In a frog, the position of the heart is determined within the first hour in the womb, Harvard scientists have discovered. Researchers all over the world believe that frogs and humans develop in a similar way. Experiments show, for example, that some of the same mechanisms put the hearts of both creatures on the left side. The proteins responsible for shifting around a frog embryo’s heart, gut, gall bladder, and other organs are also found in abundance in human embryos. “Our research shows the same protein family, known as 14-3-3, plays important roles across the three kingdoms of living things, fungi, plants, and animals,” says Michael Levin, a biologist at the Harvard School of Dental Medicine and the Forsyth Institute in Boston. “Our latest findings provide strong evidence that the determination of right-left asymmetry in vertebrates, possibly including humans, occurs at a much earlier time than previously believed.” Levin and two colleagues from the Netherlands described their newest experiments in the Oct. 20, 2003 issue of the journal Development.