each other throughout their careers, perhaps leading to Picasso entering a new period in his work by 1907, marked by the influence of Greek, Iberian and African art. Picasso's paintings of 1907 have been characterized as Protocubism, as notably seen in Les Demoiselles d'Avignon, the antecedent of Cubism. The art historian Douglas Cooper states that Paul Gauguin and Paul Cézanne "were particularly influential to the formation of Cubism and especially important to the paintings of Picasso during 1906 and 1907". Cooper goes on to say: "The Demoiselles is generally referred to as the first Cubist picture. This is an exaggeration, for although it was a major first step towards Cubism it is not yet Cubist. The disruptive, expressionist element in it is even contrary to the spirit of Cubism, which looked at the world in a detached, realistic spirit. Nevertheless, the Demoiselles is the logical picture to take as the starting point for Cubism, because it marks the birth of a new pictorial idiom, because in it Picasso violently overturned established conventions and because all that followed grew out of it." The most serious objection to regarding the Demoiselles as the origin of Cubism, with its evident influence of primitive art, is that "such deductions are unhistorical", wrote the art historian Daniel Robbins. This familiar explanation "fails to give adequate consideration to the complexities of a flourishing art that existed just before and during the period when Picasso's new painting developed." Between 1905 and 1908, a conscious search for a new style caused rapid changes in art across France, Germany, The Netherlands, Italy, and Russia. The Impressionists had used a double point of view, and both Les Nabis and the Symbolists (who also admired Cézanne) flattened the picture plane, reducing their subjects to simple geometric forms. Neo-Impressionist structure and subject matter, most notably to be seen in the works of Georges Seurat (e.g., Parade de Cirque, Le Chahut and Le Cirque), was another important influence. There were also parallels in the development of literature and social thought. In addition to Seurat, the roots of cubism are to be found in the two distinct tendencies of Cézanne's later work: first his breaking of the painted surface into small multifaceted areas of paint, thereby emphasizing the plural viewpoint given by binocular vision, and second his interest in the simplification of natural forms into cylinders, spheres, and cones. However, the cubists explored this