Yeast and roundworms are where the search for longevity-determining genes often begins, as demonstrated in this EurekAlert piece: "Howard Hughes Medical Institute researchers and their colleagues have now uncovered 10 new genes that regulate longevity in yeast. The studies also suggest a new model for how aging is slowed when caloric intake is restricted. ... We'd like to understand how aging occurs in yeast. Even though yeast is a simple, single-cell organism, it's still capable of revealing mechanisms in the aging process. Similar genes may control aging in higher organisms, too. ... The two years of laboratory work, much of it done by Kaeberlein and Kennedy, were extraordinarily tedious, involving complex genetic and biochemical tests on a special collection of 4,800 strains of yeast cells developed by other scientists."