and the patterns found on elephant bones from Bilzingsleben in Thuringia may have been produced by Acheulean tool-users such as Homo erectus prior to the start of the Middle Paleolithic period. Activities such as catching large fish and hunting large game animals with specialized tools indicate increased group-wide cooperation and more elaborate social organization. In addition to developing advanced cultural traits, humans also first began to take part in long-distance trade between groups for rare commodities (such as ochre (which was often used for religious purposes such as ritual)) and raw materials during the Middle Paleolithic as early as 120,000 years ago. Inter-group trade may have appeared during the Middle Paleolithic because trade between bands would have helped ensure their survival by allowing them to exchange resources and commodities such as raw materials during times of relative scarcity (i.e., famine or drought). Social stratification Evidence from archeology and comparative ethnography indicates that Middle Paleolithic people lived in small, egalitarian band societies similar to those of Upper Paleolithic societies and some modern hunter-gatherers such as the ǃKung and Mbuti peoples. Both Neanderthal and modern human societies took care of the elderly members of their societies during the Middle Paleolithic. Christopher Boehm (1999) has hypothesized that egalitarianism may have arisen in Middle Paleolithic societies because of a need to distribute resources such as food and meat equally to avoid famine and ensure a stable food supply. It has usually been assumed that women gathered plants and firewood and men hunted and scavenged dead animals through the Paleolithic. However, Steven L. Kuhn and Mary Stiner from the University of Arizona suggest that this sex-based division of labor did not exist prior to the Upper Paleolithic. The sexual division of labor may have evolved after 45,000 years ago to allow humans to acquire food and other resources more efficiently. Nutrition Although gathering and hunting comprised most of the food supply during the Middle Paleolithic, people began to supplement their diet with seafood and began smoking and drying meat to preserve and store it. For instance the Middle Stone Age inhabitants of the region now occupied by the Democratic Republic of the Congo hunted large long catfish with specialized barbed fishing points as early as 90,000 years ago, and Neandertals and Middle Paleolithic Homo sapiens in Africa began to catch shellfish for food as revealed by shellfish cooking in Neanderthal sites in Italy about 110,000