Sex at Dawn
 Sex at Dawn: The Prehistoric Origins of Modern Sexuality is a book dealing with the evolution of monogamy in humans and human mating systems. First published in 2010 it was co-authored by Christopher Ryan Ph.D and Cacilda Jethá MD (Portuguese pronunciation: [kɐˈsiɫðɐ ʒɨˈta]). In opposition to what the authors see as the 'standard narrative' of human sexual evolution they contend having multiple sexual partners was common and accepted in the environment of evolutionary adaptedness.