The Mariposa colony was an Earth colony located on the class M planet Mariposa, located in the Ficus sector. The colony was established in the mid-22nd century from the remains of the colony ship SS Mariposa, the colony's namesake.
Although originally intended to be established by a group of technology-savvy scientists, this all changed when the Mariposa began its planetary descent. As the ship attempted to land, the hull of the ship was breached and only five of the original colonists survived.
Since the colonists knew that two women and three men could not sustain a society, they looked to science to survive and turned to cloning. Future generations later referred to them as the "progenitors".
In 2365, Starbase 73 picked up an SOS from somewhere within the Ficus sector; Starfleet requested that the USS Enterprise-D investigate. The Enterprise determined that the source of the SOS was Bringloid V, home planet of the Bringloidi, and sister colony of the Mariposa colony.
It was later learned that the second Mariposa colony existed, and was located a mere ½ light year from Bringloid V. The Enterprise visited the Mariposan colony, only to discover a population of clones that were suffering from replicative fading. The Bringloidi, who were otherwise homeless, and the Mariposans decided to solve both of their problems, and reunify on Mariposa.
Since only thirty couples were available between the two groups, which was technically enough to create a viable genetic base, it was necessary to broaden the base for a safer and healthier society. This meant that each woman, from both groups, had to have at least three children by three different men. This, however, also meant that monogamous marriages would not be possible for several generations. (TNG: "Up The Long Ladder")