Spanish researchers say they're a step closer to resolving a mystery of evolution - why some people like Brussels sprouts but others hate them. They have found that a gene in modern humans that makes some people dislike a bitter chemical called phenylthiocarbamide, or PTC, was also present in Neanderthals hundreds of thousands of years ago. The scientists made the discovery after recovering and sequencing a fragment of the TAS2R38 gene taken from 48,000-year-old Neanderthal bones found at a site in El Sidron, in northern Spain.
     The findings appear in a report released by the Spanish National Research Council (CSIC) in the Royal Society journal Biology Letters. "This indicates that variation in bitter taste perception predates the divergence of the lineages leading to Neanderthals and modern humans," they say. Substances similar to PTC give a bitter taste to green vegetables such as Brussels sprouts, broccoli and cabbage as well as some fruits. But they are also present in some poisonous plants. So having a distaste for it makes evolutionary sense. "The sense of bitter taste protects us from ingesting toxic substances," the researchers say.
     What intrigued the researchers most is that Neanderthals also possessed a recessive variant of the TAS2R38 gene, which made some of them unable to taste PTC - an inability they share with around one third of modern humans. "These (bitter) compounds can be toxic if ingested in large quantities and it is therefore difficult to understand the evolutionary existence of individuals who cannot detect them." The report's lead author, Professor Carles Lalueza Fox of the University of Barcelona, speculates that such people may be "able to detect some other compound not yet identified." This would have given them some genetic advantage and explain the reason for the continuation of the variant gene.
     Excavations since 2000 at the site at El Sidron, in the Asturias region, have so far recovered the skeletal remains of at least 10 Neanderthal individuals.

Source: ABC Science (13 August 2009)