Michael Barker will never look at a Christmas tree the same way again. By thoroughly analyzing the genomes of spruces, pines, firs, and their relatives, he has uncovered that these trees underwent a genomic hiccup in their deep past. The result: They once had a complete second set of genes, the genomicist at the University of Arizona in Tucson and colleagues report today. Such a genome-wide duplication likely helped shape these species into the tallest, hardiest plants in the world and are causing biologists to rewrite the history of gymnosperms, the group of plants that includes conifers and other nonflowering, seed-producing plants.