Oxytocin and vasopressin are ancient, highly conserved peptides consisting of nine amino acids that differ by only two amino acids.

“okay so they're these small little peptide they're nine amino acids long are very tiny they only differ by two amino acids and they're these ancient peptides that are hundreds of millions of years old and in almost any species studied um whether it's the current version you might have vasit tocin or other Mosin which are um sort of precursor forms in other species but they're highly evolutionarily conserved”