane-respiring cold-adapted extremophile humanoids created by House Genen in the Zoeific Biopolity; very widespread and often actively involved in opposition to terraforming projects. Important faction in the Epp War.
- Pantropy - Text by Steve Bowers
The practice of adapting humans (and other bionts) to live comfortably in a planetary environment rather than attempting to change that environment to resemble the home world.
- Radiation Nation - Text by Anders Sandberg
Synclade of radiation-resistant human-derived bionts.
- Sailors of the Ebon Sea - Text by John Snead
Advanced vacuum-adapted clade.
- Soft Radnad - Text by M. Alan Kazlev
Members of the tweak synclade Radiation Nation who use highly enhanced DNA repair systems, often based on Deinococcus radiodurans and on Xenobacter mirabilis from Mykropht III.
- Space People - Text by M. Alan Kazlev
 (archaic) A common early term for Space Adapted Humans, still used by some descendants of the original clade.
 (Second Federation Era) A term for vacuum adapted tweaks, now rarely used.
- Sritht - Text by Liam Jones
Heavily derived eusocial hominid tweak/bioborg clade.
- Tro'el, Clade - Text by AI Vin
A clade of cold adapted humans living on ice moons.
- Vacc-Suckers - Text by Elliot Schutjer
A failed clade of early Interplanetary Era tweaks that were designed to operate in open space without protection.
- Vacuum Adapted Humans - Text by Anders Sandberg, with modifications by M. Alan Kazlev
- Vampires - Text by M. Alan Kazlev (with additions by Pran Mukherjee)
A human-derived clade based on human legends.
- Virds and Vats - Text by John Snead
Flying clades from Mazukata's Holiday.