This tag identifies questions related to creating an alien biology that may be close to or far removed from Earthly biology, but still reflect what science knows about biology. This tag implies the use of the Science-Fiction tag. Use the Science-Based or Hard-science tags to impose greater scientific restrictions (see warning in tag wiki). The goal of this tag is to answer the question using what science humanity knows.
Xenobiology describes a form of biology that is not familiar to science and is not found in Earthly life. Novel biological systems and biochemistries that differ from the canonical DNA-RNA-20 amino acid system, which can include variations on the same these (e.g. different amino acids), totally different systems (such as the SF staple of silicon-based life). (Source)
Questions tagged with the Xenobiology tag should ask about biochemistry, biology, physiology, or chemistry as it relates to alien life. This tag cannot be used with the biology tag.
Questions relating to xenobiology do not ask about the aesthetics of a creature or how it interacts with its environment, but ask about the rationale that gives the creature life. Questions about biology-realated aesthetics or environmental interaction should use the creature-design tag.
Warning: Despite defaulting to science-fiction, this tag seeks already to use what science humanity knows to answer the question. However, humanity has not found life anywhere other than on Earth and studies into the possibility of life not natural to Earth are in their infancy. Users should understand that it's rarely possible to fully rationalize proposed alien life.
Therefore, users seeking to make their fantastic alien beings "as realistic as possible" are warned to avoid using the science-based and hard-science tags unless they have performed the necessary research to ask a science-based or hard-science question. If you choose to use either of those tags anyway, you are required to explain your research and explain why it failed to answer your question. Questions tagged with science-based or hard-science that fail to provide those two explanations will have the tags removed.
