NCG collects orthology information for 723 out of 736 cancer genes (98.2%), since 13 genes are not present in the eggNOG database. We find that 61% of cancer genes originated very early in evolution, because orthologs can be traced back either to LCA or to early Eukaryotes. As few as 2.5% of cancer genes appeared with Opisthokonts, 17.7% with Metazoans, 15% with Vertebrates and only the remaining 3.8% with Mammals and Primates. These results are consistent with previous reports, which assess that disease genes are overall depleted in recent genes (46).
