Evolving the Alien: The Science of Extraterrestrial Life (2002, published in the US, and UK second edition as "What Does a Martian Look Like?: The Science of Extraterrestrial Life") is a book about xenobiology by biologist Jack Cohen and mathematician Ian Stewart.
In this book Cohen and Stewart argue that any investigation of extraterrestrial life is too restrictive and unimaginative if it starts with the assumption that any advanced form of life must have similar characteristics to life on Earth, and must have evolved on a planet similar to the Earth (as in the rare Earth hypothesis). They suggest that it is possible to make a scientific and rational study of the possibility of life forms that are so different from life on Earth that we may not even recognise them as life in the first instance.