The answer is oropharynx.
The reason for this type of epithelium in this region of the respiratory tract is due to
its proximity to the esophagus. This
means that this region of the respiratory
tract is subject to abrasion by food
passing down the esophagus. This
epithelium is continuous with that of the esophagus.
The human race may survive through survival of the fittest. basically whoever has the biggest stick wins! The body also could adapt to the lack of water so you could preserve your bodily resources and manage them better. Or you could just change the environment to benefit yourself and mankind!