We the people have been developing plumbing systems for a long, long time. And we probably should have started even sooner. The back of the cave must have been a right mess, after a long hard winter, one would expect. But what could we do without plumbing and plumbers?
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Archaeological excavations of some of the ancient civilizations of the Indus Valley have revealed that sanitary sewers were in place and quite sophisticated, considering the materials and tools at hand. Those early civilizers often had a sort of septic tank under the house, with broken pottery used to form a drain field of sorts. The toilet not being invented yet, access to the system was by way of a hole in the floor. But that is progress, at least. We have continued our efforts toward successful sanitation over the ages. And now we have the plumbing we need, and plumbers to keep it working for us.