The Wall Street Journal reports on another gene that regulates the benefits to health and longevity produced by calorie restriction: "This gene is absolutely essential for the response to dietary restriction [in] prolonging life span ... we're still in the identification [of genes] phase and a long way from clinical trials. ... The gene [known] as PHA-4 was discovered in worms, where it plays a key role in the embryonic development of the intestine. However, PHA-4 also coordinates other genes that influence how the adult worm's body responds to a restricted diet. Humans possess three genes that are very similar to PHA-4. ... The gene is highly conserved in humans, mice and worms. So its function in humans could be similar. ... Other researchers have studied a different gene, SIR-2, which plays a role in extending longevity of yeast, worms and flies. However, its role isn't as specific in influencing the calorie-restriction response as PHA-4." So continues the process of narrowing down the focus: how exactly is it that calorie restriction extends healthy life? When that question is answered, engineering similar benefits for everyone through medical science becomes a plausible goal - albeit not as efficient a way forward as other plausible goals.