An evolutionary perspective on food and human taste

Abstract

The sense of taste is stimulated when nutrients or other chemical compounds activate specialized receptor cells within the oral cavity. Taste helps us decide what to eat and influences how efficiently we digest these foods. Human taste abilities have been shaped, in large part, by the ecological niches our evolutionary ancestors occupied and by the nutrients they sought. Early hominoids sought nutrition within a closed tropical forest environment, probably eating mostly fruit and leaves, and early hominids left this environment for the savannah and greatly expanded their dietary repertoire. They would have used their sense of taste to identify nutritious food items. The risks of making poor food selections when foraging not only entail wasted energy and metabolic harm from eating foods of low nutrient and energy content, but also the harmful and potentially lethal ingestion of toxins. The learned consequences of ingested foods may subsequently guide our future food choices. The evolved taste abilities of humans are still useful for the one billion humans living with very low food security by helping them identify nutrients. But for those who have easy access to tasty, energy-dense foods our sensitivities for sugary, salty and fatty foods have also helped cause over nutrition-related diseases, such as obesity and diabetes.

Figure 1. Taste papillae and taste buds of the human tongue

The human tongue contains three types of taste papillae. Vallate and foliate papillae reside on the middle and sides of the posterior 1/3 of the tongue, respectively, and contain hundreds of taste buds collectively. Circumvallate papillae comprise an arc of small ring-like structures (tiny towers surrounded by motes) in posterior tongue. Foliate papillae are slits (leaves) in the side of posterior tongue and can appear like gills in the tongue. Fungiform papillae look like small bumps or mushrooms and are scattered in the anterior 2/3 of the tongue, each harboring 0–15 taste buds. Taste buds are also located in the soft palate (non-bony palate in front of the uvula) and pharynx (back of the throat) but are in the flat epithelium, rather than in papillae in these locations. The first inset depicts the microscopic taste buds residing within the epithelium (outer layer) of a fungiform papilla. The small structures surrounding the fungiform papilla are called filiform papillae, which do not contain taste buds, and serve to make the surface of the tongue rough and help detect food textures. The second inset depicts a single rosette-shaped taste bud from within this fungiform papilla that contains dozens of taste receptor cells and contacts taste stimuli within the oral cavity via a small epithelial hole called a taste pore.

Figure 2. The attributes of a taste percept

Each taste percept may be subdivided into multiple taste attributes that are integrated to form a single taste sensation.

Figure 3. Evolutionary dendrogram of apehominid evolution

The vertical axis represents time and ends in the present with gibbons, orangutans, gorillas, chimpanzees, and humans contemporaneously existing. The vertical distance from the top to a branch point along the dendrogram is the time to coalescence. Where ape lineages join represents when the two species shared a common ancestor. All modern apes live in closed tropical forests, and obtain all of their nutrition there. Their last common ancestor to the apes would presumably have lived in a similar environment. During early hominid evolution, human ancestors left the forest for the savannah and other ecosystems and their dietary repertoire greatly expanded. Eventually their diet is hypothesized to have included more meats, fermented foods, and, most recently, large amounts of starch due to the advent of agriculture.