Evolving the Alien: The Science of Extraterrestrial Life (published in the US, and UK second edition as What Does a Martian Look Like?

[1][2][3] The concept for the book originated with a lecture that Cohen had revised over many years, which he called POLOOP, for "Possibility of Life on Other Planets".

[4] Cohen and Stewart argue against a conception of extraterrestrial life that assumes life can only evolve in environments similar to Earth (the so-called Rare Earth hypothesis), and that extraterrestrial lifeforms will converge toward characteristics similar to those of life on Earth, a common trope of certain science fiction styles.

[6][5] In its review of Evolving the Alien, the London Review of Books commented that Cohen and Stewart's speculative approach is useful in exposing errors in conventional thinking, and is "painlessly educative" on the current state of the applicable sciences, but criticized their "naive optimism" with respect to future technological breakthroughs in human space travel.

[5] In his review for Nature, Lawrence M. Krauss admitted to not being completely sure of the book's intended goal and audience, but noted that it may serve as a counterpoint to arguments put forth in Peter Ward and Donald Brownlee's book, Rare Earth.