The tree follows what is generally accepted regarding species evolution and whole genome duplications. Cnidarian CREBBP/p300 contains the NCBD domain. Since these species are distantly related to the other animals in the tree Cnidarian CREBBP/p300 proteins are used as outgroup in the analysis. After the divergence of Cnidaria from other metazoans, deuterostomes and protostomes diverged from each other. The node between the deuterostomes and protostomes (marked with a dark blue circle) is the oldest time point that we resurrect. Protostomes contain groups such as insects and molluscs, while deuterostomes contain all vertebrates. At the beginning of vertebrate evolution two whole genome duplications occurred. Thus, at this point all vertebrate genes were duplicated twice resulting in four copies, but many were rapidly lost. For CREBBP/p300, two copies remained, namely CREBBP and p300. The node corresponding to the ancestral CREBBP/p300 protein is marked with a green circle and referred to as 1R/2R in the text, since we cannot distinguish these events for CREBBP/p300. The most recent node that we resurrect is the separation of Teleost fish CREBBP from Tetrapod CREBBP (marked with a light blue circle). A third round of whole genome duplications later occurred in the fish lineage (not indicated) resulting in the two variants CREBBP1 and CREBBP2. The indicated resurrected nodes correspond to the same nodes as in the simplified
Figure 2 in the main text.