morty not understanding summer's biology book makes sense because he felt the evolution process as part of himself—his own psyque. he is still a kid who feels things very deeply, unlike rick who goes for facts over feelings
rick’s and morty’s evolutions highlight their character’s core idea: rick, going ALONE in a path of blood to finish his goals to not “taint” morty; and morty, being dependent on rick or ANY adult and when left alone he blooms to his full potential, helping himself and others
I haven't seen anyone mention this yet so… Rick transformed from a ape back into a human after reuniting with Morty. It implies that Morty brought out Rick's humanity. Oh my little sweet boy❤️