As noted at Ouroboros, there's still plenty to debate in calorie restriction science. Well-funded companies are developing therapies and human studies have been taking place for years, but discussions continue on the basic research in lesser species: "In the last decade, research into the molecular determinants of aging has progressed rapidly and much of this progress can be attributed to studies in invertebrate eukaryotic model organisms. Of these, single-celled yeast is the least complicated and most amenable to genetic and molecular manipulations. ... Activation of Sir2-family proteins in response to calorie restriction (CR) has been proposed as an evolutionarily conserved mechanism for life span extension. This idea has been called into question with the discovery that Sir2-family proteins are not required for life span extension from CR in yeast. ... Several specific cases where the Sir2 model of CR is inconsistent with experimental data are noted. These shortcomings must be considered along with evidence supporting a role for Sir2 in CR in order to fully evaluate the validity of this model." A number of other possible candidate genes and proteins have been put forward in the past year; as scientists continue to investigate, the situation will become more clear.