One of three primary, discrete, and interrelated emotion systems in the brain for mating, reproduction, and parenting (the other two being attraction and attachment). Lust (Sex drive or the libido) is characterized by a craving for sexual gratification; it is associated primarily with estrogens and androgens. Lust evolved principally to motivate individuals to seek sexual union with an appropriate member of the species.
Fisher, H. (2000). Lust, attraction, attachment: Biology and evolution of the three primary emotion systems for mating, reproduction, and parenting. Journal of Sex Education and Therapy, 25(1), 96-104. doi: 10.1080/01614576.2000.11074334.