Ancient Humanoid

The ancient humanoids were a mysterious race of sapient, humanoid beings which existed 4.5 billion years ago, but are long extinct now. They were, as far as it's known, the first humanoid species to evolve in the Milky Way Galaxy, and it is thanks to them that all the other humanoids exist today.

History
A spacefaring civilization, the ancient humanoids traveled through the galaxy for many years, but were disappointed to find no other lifeforms similar to them. So they seeded the primeval seas of young planets, with DNA molecules "programmed" to direct evolution of life on these planets towards the emergence of organisms similar to those in the ancient humanoids' homeworld; including of course, a sapient humanoid race. This might explain not only why there are so many similar races in the galaxy, but why so many worlds have species similar to insects, reptiles, mammals, arachnids, and so on. Known planets seeded by the ancient humanoids include Earth, Indri VIII, Loren III, Ruah IV and Vilmor II, among others.

The ancient humanoids also recorded a computer program in the DNA, designed to display a holographic message to the future humanoid races who became advanced enough to find the clues to their origins, and cooperative enough to share the DNA samples with each other and "complete the puzzle".

It's possible to speculate that in most of the planets seeded by the ancient humanoids; insectoid, reptiloid and mammalianoid species evolved. However, thanks to the different environment conditions found on different planets; on some of them, sapience may have evolved in the insectoids or reptiloids, rather than mammalianoids. If this is true (there is no conclusive evidence that it is), it is possible that all life in the galaxy (with few exceptions) evolved in similar paths thanks to the ancient humanoids. This would explain for once why most lifeforms in the galaxy, even the non-humanoids, are so similar to each other: the majority of them are carbon-based, for instance, and share a bilateral symmetry and similar organs, like eyes, brain, digestive tract, limbs, etc.

Appearances

 * Star Trek: The Next Generation, s06e20, "The Chase" (1993)