Maynard Smith published a book titled "The Evolution of Sex" which explored in mathematical terms, the notion of the "two-fold cost of sex". During the late 1980s he also became interested in the other major evolutionary transitions with the evolutionary biologist Eörs Szathmáry. Together they wrote an influential 1995 book "The Major Transitions in Evolution", a seminal work which continues to contribute to ongoing issues in evolutionary biology. A popular science version of the book, "The Origins of Life: From the birth of life to the origin of language", was published in 1999.