The Economist writes about researchers who traced back the age of genes involved in genetic diseases, finding that they are older than had been suspected. The researchers, from the Max-Planck Institute for Evolutionary Biology, compared the genomes of disparate organisms to determine the ages of genes they had in common. In their paper in Molecular Biology and Evolution, they say that disease-causing genes are present in single-celled organisms and that mammal-specific genes contained few disease-causing genes.