Fig. 1.

A: phylogenetic tree for relevant mammals, developed in TimeTree. Scale bar represents molecular time estimate. B–F: amino acid (AA) sequences from Weddell seal, aligned against dog. Conserved domains from dog are in boldface. AAs denoted in blue differ in seals compared with all other mammal sequences (dog, human, cow, sheep, rat, mouse) collected from NCBI Homologene but indicate a substitution with a physically similar AA. AAs denoted in red are also unique to seal but represent a significant substitution with an AA of altered charge or polarity compared with other mammals.