The total number of human annotations has remained unchanged since 2005, with 19 functional protein-coding genes [19]. The chimpanzee and the orangutan genomes diverged from humans ~5 and ~14 million years ago (MYA), respectively [20,21]. Both the chimpanzee and orangutan genomes contain 18 ALDH genes, each corresponding to a known human orthologue. The macaque and common marmoset genomes are more distantly related. They diverged ~25 and 35-40 MYA [22] and contain 20 and 16 ALDH members, respectively. Orthologues for all 19 human genes were identified in mouse and rat. In addition, rodent genomes contain an Aldh1a1 paralogue (Aldh1a7) and an Aldh3b2 gene duplication, resulting in a total of 21 Aldh genes. The most recent common ancestor of humans and rodents lived 75-90 MYA.
