Diet and human evolution: diversity of bitter taste genes and malaria in central-western Africa
From the appearance of our genus, which occurred about 2.7 million years ago with Homo habilis, up to much of the history of Homo sapiens, human groups have based their subsistence economy on scavenging or hunting for animal prey and gathering vegetables. With the Neolithic transition, this food supply model was replaced by systems based on agriculture and livestock. However, even today some human groups rely exclusively or mainly on food resources already available in nature. In this regard, central-western Africa is an area of considerable interest as it is home to human groups that adopt both of these lifestyles. Among these are the Pygmies, semi-nomadic populations living in forest environments, and the Bantu, a linguistic grouping that includes over 400 ethnic groups widely spread in sub-Saharan Africa.
Given the continuous deforestation of sub-Saharan Africa, mainly due to the intensive use for agricultural purposes by the Bantu, particularly favorable environments have been created and expanded for the spread of vectors (genus Anopheles) of Plasmodium falciparum, responsible for the so-called malignant tertian.
In both Pygmies and Bantu there are genetic variants that confer protection against P. falciparum malaria, which mainly concern hemoglobin and erythrocyte enzymes and antigens. Another important study perspective is the role of eating habits. In particular, it is known that some bitter-tasting compounds introduced with the diet can exert a protective action against malaria; the greater or lesser perception of this taste could be decisive for their continuous intake and for a possible protective effect. The perception of bitter taste is determined by a family of TAS2R genes (Taste 2 Receptors), 25 in total, which code for specific receptors, with different substrates, and divided according to affinity with certain compounds (binders). Several studies have made it possible to identify two phenotypes, the ancestral one (not taster) and the derived one (taster). The latter would have been favored by natural selection as it would have made it possible to avoid particularly harmful compounds, with a distinctly bitter taste.
The project, supported in part by the Italian Institute of Anthropology, aims to investigate the possible role of the perception of bitter taste in protection from malaria, through the analysis of the diversity of all taste genes known to date in a total of you are Bantu and Pygmies of central Africa. These populations lend themselves very well to this study as their traditional diet includes foods such as cassava, palm nuts, fruit seeds, wild or cultivated herbs and vegetables that contain bitter compounds with possible anti-malarial action.