In archaeology and art history the appearance, and sometimes disappearance, of large or monumental sculpture in a culture is regarded as of great significance, though tracing the emergence is often complicated by the presumed existence of sculpture in wood and other perishable materials of which no record remains;  The totem pole is an example of a tradition of monumental sculpture in wood that would leave no traces for archaeology. The ability to summon the resources to create monumental sculpture, by transporting usually very heavy materials and arranging for the payment of what are usually regarded as full-time sculptors, is considered a mark of a relatively advanced culture in terms of social organization. Recent unexpected discoveries of ancient Chinese Bronze Age figures at Sanxingdui, some more than twice human size, have disturbed many ideas held about early Chinese civilization, since only much smaller bronzes were previously known. Some undoubtedly advanced cultures, such as the Indus Valley civilization, appear to have had no monumental sculpture at all, though producing very sophisticated figurines and seals. The Mississippian culture seems to have been progressing towards its use, with small stone figures, when it collapsed. Other cultures, such as ancient Egypt and the Easter Island culture, seem to have devoted enormous resources to very large-scale monumental sculpture from a very early stage. The collecting of sculpture, including that of earlier periods, goes back some 2,000 years in Greece, China and Mesoamerica, and many collections were available on semi-public display long before the modern museum was invented. From the 20th century the relatively restricted range of subjects found in large sculpture expanded greatly, with abstract subjects and the use or representation of any type of subject now common. Today much sculpture is made for intermittent display in galleries and museums, and the ability to transport and store the increasingly large works is a factor in their construction. Small decorative figurines, most often in ceramics, are as popular today (though strangely neglected by modern and Contemporary art) as they were in the Rococo, or in ancient Greece when Tanagra figurines were a major industry, or in East Asian and Pre-Columbian art. Small sculpted fittings for furniture and other objects go well back into antiquity, as in the Nimrud ivories, Begram ivories and finds from the tomb of Tutankhamun. Portrait sculpture began in Egypt, where the Narmer Palette shows a ruler of the 32nd century BCE, and Mesopotamia, where we have 27 surviving statues of Gudea, who ruled Lagash c. 2144–2124 BCE.