“I hear you. If it was an epidemic there’d be a lot more children than adults.”
Unless it was like the Spanish Flu.
Within the context of human society, it seems more likely to me that a stronger force raided the village for slaves, and left behind the corpses of adult and near-adult males.
Still just guessing, though.
My take on the body heap...
The youngsters developed an early form of rap music and the oldsters decided to get ahead of the cultural rot with a bit of old school eliminationism.