Phylogenetic relationsship between eukaryotic core histone types H3 and H4 as well as archaeal histones. A bootstrap consensus Neighbour Joining tree (A.) illustrates the phylogenetic relationsship between eukaryotic histones H3 and H4 as well as archaeal histones, which share common ancestry. More divergent H3 and H4 variants of kinetoplastids occur as sister groups with regard to their variants from other eukaryotes, probably due to long branch attraction. Similarly CenH3 variants occur as long branching sequences. The protein sequence alignment (B.) shows a conserved region from the histone fold domains of several eukaryotic histones H3 and H4 as well as archaeal histones. Residues identical in >95% of all sequences are shaded black. Residues similar in >95% of all sequences are shaded grey.