if you DNA doesn't change with age, then how does the morphing technology determine which age the animal is in when you morph it?
I always assumed it to be the age that you aquire that animal.
Ex: when Ax morphs human, he aquires the Animorphs DNA at roughly age 13-14, give or take the serveral months considering when they all started the war, the months between that start n Ax's arrival n the gaps between all of they're b-days. Anyways, Ax's morph would be whatever that average age is. So towards the end of the war, Ax's human morph would be roughly 2 years behind the Animorphs' actual age. Same thing w Tobias after the Ellimist intervenes. His morph to his human self would be whatever the age was the night before they met Elfangor.