Alien Lifeforms

Non-sentient alien life is relatively abundant throughout known space. There are currently 562 worlds within civilized space known to host native life; of these, 517 contain exclusively microscopic domains. The total number of life domains (each domain an example of life arising completely independently) is less than the total number of worlds that are considered to have native life. This is due to panspermia, an exchange of life between planets or moons via impact events where ejecta from one life-bearing world carries microscopic life to another by chance. There are several known instances of panspermia having occurred in the deep past of other star systems.

Several thousand other worlds beyond visited space have been confirmed to host life through remote observations. Several million more candidate worlds await definitive confirmation, requiring further analysis to determine if their biosignatures can be ruled definitively biological in nature. This task is made difficult by the volatility and unpredictability of unknown variants reacting to produce bizarre chemistry.

Read more: Alien biochemistry

Sentient Life

Sentient alien life is considered to be any life not native to Home which exhibits some semblance of either self-awareness or advanced problem-solving capability, although the exact definition can never be definitive. There is only one single known example of life that undeniably fits this classification, known as the Shaders.

The Great Filter

Before the discovery of the Shaders, humanity wondered not only whether it was alone in the universe, but why it appeared to be alone at all. Even conservative predictions for the frequency of life estimated that the universe should be teeming with advanced civilizations. After the discovery of the Shaders, and once simple and eventually complex life was discovered on other worlds, it was presumed that the development of sentience is the great filter through which so few domains of life are able to pass.