The Deltans were a humanoid species which originated from the planet Delta in the Alpha or Beta Quadrant. The Deltan government was the Deltan Union and they were members of the United Federation of Planets. (ST reference: Star Charts)
Deltans largely resembled Humans with the exception of having no surface hair except for eyebrows, lashes, and (occasionally) a very thin layer of soft down along arms and legs. They are, on the average, slightly slimmer than Humans, and their cheekbones, eye shapes, and jawlines are slightly more symmetrical, Humans (and many other humanoid species) often find Deltans quite attractive. (Decipher RPG module: Starfleet Operations Manual) Deltans were telepathic and empathic, allowing them to sense other peoples' emotions and administer medical aid by absorbing and minimizing pain. This trait made Deltans excellent medical personnel.
Deltans were perhaps best known for their high sexuality, both sexes emitted some of the most potent pheromones known to Federation science. As a result, Deltans were something of natural aphrodisiacs, most intensely among their own race, but with a strong effect on most other humanoid species. Because of this Deltans swore an "oath of celibacy" when serving in Starfleet, they also developed chemical applications to diminish their pheromonal effect. To limit exposure to Deltan pheromones, off-worlders are usually not permitted to visit Delta IV itself, instead being restricted to the planet's moons Seyann and Cinera (TOS movie: Star Trek: The Motion Picture; ST references: The Worlds of the Federation, Star Charts), or given an inhibitor shot. (DTI novel: Watching the Clock)
The Deltan oath of celibacy served not only to curtail sexual promiscuity with other races but also ensured the safety of non-Deltans; the long evolution of the Deltan race not only heightened their sensuality but has also resulted in the sex act becoming a complete union in which both body and mind are shared. For Deltans this was natural and pleasant, but the experience of actually becoming part of another person's mind almost always incapacitates a human partner. It was sometimes said that a non-Deltan who entered into a physical relationship with a Deltan risked insanity. (TOS novelization: Star Trek: The Motion Picture)
In 2141, the ECS Horizon made first contact with a Deltan starship. When the Deltans told the humans that they were from planet Dhei of the star Lta, the Horizon crew marked it in their star charts as Delta. (ENT episode: "Bound", DTI novel: Watching the Clock)
In 2182, the Deltans made first contact with the Andorians, the Deltan sage Niro guided the planet through its tumultuous decades from first contact to Federation membership, developed the Oath of Celibacy and writing much of Deltans' modernized legal code. (Decipher RPG module: Starfleet Operations Manual)
- The Enterprise episode "Bound" establishes Human contact with the Deltans as early as 2141. Star Charts claims the Deltans became warp-capable in 2223 and joined the Federation in the same year.
Following the Deltans becoming full members of the Federation in 2259 Starfleet teams were assigned to Delta IV. The Deltan Ilia worked closely with these teams and formed a strong attachment to the Human Willard Decker. The two later served together briefly on the USS Enterprise before both were reported, "missing in action," after the Enterprise encountered the V'Ger probe in 2273. (TOS novelization: Star Trek: The Motion Picture)
In 2368, stardate 45635.2, the Deltans fell victim to an attack on their homeworld by the Borg/Cybermen alliance. Delta IV was overwhelmed in a matter of minutes, forcing its prime minister to order a planetary evacuation well before Starfleet's defensive task force could arrive. (TNG - Assimilation² comic: "Issue 1")
In late 2379, the Deltans petitioned to the newly elected Federation President Nan Bacco for aid in repairing their ailing water reclamation system. They liked the design of the system on Gault; however, the system had been designed by the Carreon, who did not wish the Deltans to use it. (TNG - A Time to... novel: A Time for War, A Time for Peace)
Delta IV's unpredictable tides and otherwise inhospitable ecology have promoted a culture at once polyglot and unified. Although many microcultures evolved throughout the expansive planetary chain of island archipelagos, they could never remain isolated long enough to develop either xenophobia or devastating cultural and technological advantages over one another. To forestall inbreeding, the island-bound Deltans also cultivated an extremely open sexual culture. Indeed, stranded mariners were often adopted into large group amours in order to refresh local gene pools. Brought together by ties of sex and geography, Deltans learned to peacefully coexist and relate well, by necessity. With the bountiful, renewable resources of so flourishing a natural environment, and a low species birthrate, wars over resources were almost unknown among the Deltans. (Decipher RPG module: Starfleet Operations Manual)
The Deltans were also drawn to cultural unity by their genetic predisposition toward empathy along with related psionic abilities. The capacity to experience another's suffering rendered violence and armed conflict anathema, and even excessively hurtful personality conflict and quarrel, unthinkably impolite. Yet ordinary social hypocrisy was impossible due to the intense Deltan pheromones and acute sensitivity thereto, rendering Deltans so transparent to one another, emotionally. And so, their culture evolved toward a remarkable global ideal of supportive, nurturing behavior founded upon time-honored Deltan sexual openness. A deep-rooted sense of species and personal security remains unshaken by their subsequent contact with the Andorians and later other starfaring cultures of the Beta Quadrant. Their greatest concession to existence in a dangerous galaxy was the adoption of the renowned Oath of Celibacy out of necessity and good manners when dealing with those whom they came to regard, perhaps with somewhat patronizing deference, as less sexually-mature species and cultures. (Decipher RPG module: Starfleet Operations Manual)
While ST reference: Star Charts shows the Deltan homeworld in the Alpha Quadrant, the Decipher RPG module: Starfleet Operations Manual states this is a Beta Quadrant planet's civilization. For the purposes of this wiki, the civilization is categorized as being from one of the quadrants without specification as to which.