The most comprehensive study of the family tree for legumes, the plant family that includes beans, soybeans, peanuts, and many other economically important crop plants, reveals a history of whole-genome duplications. The study also helps to uncover the evolution of genes involved in nitrogen fixation -- a key trait likely important in the evolutionary spread and diversification of legumes and vital for their use as "green manure" in agriculture. To reconstruct the family tree, researchers compared the DNA sequence of more than 1500 genes from 463 different legume species, including 391 newly sequenced species, that span the diversity of this large plant family.