Excellent topic that prompted a late reply from me.

Yes no matter who we are, all people have descended from those who once lived in a primitive tribe. Even the people who were the first Latin Romans came from tribes.

As far as what you said about peaceful tribes being conquered by other more powerful groups, this has been going on since sapiens swept the Neanderthal people away in what is now Europe. As far as peaceful tribes being conquered by the Romans, I’m prone to believe that most of these tribes had warriors and a history of conflict long before the republic and empire. The people who made the transition from independent to Roman subjects were of civilized nations themselves, like the Greeks and those in Palestine. The Celts, Teutons, Parthians and others were more of a warlike nature often subjugating others. Although enjoying early success against the Romans, their style of ‘warrior on warrior’ fighting could not stand up to the well trained legions of Caesar. The Parthians however destroyed a Roman army of thirty thousand and were never fully conquered. It was the spread of Roman Christian religion that survived empire and turned barbarian chieftains into the early Christian kings of Europe's dark ages. That was the death knell for the remaining tribal people of Europe. Conquest, inquisitions, forced conversions pretty much wiped out any large groups of remaining Pagan tribal people.

The eastern tribes were the first to clash with Europeans, fighting them for a few hundred years.

The tribes living in what is now eastern America lived close to nature, but they were in no ways peaceful as many of them had warrior societies. At one time they almost achieved an ancient civilization in the east complete with huge metropolitan centers like Cahokia and poverty point, but such large cities depleted the soil with their large scale agriculture. Game was also hunted out in these areas prompting large parties of hunters to travel into hostile territories of more primitive tribes whom these Mississippians were ever at war with, raiding for foodstuffs and slaves. A combinations of what I mentioned eventually brought down most of the Mississippian mound building culture.

These primitive tribes did not fight like Europeans of the time. The object was not to conquer or exterminate another tribe as there would be no one to raid, next season. A lot of ritual took place before the raid, often in the form of a war dance. Like in the movies, some preferred to attack at dawn thus having the advantage of surprise. Some of the southeastern tribes would even gain honors for killing women and children as they had to get by the enemy warriors to do so. Captives were taken though, to serve as slave like labor and sometimes adopted. Often male captives died a horrible long death at the hands of torturers. A warrior expected as much and often would attempt to go down fighting instead of dying a slow torturous death. Sometimes adult male captives were adopted to make up for a slain son, brother or husband in an enemy family.

When the Europeans came these tribes were decimated by conquest and disease. The ones who didn’t, got caught up fighting on different sides of European rivals and were eventually defeated and exiled during America’s Manifest Destiny.