I think actually, they were pre-Adena. The Adena brought with them some mound technology. My guess is that the old Indian folklore is correct, that there was a confederacy of what we now think of average-sized Indian peoples, who came together to "annihilate the abhorrent Ronnongwetowanca." I suspect there were a serious of battles in the war, that raged from west of the Mississippi on up the Ohio River Valley. The victors, mostly Adena, buried all the enemy in a series of mounds and fortress walls.
As the saying goes among some tribes, they attacked the enemy and "rubbed them out" (is the literal translation).
The link that I gave above, reminded me of reading up on the topic some time ago.
I became curious because there is a mound that is just three hundred yards from my front door. It is almost 50 ft in diameter and about twenty feet high.
"I became curious because there is a mound that is just three hundred yards from my front door. It is almost 50 ft in diameter and about twenty feet high." Can't say for sure what went on but, there are a lot of stories/myths...and, usually where there's smoke, there's fire. So...