Scientists from the National Institute of Dental and Craniofacial Research (NIDCR) and Howard Hughes Medicine Institute researchers at the University of California, San Diego, have identified a family of as many as 80 genes that perform the same function: to allow people to detect whether a substance has a bitter flavor. Each of the genes encodes a different taste receptor that allows humans to identify a wide range of bitter compounds.
Having such a large family of bitter-receptors makes evolutionary sense. Because bitter flavors in nature often signal that a substance is poisonous, being able to recognize a wide range of natural poisons has obvious survival value.
Stephenson J. Bitter Truth. JAMA. 2000;283(15):1950. doi:10.1001/jama.283.15.1950-JHA00002-3-1