A fascinating and detailed examination of the evolution--and occasional devolution--of sexuality in microorganisms and more complex forms of life. Margulis and Sagan trace sex from its inauspicious beginnings in bacteria threatened by ultraviolet radiation to its intimate relation with the origin of mitotic division of nucleated cells. The origin of meiotic sex through cannibalism followed by centriole reproductive tardiness and the connection of cell symbiosis to sex and differentiation are explored.
"The authors have not only given us a new and exiting scenario for the evolution of sex,...

How do new species evolve? Although Darwin identified inherited variation as the creative force in evolution, he never formally speculated where it comes from. His successors thought that new species arise from the gradual accumulation of random mutations of DNA. But despite its acceptance in every major textbook, there is no documented instance of it. Lynn Margulis and Dorion Sagan take a radically new approach to this question. They show that speciation events are not, in fact, rare or hard to observe. Genomes are acquired by infection, by feeding, and by other ecological associations, and...