465: Don't Dismiss Astrobiology -- Chyba; et al. 308 (5721): 495f -- Science
Its aim is not just to find life but, rather, to both determine and understand the distribution of life in the universe through time. One extreme possibility is that life exists only on Earth, has never existed anywhere else, and will never be present beyond Earth's orbit. At the alternative extreme, life may have originated on multiple bodies in our solar system and may be ubiquitous beyond. No matter what the answer proves to be, astrobiologists will want to know how the actual distribution of life relates to the occurrence of different planetary environments. Hence, in addition to exploring for evidence of life beyond Earth, astrobiologists study the extreme limits to life, the conditions that make environments habitable, the origin and evolution of life on Earth, the processes responsible for the occurrence of habitable environments in our solar system, and the occurrence of planets and their habitability beyond our solar system.
Sounds like evolution is at play in astronomy, too.