Evolution of new characters after whole genome duplications: Insights from amphioxus

► Many vertebrate-specific characters (e.g. neural crest) evolved from structures present in invertebrate chordate ancestors. ► Whole genome duplications at the base of the vertebrates facilitated the evolution of vertebrate-specific characters. ► Comparisons with invertebrate chordates such as amphioxus give insights into the co-option of old genes for new roles. ► Evolution of new cis-regulatory elements after whole genome duplications has led to neo- and sub-functionalization of genes. ► Point mutations and changes in alternative splicing of proteins can result in gain of new functions after gene duplication.