The triune brain is a model of the evolution of the vertebrate forebrain and behavior, proposed by the American physician and neuroscientist Paul D. MacLean. MacLean originally formulated his model in the 1960s and propounded it at length in his 1990 book The Triune Brain in Evolution.[1] The triune brain consists of the reptilian complex, the paleomammalian complex (limbic system), and the neomammalian complex (neocortex), viewed as structures sequentially added to the forebrain in the course of evolution. However, this hypothesis is no longer espoused by the majority of comparative neuroscientists in the post-2000 era.[2] The triune brain hypothesis became familiar to a broad popular audience through Carl Sagan's Pulitzer prize winning 1977 book The Dragons of Eden.