In which tribal societies do children abandon or kill their parents? It happens mainly under two conditions. One is in nomadic, hunter-gather societies that often shift camp and that are physically incapable of transporting old people who can't walk when the able-bodied younger people already have to carry their young children and all their physical possessions. The other condition is in societies living in marginal or fluctuating environments, such as the Arctic or deserts, where there are periodic food shortages, and occasionally there just isn't enough food to keep everyone alive.