For questions about the long-term change of a specific species, type of creature, or trait, usually through the process of natural selection and reproduction. Ideal questions focus on traits, not entire creatures. Consider also [creature-design].
Evolution is the theory, put forth by Charles Darwin in his book On the Origin of Species, that species change over long periods of time.
This is for questions that have to do with how certain species and/or traits evolve, why one trait might become dominant, or how certain traits could influence the species as it continues to evolve. It may also include what types of environments would encourage or support the evolution of different traits.
Questions using this tag that seek to understand what evolutionary pressures, conditions, or environments would bring about or favor the development of a specific trait must identify the purpose, value, or reason the proposed trait exists. Questions seeking evolutionary justification for a trait that is presented merely as an aesthetic (e.g., my creature looks like...) risk being closed for needing more details.
Questions should remain as focused as possible. Users should avoid presenting an entire life-form and asking how that creature in its entirety could evolve as specific traits of that life-form would evolve for very different reasons than others. Ideally, questions using this tag are focusing on individual traits.