Phagocytosis is to eating as pinocytosis is to drinking.
Answer: Pollution, climate change, habitat loss, or invasive species
Europe is the most likely answer.
Water had the capability to hold up the thin overhang of the underground.
When water is depleted, there is nothing to support this overhang, which eventually led to the formation of sinkholes.
As for the collective behavior, it's all because of the scarcity. Water is one of human's basic needs to survive. When water is scarce, this will force the people to compete with one another to obtain it, which will cause the behavior
