Earthlings is a report on the Earth compiled by aliens. Using this humorous concept, the authors present information about Earth (one of an infinite number of planets) and its inhabitants (not as unique as they would like to think they are) objectively using numerical data, avoiding judgments and analyses. The book shows readers that diversity is common and natural; it is intended to teach tolerance and understanding and to reflect together about who we, Earthlings, are and how we treat our planet.