A stage that is imperative in any archaeological process is the reconstruction of the physical environments in which a particular segment of the archaeological record was formed. Climates and the world's geomorphology – the shape and constituents of land surfaces – have changed greatly over the past several million years of human history, and each archaeological analysis begins with an effort to reconstruct the physical world of the culture being analyzed. Ancient climates can often be reconstructed from floral and faunal remains. The study of animal remains, or faunal analysis, is a complex field in which, in most cases, the archaeologist is trying to reconstruct human diet and local environments. Faunal analysts usually count the numbers and kinds of animals represented by the remains they find, and then use statistical methods to estimate the food values, ages, and sexes of the animals being exploited. The prehistoric record of the meat-eating habits of early humans is far from clear about the prevalence of scavenging. One faction of prehistorians argues there is evidence that early humans were primarily scavengers who found the remains of animals killed by lions and other carnivores, and butchered them. Another faction disagrees and proposes that early humans hunted for their own meat. Marks left by humans cutting up animals with stone tools are now being analyzed to help distinguish between cases in which people butchered animals they had killed themselves and those in which they butchered animals they scavenged from kills of other animals. Throughout human history, plants have been our main source of food, and so floral analyses – studies of the remains of plants – are an extremely important part of archaeology, particularly in studies of how domesticated plants and animals and agricultural economies evolved. Carbon is chemically quite stable, so charred plants (plants converted to charcoal or carbon) and seeds preserve well. Carbonized plant remains can be retrieved by flotation: excavated sediments are mixed with water or some other fluid and the charred plant fragments rise to the surface, where they can be skimmed off and identified. The importance of such analyses lies in the fact that these plants indicate much about the climates and vegetation of the periods in which the animals lived. For example, there are debates about when and where various animals were domesticated. If phytoliths (tiny mineral particles formed inside plants) of domesticated grains are found on the teeth of these animals, the probability is high that they were part of an agricultural economy. Human bodies are also valuable sources of information for archaeologists, particularly if the bodies are well preserved. For example, eleven naturally mummified bodies were found in beach sand in northern Chile and date to about 1000 B.C. When they were analyzed, it was found that one of them was a coca leaf chewer (the earliest known), while other bodies showed the changes of the bones of the inner ear that are characteristic of people who spend a lot of time diving in cold water. In addition, they had the kinds of dental problems and missing teeth associated with the sticky starches of an agricultural diet – although about 40 percent of their diet came from marine resources. A rapidly growing technical specialty within archaeology is geoarchaeology, which combines archaeological and geological analyses. Geology and archaeology form a natural marriage in many obvious ways because both disciplines are concerned with the alteration of natural landscapes. Glaciers, changing rainfall patterns, and many other natural forces cause changes to landscapes, and of course, so do people. Geologists are broadly concerned with ancient physical environments, and archaeologists require knowledge of these environments to interpret their finds. Geoarchaeological analyses involve many different kinds of questions and techniques. In the Egyptian Delta region, for example, many of the earliest communities were built on large sand-and-gravel mounds created by the Nile River as it deposited the sediments it carried. But many of these communities have been buried under many meters of sediments from numerous ancient floods since that time and by other factors as well. Moreover, the streams feeding into the Nile River in the delta have changed course many times, leaving a maze of crisscrossed buried river channels. Finding these buried sand-and-gravel mounds and the archaeological sites on them often requires complex geological analyses involving special digging, satellite image analysis, and many other techniques.