Along with dividing up their project by theoretical emphasis, anthropologists typically divide the world up into relevant time periods and geographic regions. Human time on Earth is divided up into relevant cultural traditions based on material, such as the Paleolithic and the Neolithic, of particular use in archaeology.[citation needed] Further cultural subdivisions according to tool types, such as Olduwan or Mousterian or Levalloisian help archaeologists and other anthropologists in understanding major trends in the human past.[citation needed] Anthropologists and geographers share approaches to Culture regions as well, since mapping cultures is central to both sciences. By making comparisons across cultural traditions (time-based) and cultural regions (space-based), anthropologists have developed various kinds of comparative method, a central part of their science.