> Of note is an abrupt excursion toward a wet climate between 4.3 and 4.0 ka B.P. followed by an abrupt dry event between 4.0 and 3.6 ka B.P., a wet period between 3.6 and 3.3 ka B.P., and another dry period between 3.3 and 3.0 ka B.P. (Fig. 3, E and F), which can be also observed in the Yangkou cave δ13C record (Fig. 3D) from the middle reaches of the YRV, indicating unstable climatic conditions between 4.3 and 3.0 ka B.P. in the region

That would be very frustrating having your ancestors complain of too much water and you’re living through a ‘mega drought’. Then repeated swings.