Andorian/Gender and Reproduction
Andorians have 4 genders, 2 of which resemble males and 2 of which resemble females. These are called Thaan, Chan, Shen and Zhen. This can result in some confusion among outsiders. Sometimes it is difficult to tell what gender an Andorian is on sight. This is especially true as a chan can appear to be feminine and a shen can appear to be masculine.
A Thaan has internal testes, retractable penis and produces sperm to fertilize the egg of a Shen.
A Chan has internal testes, retractable penis and produces sperm to fertilize the egg of a Shen.
A Shen has a retractable ovipositor which they use to transfer the fetus from their uterus to the pouch of a Zhen. They also have a vagina, ovaries and uterus. They receive the sperm, produce the egg which then develops into a embryo and then transfer it to the Zhen's pouch once it has developed enough to make the transfer safely.
A Zhen has a vagina which is only useable for pleasure, not reproduction. They also have 4 teats on their lower abdomen and the ability to produce a pouch that is used to house the transferred embryo while it grows.
The gender determining chromosomes are called S, C, and T (rougly analogus to the Terran X and Y). Each Andorian has three of these chromosomes and the combination determins gender. The individual is Shan if they have SSS, Chan if they have SSC, Thaan if they have SST, and Zhan if they have SCT. Each gamete contain only one of the three. Shan eggs always have a S chromosome. Thaan and Chan sperm have a 50% chance of containing a S, or either a T or C respectively. The reason its not 33% chance of an S is because during early development, the second S chromosome in the Thaan and Chan undergoes and chemical change that isolates it from the other chromosomes and is expessed from the cells during meiosis. Although punnant squares are usually used to show the genotype probabliliy of offspring, it works on the same prinipal for chromosomes as far a gender is related.
With the S given by the Shan ommited because it is present in all genders. His produces an exact 1/4 chance of a child being every gender. The Zhan does not contribute any genetic material. This is because by the time the embryo is transferred to the Zhan, it is to developed to the point that it will not accept new genetic material into all of its cells.
In order for Andorians to produce a child it takes 1 of each gender. They each have a specific role to play. This starts with the Thaan fertilizing the Shen's egg. Then the Chan has to fertilize it next. The reason for this is that the 2 males, the Thaan and the Chan each have 1/4 of the necessary genetic material needed to create a child. The Shen has the other half with in her egg.
Once the egg has developed into a fetus it has to be transferred to the Zhen. This is because only the Zhen can nurse the young. When the Shen becomes pregnant special glands along the Zhen's spine become active. They will secrete a membrane that forms a pouch around the lower torso. At this time the 4 teats on the Zhen's lower abdomen will start to form milk. Unlike Humans these do not result in rounded breasts. The inner lining of the pouch produces a thick gel that will protect the baby while it nurses until it is mature enough to survive outside of the pouch.
Once the baby has emerged from the pouch the Zhen will come out of protective seclusion. Her pouch will dry up and flake away. The other 3 bondmates will then assist by rubbing her with oils and help to peel off the remains of the now useless pouch. Due to the fact that Andorian fertility periods have been slowly getting shorter they will try to conceive as many children as possible during this period and since fewer viable children have been born the Andorians have been forced to arrange bondings among genetically compatible members of their society. This has replaced allowing the young people to pick their bondmates.
As with most humanoid races, most Andorians will experiment with sex at puberty. Since their fertility period is so short it is impossible to produce offspring before or after this time. If they are found to be genetically acceptable they will generally be bonded by the age of 23.
Due to the requirement of four parents in the reproductive cycle and the usual production of less than four offspring, the Andorian species is in decline - the Andorian Science Institute has been hard at work exploring possible solutions to this problem.
The most promising form of research has been into altering the Andorian chromosome #17. It is believed that by altering this chromosome, they could increase the length of fertility considerably, thus increasing the number of years during which conception would be possible.
Another area of research is into the possibility of altering the way the gametes divide in the body. If successful, this would make both the Thaan and the Chan fully functional males with viable sperm. The long term implications for them as a race would be the elimination of the need for paired quads as their would eventually only be two sexes. However this research has produced great controversy within the Andorian society. It goes against all their customs and traditions. Many Andorians are outraged by this research and feel that any and all work into altering the four sexes should be stopped and destroyed.
Saf is a aphrodisiac and psychoactive chemical that is refined from a native Andorian plant. It does not replicate well and only grows successfully on their native homeworld of Andoria. It is used by Andorians during sex as it provides a number of benefits when it comes to pleasure and sexual function. Normally only sanctuary priests and priestesses are allowed to dispense it to bonded groups. It is generally only available by medical prescription.
It is illegal to possess Saf offworld and can be fatal to some non-Andorians. It has been used by some as a recreational drug and is still available on the black market. The Cardassians were known to use it during the Bajoran Occupation.