Ecology is the study of how all living things relate to each other and to their environment. In a natural ecosystem all things are connected in a balanced way. Most ecosystems today are altered by humans, intentionally (e.g. to produce things like timber or crops) or accidentally (e.g. by introducing new species or making others extinct). Are there parallels here in human societies? Are some societies (e.g. groups, cities, countries) in balance, working together for the good of all?