The book argues that the evolutionary processes that are observed operating on Earth are universal, and a necessary requirement for the presence of complex life on any planet.

The book has been praised by critics for its accessibility and engaging conversational tone,[1] and described by Richard Dawkins as "A wonderfully insightful sidelong look at Earthly biology".

The book draws on the work of paleontologist Simon Conway Morris on convergent evolution,[9] and on Universal Darwinism, popularised by Richard Dawkins.

[14] Professor Lewis Dartnell, writing in The Times, summarised, "Pondering scientifically on the concept of the extraterrestrial, of universalities and alternatives, is to hold a full-length mirror up to ourselves.

"[15] In The Sunday Times, titled Using Darwinism to imagine what extraterrestrials may really be like James McConnachie wrote, "Arik Kershenbaum is a Cambridge zoologist who wants to prepare us for first contact.