By the end of the Roman era, theories about a spherical Earth, latitudinal climatic zones, environmental influences on humans, and humans' role in modifying the Earth were established. They added to the Greek knowledge of the physical Earth and added information about different cultures they encountered or conquered. The Romans, un-like the Greeks, were empire builders and brought many different cultures under their control. Greek scholars were curious about the world, particularly the physical aspects, and collected information from traders and travelers. Physical and human geography are two great branches of the discipline, and their origins can be traced to the Greeks and later the Romans. Geography literally means "to describe the Earth," and the practical aspects of geography first arose among the Greeks, Romans, Mesopotamians, and Phoenicians. Conquest and commerce generated a need to know about the world and pragmatism was added long ago by traders and explorers. Humans' insatiable curiosity and the place-centered element within us gave birth to geography as an academic discipline. Places possess an emotional quality, and we all must belong somewhere. Even children possess qualities of geographers, creating carefully mapped realms in tiny places. They can think territorially or spatially and have an awareness of, and curiosity about the distinctive nature of places.