The Medes and Persians were both Indo-European-speaking peoples and part of the broader Iranian groups. The Elamites have very different Mesopotamian roots.
The Medes and Persians moved south to the Iranian high plateau in the second millennium b.c.e., although exactly when is the subject of much debate. The Medes settled in the northern Zagros Mountains (Loristan in today’s Iran), a land of high mountains, rich valleys, and cascading rivers.
The Median capital of Ecbatana, today’s Hamadan, was situated at a critical point on the main road between Mesopotamia and the Iranian Plateau, from there leading around the Iranian central desert and eventually to China; as a result the Medes were well connected with the surrounding nations.
The Persians on the other hand initially settled slightly to the west of the Medes, but the first written records, from Assyria, find them in the southern Zagros Mountains, in the area north of the Persian Gulf, around Pars and the ancient Persian capitals of Pasargadae and Persepolis, an area away from the main trade roots.
During the period of Assyrian dominance in Mesopotamia in the eighth century b.c.e., Tiglath-Pileser III invaded the Zagros region twice, and Sargon II (721–705 b.c.e.) invaded it six times. The Assyrians were determined to control the trade routes to the east, and this meant keeping Media under their control; deportations of Median people are recorded 18 times in the Assyrian annals.
Sargon’s texts record 50 Median chieftains in the eighth century b.c.e., and if Herodotus is to be believed, it was not until the coming of the ruler Deioces in the early seventh century b.c.e. that the Median people became united, and Ecbatana was established as their capital.
The Medes struggled to throw off Assyrian overlordship, only finally succeeding after an alliance was struck between their king Cyaxares (c. 650–585 b.c.e.) and the resurgent Babylonians, an alliance that resulted in the destruction of the Assyrian Empire, following a successful joint attack on the Assyrian capital Nineveh in 612 b.c.e.
The extent of the Median Empire before its absorption into the Persian Empire under Cyrus II is not clear, although it appears that it stretched to the border of the ancient kingdom of Lydia, the center of modern-day Turkey.
The Persians played a subsidiary role to the Medes throughout the seventh century b.c.e., and during the reign of Cyaxares they became a subordinate kingdom. However, in the sixth century b.c.e. Cyrus led the Persians in a successful revolt and an eventual takeover of the Median Empire.
Although the Persians were the victors, the Medes had a special status within the Persian Empire, not only because they were similar peoples racially and linguistically, but also because Cyrus had both Median and Persian bloodline.
It seems that up until the time of Cyrus Persian was not a written language. As a consequence the cuneiform script used on the ancient monuments visible today at Behistun and Persepolis was most likely invented for the purpose, either in the reign of Cyrus or Darius I. Overall the evidence suggests that neither the Persians nor the Medes were literate, and in fact the main written language of the empire was Elamite.
Whereas the Medes and the Persians were of one tribal root, the Elamites, the people of the southeast corner of the Mesopotamian plain were linguistically and racially Mesopotamian. The first recorded history of the Elamites is in the early third millennium b.c.e.; at this time they had their own form of writing, proto-Elamite.
During the third and early second millennia b.c.e. the Elamites were rivals with the Sumerians, and though they married their sons to Sumerian princesses, there is evidence for their sacking of the great Sumerian city of Ur in about 1950 b.c.e. During the second millennium b.c.e. they swung between war and peace with the other Mesopotamian peoples to the north and west of them.
The Elamites first met the Persians as the Persians migrated south; even though the Persians were to have the upper hand it is clear that they adopted many things from the more sophisticated Elamite culture.
A good example of this cultural absorption can be seen in the sculptured reliefs of Persepolis (the high plateau royal capital of the Persian Empire) in which the Persians are wearing Elamite dress and carrying Elamite objects.
The Elamites generally acted as a go-between nation between the Mesopotamian peoples and the Iranian and other peoples of the high plateau. However, this role was not always an easy one; when the Assyrian empire was seeking to maintain its dominance in the seventh century b.c.e., Elam found itself at odds with the Assyrian king Ashurbanipal, who launched a series of campaigns against Elam that utterly destroyed the Elamite capital, Susa.
After the absorption of Elam into the Persian Empire in the sixth century b.c.e. the Elamite people began to lose their distinctiveness, even as Susa, their capital, became the main seat of government for the empire.
Neither the Medes nor the Elamites are separate peoples today. The Persians however maintain an identity as the dominant people of Iran. Iran changed its name from Persia in the 20th century to reflect the diversity of its people.