The (gross) first third discusses the basics. Geology and (later) Biochemistry of the nascent planet Earth, the first reproductive molecules and DNA as the basis of life on Earth: What is it, life? What is consciousness, spirit, the self?
The rest of the book considered (human) apes, and makes clear through case studies that they not "just animals" are.
A thread on the ratio of men to animals and especially the monkeys: What makes us different? Anatomy? Culture, faith or morals? Technology? Piece by piece will be presented individual criteria and their representatives and opponents. Sagan and Druyan then take each argument apart and show that it is far from easy to say, what then makes us "human". In the end it becomes clear that the difference just is not clear, and that it might significantly makes more sense to see the primates as a larger group and draw no definitive dividing line between us and "them" want to.
Linguistically sofa is not Sagan's greatest triumph (which is why I do not give all five stars). Anyone who has read "Cosmos" or "Contact", knows to what heights Sagan was able and his later works can miss some of it. Still, he knows how the reader without ramblings serious scientific content and - to convey, a taste for it - especially. Sagan's academic background, incidentally, a very positive side effect to everything and everyone good references are present, which represents more than 40 of the last pages of the book.
Who always wanted to know a bit more about chimpanzees, bonobos and gorillas, the sofa is sincerely recommended. Only if you then still can go with a clear conscience at the zoo the ape enclosure, I doubt it.
