Evolutionary aesthetics refers to evolutionary psychology theories in which the basic aesthetic preferences of Homo sapiens are argued to have evolved in order to enhance survival and reproductive success. Based on this theory, things like color preference, preferred mate body ratios, shapes, emotional ties with objects, and many other aspects of the aesthetic experience can be explained with reference to human evolution. Aesthetics and evolutionary psychology Many animal and human traits have been argued to have evolved in order to enhance survival and reproductive success. Evolutionary psychology extends this to psychological traits including aesthetical preferences. Such traits are generally seen as being adaptations to the environment during the Pleistocene era and are not necessarily adaptative in our present environment. Examples include disgust of potentially harmful spoiled foods; pleasure from sex and from eating sweet and fatty foods; and fear of spiders, snakes, and the dark. All known cultures have some form of art. This universality suggests that art is related to evolutionary adaptations. The strong emotions associated with art suggest the same. Landscape and other visual arts preferences An important choice for a mobile organism is selecting a good habitat to live in. Humans are argued to have strong aesthetical preferences for landscapes which were good habitats in the ancestral environment. When young human children from different nations are asked to select which landscape they prefer, from a selection of standardized landscape photographs, there is a strong preference for savannas with trees. The East African savanna is the ancestral environment in which much of human evolution is argued to have taken place. There is also a preference for landscapes with water, with both open and wooded areas, with trees with branches at a suitable height for climbing and taking foods, with features encouraging exploration such as a path or river curving out of view, with seen or implied game animals, and with some clouds. These are all features that are often featured in calendar art and in the design of public parks. A survey of art preferences in many different nations found that realistic painting was preferred. Favorite features were water, trees as well as other plants, humans (in particular beautiful women, children, and well-known historical figures), and animals (in particular both wild and domestic large animals). Blue, followed by green, was the favorite color. Using the survey, the study authors constructed a painting showing the preferences of each nation.