It seems that we all were licking paper dipped in phenylthiocarbamide, or PTC, which is a bitter organic compound. PTC does not occur in food, but people who can taste PTC are supersensitive to bitter compounds in foods such as broccoli and Brussels sprouts. Stone brought the PTC to Chicago to show how humans vary in their ability to taste different foods.
Where did this sensitivity come from?
But when Stone sequenced variants of the gene in humans and chimpanzees, she found that they had inherited different variants of the gene--in other words, the ability to detect bitter fruit had evolved independently in both species. This genetic adaptation may have spread among some human and chimpanzee populations because "there are natural occurring bitter compounds that should be avoided for potential toxicity," such as quinine found in bark, says biologist Claude-Marcel Hladik of the Muséum National d'Histoire Naturelle in Paris.
At the meeting, Hladik also reviewed his own landmark studies that found that humans vary in their ability to taste sugar and salt--differences that arose as modern humans spread out around the globe in the past 100,000 years and ate different foods. In particular, Hladik noted that the Inuit of Greenland are far more sensitive to salt than most other humans, perhaps because they have to drink large amounts of fresh water to wash out the urea that accumulates in their blood from eating a diet rich in seal meat and fat. If the Inuit could detect small amounts of salt in the first sip of water melted from sea ice, that would protect them from consuming water polluted with salt and from getting sick. So, the genetics of dietary adaptations explain why it would be unkind to salt the food of an Inuit--or to pass the Brussels sprouts to Ungar.