Phylogenetic sequence analysis of IL4 from mammalian lineages. Shown is a neighbor-joining tree based on a nucleotide alignment (Additional File 3) of IL4 from the 28 eutherian mammals. The presented PhyML maximum likelihood phylogeny (using the HKY85 model) is rooted using elephant IL4. Numbers at branching nodes indicate the bootstrap support for that branch (1 = 100%). The orders of eutherian mammals are also indicated in bold with the Afrotheria (elephant) branch shown as the basally separating branch among the Eutheria .