Why do humans have a sense of taste? Like our other senses, the ability to taste adapted and evolved over millennia in response to environmental pressures. Just as humans developed keen eyesight to both spot predators and check out potential mates, our sense of taste serves two basic purposes: keeping us alive and healthy enough to reproduce.
The taste buds concentrated on our tongues are armed with fine-tuned taste receptor cells that connect, through nerve pathways, directly to the brainstem [source: Henney et al.]. When we pop something into our mouth, these receptor cells analyze the molecules in the food for five different taste categories: salty, sweet, sour, bitter and umami (savory).
When our ancient genetic ancestors roamed the forests and steppes searching for food, a sensitive palate could mean the difference between life and death. If the leaves of a plant taste were especially bitter, they could be poisonous. A salty taste could mean that the food contained important minerals and nutrients. And sweetness suggested the existence of glucose, the original brain food.
But our sense of taste goes way beyond the tongue. The flavors we sense from food are the combined result of several simultaneous and little understood processes. The odors of food, not necessarily their direct "taste," play a huge role in delivering flavor. (There's a trick where you hold your nose while eating a jelly bean. Chances are you won't be able to taste its flavor.) Those odors drift up the back of the throat into the nasal cavity where they light up a panel of smell detectors. How food tastes is also a learned experience that depends on what you ate as a child, or even what your mother snacked on when you were still in the womb [source: Beckman].
Flavor enhancers tinker with both the evolutionary and emotional components of taste. Sodium and glutamate, for example, are both critical to cellular function. We have to consume a baseline amount of these minerals and amino acids daily to survive, which partially explains why we have evolved to not only sense salty and savory flavors, but to find them delicious.
But why does the addition of these substances to other foods enhance or otherwise alter the way we experience them? Salt, for example, can not only make chocolate taste sweeter, but also somehow make canned soup taste "thicker." Scientists are just beginning to understand how salt suppresses the detection of bitter chemical compounds, therefore bringing out a food's natural sweetness or savory edge. As for "thick" soup, salt might also trigger "touch" neural systems that send mixed signals to the brain [source: Henney et al.].