 Maynard Smith published a book entitled "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.