Around the second century BC the first-known city-states emerged in central Myanmar. The city-states were founded as part of the southward migration by the Tibeto-Burman-speaking Pyu city-states, the earliest inhabitants of Myanmar of whom records are extant, from present-day Yunnan. The Pyu culture was heavily influenced by trade with India, importing Buddhism as well as other cultural, architectural and political concepts which would have an enduring influence on later Burmese culture and political organisation.
From what people have were the first records known to be existent derived from? 
from present-day Yunnan