With the appearance of iron weapons by the 3rd century BCE, the inhabitants of Mongolia had begun to form clan alliances and lived a hunter and herder lifestyle. The origins of more modern inhabitants are found among the forest hunters and nomadic tribes of Inner Asia. They inhabited a great arc of land extending generally from the Korean Peninsula in the east, across the northern tier of China to present-day Kazakhstan and to the Pamir Mountains and Lake Balkash in the west. During most of recorded history, this has been an area of constant ferment from which emerged numerous migrations and invasions to the southeast (into China), to the southwest (into Transoxiana—modern Uzbekistan, Iran, and India), and to the west (across Scythia toward Europe).