translation.en: 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.
translation.zh: 另一种是生活在极端恶劣 或极端不稳定环境中的部落， 比如北极或沙漠， 这些地方有周期性的粮食短缺， 并且时不时的会有饥荒， 粮食无法满足所有人。