by Roger Bourke White Jr., copyright August 2005
Ah ... pop the top ... it fizzes. Take a swallow ... ice cold! What can beat the refreshing feeling of a cold pop on a hot day!
But why do humans find a cold pop refreshing? There are, perhaps, good evolutionary reasons why humans like cold, carbonated, sugary beverages. There may be a human instinct behind this joy. This essay is a speculation on why evolution may have developed an instinct in mankind to enjoy cold, carbonated water.
Water is necessary for life, all kinds of life. Humans need and love water, but so do plants, other animals, fungi, bacteria, and viruses, and some of these are harmful to humans (pathogens).
Water that has been in a sun-warmed puddle for a few days or has been at the edge of a shallow lake during growing season is one of the easiest places for life to thrive. As a result, it is an environment of fierce competition among many life forms. It is filled with all sorts of living things, and a few of those things are either poisonous to people or really good at living inside people. This makes warm, muddy, smelly, stagnant water very risky for people to drink, and it has been so for millions of years -- long enough for people to develop an instinct not to drink it.
On the other hand, water that has been lying deep in the earth is relatively sterile. It's been cold and dark, probably for a long time, and filtered by rocks. Whatever was living in the water as it sank deep into the rocks is long dead and left behind. When this kind of water comes to the surface again, it is called spring water. Not only is it cool, it has often absorbed some gas -- carbon dioxide gas -- while it was in the ground, so it comes up with a CO2 tang, as well.
This is spring water, and it has low risk of carrying dangerous pathogens. Spring water has been around for millions of years, too, so it’s likely that humans and other animals have evolved an instinct to feel that spring water is favorable to drink.
If a little cool and a little fizzy is good, is not a lot of cool and a lot of fizzy even better? Instincts are often not precise, so if an instinct suggests a little of something is good, then that same instinct is likely to suggest a lot is better. A peacock's brilliant plumage is one example of this, and another is cartoon imagery of handsome men and beautiful women.
Soft drinks may be another example: A little cool is good, so a lot cool is better; a little CO2 in the taste is good, so a lot is better. Add some nutritious sugar and flavors and ... voila! We have a modern, thirst-quenching soft drink.