Ancestors of Hobbits
The Men who after the first rising of Sun were found by Avari Elves became their friends. But soon Morgoth's power came back to those regions, easternmost of Middle-earth, and made war to those who did not obey, so many Men and Elves fled to the West.
The noblest and most remarkable of those Men were the three tribes of the Edain who came to Beleriand and were allied to the Noldor in the War of the Jewels. But though those three houses grew and gave many heroes and originated, at last, the great people of the Dúnedain, they were but the vanguard of large movements to the West. Even there were some who, leaded by Bereg, came back from Beleriand, and rejoining their kin East of the Blue Mountains, became the Eriadorans.
Because of the contiguity of Eriador to Beleriand, almost all of those who had marched there had crossed the Blue Mountains, because the longed country was near, and the Eriadorans were few in comparison to the Gwathuirim (the primitive Dunlendings) and their kin, the ancestors of the Hillmen, who lived to the north.
That's why the majority of the Edainic Men were those who had stopped their journey in Rhovanion. In the First Age, the Sea of Helcar limited at the East those lands, and the biggest extension was still covered by the Great Greenwood, where lived the Silvan Elves, mixture of Nandor and the newcoming Avari.
So the Men of Rhovanion (the Northmen) dwelt the borders of the Wood, and the Anduin vale north of the Nandorin dominion of Celebrant (future Lórien), and the plains between the Wood and the Sea; when Helcar disappeared at the end of the Age, its remnant the Sea of Rhûn kept being the eastern limit of the Northmen because some Easterling penetrated rapidly the new plain.
The Men of Rhovanion, until then companions of Elves, found new allies at the beginning of the Second Age. Because from the destruction of Angband many of Morgoth's servants fled to the East and the South, and coming down the mountains they invaded Eriador and Rhovanion disturbing their inhabitants, were they Dwarves, Elves or Men.
Dwarves of different houses had their homes in many excavations in the Misty Mountains, and their fierce defence was overwhelmed by the only advantage that Orcs had at every time: their great number. The Orcs occupied the dwarvish homes in northern Hithaeglir, being the main of them Mount Gundabad.
Then Dwarves made an alliance with Men of both sides of the Mountains: Men were helped to build stone houses and defences; while they provided mounted archers (they had got horses from the Noldor in the First Age), who in many occasions dispersed great Orc groups before they could make their raids. The combined strength of Men and Dwarves in the North was as important as to drive back the servants of Morgoth from their recent conquests and confine them in the tundra of Forodwaith.
As the Gwathuirim of Enedwaith and Gondor, Men and Elves of Rhovanion lived their best time in the first half of the II millennium of the Second Age. For Sauron was already among the Noldor, and when he failed to subtly take control over them, he went forth to the conquest of the western lands.
If Eregion was ravaged and Lindon besieged, being both kingdoms of the powerful Noldor, destruction and death to the East were terrible, due to the advance and retreat of Sauron's armies. Of all Rhovanion only the inner parts of the Greenwood escaped the ruin.
The losses of Elves were terrible, but even more among Men, who lived in more open and unprotected lands. The Eriadorans, protected by Gil-galad and later by Númenóreans, did not suffer too much, but their relationships with their kin of Rhovanion ended.
Here, those who survived the annihilation, which was utter in the midst and south of the land, remained isolated and impoverished in some small peripheral communities: west of the Sea of Rhûn, or in the ravaged borders of the Wood, or in the southern slopes of the Grey Mountains.
Because of the special rage that the vengeful invaders called by Sauron from Forodwaith used with Dwarves and the Men who lived near them, only one diminished human community lasted between the Anduin and the Misty Mountains: those of small stature who remained isolated and were not mentioned in chronicles until several millennia passed.