Limestone caves and Tums...hum...what do they have in common? Growing up in Kentucky, there were certainly a number of limestone caves to learn from.
My first experience with total darkness was given in Mammoth Cave some 105 feet under ground. The lights were turned off, and suddenly there was darkness... darkness like no other. I even poked myself in the eye trying to see my fingers in front of my face. Wow, darkness like I had ever seen before. [Or not seen in before.] How could someone live in this sort of environment?
Limestone caves were indeed one of the earliest environments that human life experienced. The darkness was broken when that fire came under control. It must have seemed pretty bright at the time since I remember seeing a cigarette glowing in the darkness of Mammoth Cave that day... a flood light in the blackness.
Water and limestone must have been part of the secret. Being a sedimentary rock, it is composed of 95% calcium carbonate. Water, melting and freezing, would leave its trail along the way. Lime water would result, and would give a source of water in a milky looking aqueous solution. You could soak hides and skins in this "milk of lime" causing them to swell. This would help the removal of hair and such from these skins making a much better style of cloths. Lime putty could be made and ultimately lime mortar [ a mixture of hydrated lime, sand, and water]. You could then start putting things together.
In Wales, human existence started in these limestone caves. Certainly after eating all that meat to get to those skins, you would have to digest a great deal of things. The diet must have been pretty rough. When that late night "heart burn" would start, you would only have to take a little extra sip of that lime water [calcium carbonate], the Tums of our day! Seems like very little has changed.
"Tums" Ultra Strength 1000 = Calcium carbonate USP 1000mg...Antacid!