as being specifically feminine. These ideas of femininity are usually biologized and are often preoccupied with psychological characteristics, such as nurturance, empathy, support, and non-competitiveness, etc. Feminist theorist Elizabeth Grosz states in her 1995 publication Space, time and perversion: essays on the politics of bodies that essentialism "entails the belief that those characteristics defined as women's essence are shared in common by all women at all times. It implies a limit of the variations and possibilities of change—it is not possible for a subject to act in a manner contrary to her essence. Her essence underlies all the apparent variations differentiating women from each other. Essentialism thus refers to the existence of fixed characteristic, given attributes, and ahistorical functions that limit the possibilities of change and thus of social reorganization." Gender essentialism is pervasive in popular culture, as illustrated by the #1 New York Times best seller Men Are from Mars, Women Are from Venus, but this essentialism is routinely critiqued in introductory women's studies textbooks such as Women: Images & Realities. Starting in the 1980s, some feminist writers have put forward essentialist theories about gender and science. Evelyn Fox Keller, Sandra Harding, and Nancy Tuana argued that the modern scientific enterprise is inherently patriarchal and incompatible with women's nature. Other feminist scholars, such as Ann Hibner Koblitz, Lenore Blum, Mary Gray, Mary Beth Ruskai, and Pnina Abir-Am and Dorinda Outram have criticized those theories for ignoring the diverse nature of scientific research and the tremendous variation in women's experiences in different cultures and historical periods. In historiography Essentialism in history as a field of study entails discerning and listing essential cultural characteristics of a particular nation or culture, in the belief that a people or culture can be understood in this way. Sometimes such essentialism leads to claims of a praiseworthy national or cultural identity, or to its opposite, the condemnation of a culture based on presumed essential characteristics. Herodotus, for example, claims that Egyptian culture is essentially feminized and possesses a "softness" which has made Egypt easy to conquer. To what extent Herodotus was an essentialist is a matter of debate; he is also credited with not essentializing the concept of the Athenian identity, or differences between the Greeks and the Persians that are the subject of his Histories. Essentialism had been operative in colonialism as well as in critiques of colonialism. Post-colonial theorists such as Edward Said