Genders (or sexes) were a type of biological variation between different members of the species. They were key to sexual reproduction, the creation of offspring. In many humanoid species, this involved a combination of two or more individuals' genetic material. It was also possible for members of certain species with compatible or related genetic structures to practice interspecies reproduction.
In many animal species, the female initiated the mating ritual. Captain Janeway reminded Tom Paris of this when they hyper-evolved into salamander-like species and produced offspring. (VOY: "Threshold")
Male and female gender
Many humanoid cultures had a two-sex system based around the division between male and female, or the masculine and the feminine, each of which contained a number of minor anatomical differences. One each of both sex, known as mates, were required to reproduce in a process called sexual reproduction. (TNG: "Where Silence Has Lease"; ENT: "The Crossing")
According to Counselor Deanna Troi, "Human males are unique. Fathers regard their sons as children, even into adulthood. Sons chafe against their fathers' perceived expectations." (TNG: "The Icarus Factor")
Some more-advanced lifeforms also maintained such distinctions. When two members of the Q Continuum chose to practice two-party reproduction, they manifested themselves in such a manner. (VOY: "The Q and the Grey") However, Q revealed a scornful attitude toward Human females when he discovered Humans in the Delta Quadrant a century sooner than expected: "This is what happens when you put a woman in the captain's chair!" (VOY: "Death Wish")
Upon first being created, a genderless Lal regarded the android's lack of gender as rendering itself "inadequate". Data told it this is why it ought to choose one, to complete its appearance. (TNG: "The Offspring")
William T. Riker referred to an Earth nursery rhyme, "What Are Little Boys Made Of?", which stated: "Girls are made from sugar and spice, boys are made from snips and snails... and puppy dog tails," to describe the "old-fashioned way of looking at the sexes" to the androgynous Soren. He later clarified that "physically, men are bigger, stronger" and that they "have different sexual organs." He also noted, "Men can't bear young." (TNG: "The Outcast") Worf once explained, "It is my understanding that in most Human families, the woman shares in the cooking." (TNG: "Time Squared") In Earth's past, it was noted that only landowners of a particular gender had any rights at all. (VOY: "Author, Author")
The planet Angel I was considered "an unusual matriarchal society" where the female was aggressively dominant, as well as larger and stronger than the male counterpart, in what was considered an arrangement most sensible and natural. (TNG: "Angel One")
Other variants of sex and gender
There were also various alien sexual makeups which consisted of different constructs or combinations of sexes:
- See: Androgyny
Androgyny, also known as being "genderless" or "neuter", was the absence of distinct genders. A number of androgynous species were known, including the Axanar, the Xindi-Insectoids, the Bynars, and the J'naii, among others. (ENT: "Fight or Flight", "Hatchery"; TNG: "11001001", "The Outcast")
When considering the health of Sluggo, a slug-like creature discovered by Hoshi Sato in 2151, she referred to it as a "she". However, Doctor Phlox questioned the identifier, stating, "We haven't been able to determine its gender yet, if it has one." (ENT: "Fight or Flight")
Hermaphroditic and transgender species
- See: Hermaphrodite
Hermaphrodism referred to having the characteristics of two or more sexes. Unlike androgynes, hermaphrodites could function as either a male or a female during sex, or undergo a functional transformation from one gender to another.
More than two sexes or genders
Some species had more than two sexes, or different capacities were assumed by sexes not conforming to the pattern of male/female bonding which seemed to be common throughout the galaxy.
According to T'Pol, "Tri-gender reproduction [was] not uncommon," while Phlox noted that, "Multi-gendered techniques [for reproduction] aren't always the same." For example, Vissians required three separate sexes to reproduce: male, female, and cogenitor. Phlox speculated that "the cogenitor provides an enzyme which facilitates conception," and it was later revealed by a Vissian that cogenitors were "only needed when a couple's trying to have a child," and made up a small percentage of the overall population, about three percent. (ENT: "Cogenitor")
- See: Neuter
At least one species, J'naii, though largely genderless, had some members self-identified as female or male, and showed attraction based on gender in others (e.g. Humans). For most of the J'naii this was considered a deviant identity, and gendered members of their species were subject to Psychotectic treatment that would render them genderless. (TNG: "The Outcast")
Kate Mulgrew as Captain Janeway was the first female lead actor of a Star Trek series. The first female captain seen on Star Trek was the Saratoga captain seen in Star Trek IV: The Voyage Home, played by Madge Sinclair. While Majel Barrett's character Number One was the first female first officer to appear in Star Trek, it was Nana Visitor's character, Kira Nerys, that was Star Trek's first female regular character to serve as first officer. The first pairing of a female captain and a female first officer serving aboard the same starship as each other was the USS Shenzhou's Philippa Georgiou and Michael Burnham in DIS: "The Vulcan Hello" and "Battle at the Binary Stars". (AT: "O Discovery, Where Art Thou?")
According to TNG: "Data's Day" and DS9: "Field of Fire", Andorian marriages typically involved four partners and Bolian marriages might include co-spouses. It was not revealed what, if anything, this said about the genders of the aforementioned species. Only male and female Andorians have been referred to on screen, and no on-screen Andorian child has been referred to as having more than two parents.
In ultimately unused dialogue from the writers' first draft script of ENT: "Dear Doctor", Dr. Phlox tried to reassure Hoshi Sato that his Pyrithian bat bit males only, but Sato wasn't so sure that the bat could tell the difference between genders.
Several non-canon novels and comics (such as the DS9 series) have portrayed Andorians as having four distinct sexes required for mating. Other novels portray other cultures having three or more sexes, such as Diane Duane's description of a Horta character as being an "orthomale type B4-A".