I actually have a different theory. We hear "DNA, DNA," but where did that come from? Elfangor's very hurried "how-to-use" explanation, to an alien species, whilst dealing with a species identity/loyalty crisis and his impending death.
If he told a small lie to children or oversimplified things, I think we can understand.
Any biologist knows that development is not strictly determined by genotype. Heck, anyone who knows "identical" twins knows this. Or, think about how morphing (unlike cloning) reproduces age and physical attributes like fitness or even hair length.
Cerbral palsy is a good example because it is not heritable and has absolutely nothing to do with DNA. It's caused by brain injury, especially to very young brains. No other known cause.
Remember when (IIRC) Rachel experimented with adjusting her hair length by morphing?
And then, there's that rule about only morphing animals. They break it by morphing alien species far, far more genetically distant than a rose or paramecium.
Well, here's my crazy theory:
It all has to to with
identity, particularly some metaphysical sense of what is the "right" way for the physical matter of your body to fit together.
You morph a bear and loose a limb. You don't accept that (on a subconscious level) as the "real you" or even as the "bear you." Morphing fixes it.
You've lived with CP all your life. You've grown to accept it as you, just as much as your fingerprints or iris patterns in a deep, and apparently somehow physical level. Morphing won't "fix" you, because
you're not broken.
You return to your true form by remembering what it is and
willing to return to it. You must touch base on this form before borrowing another.
You wear the scars the world inflicts upon you with a sort of twisted pride, so when your cat gives you a well-deserved scratch for playing strange alien make-believe, you accept that too. Morphing doesn't fix it because
you're not broken.
(KASU? No, K A Is Brilliant!)
You can morph a dog or kafit because (subconsciously) a dog or kafit knows what it is. But, you can't morph a tree because a tree
doesn't.
A borrowed self is, well, stolen. Morphers are
identity plagiarists--they copy not only DNA, but body and conditioning and, ooh, get this: learned behaviors. Flight in birds is not instinctive. It's learned, through trial and error and a lot of good luck. Unless you morph something really bizarre like a Howler, you don't get declarative/narrative memories.
I think this might be more a privacy/comfort feature than a core limitation of the technology. Body, instincts, training, those are enough to deal with without adding memories or social identity to the mix. Andalites are already shocked enough with morphing as it is--they're comfortable with a social structure that defines who they are and what they should do. Something that
changes who you are is very disturbing and they're surprisingly and infuriatingly averse to the technology.
Unlike humans. We're very flighty and imaginative, the sort of species that actually thinks it'd be cool to be a bird for an hour or two or maybe forever.
So, morphing copies "self," but not perfectly. The copy is a "self-with-amnesia" (amnesia fogs autobiographical memories and facts, but not language or "muscle memory" skills or intuition) and a convincing story about where that self came from. "You are a temporary self. Really, deep inside, you're something else. You have two hours to change back."
This leads to an interesting and shocking problem. Does the archbishop dream he's the grasshopper, or the grasshopper dream he was an archbishop?
The very dangerous truth about morphing is that when a kid fighting an alien invasion becomes a tiger, he
really becomes a tiger. A very strange tiger that's forgotten that it's a tiger and has been bamboozled into thinking that it really is a kid fighting an alien invasion and thus does very un-tiger-like things, like attacking a walking salad shooter instead of finding something smaller and unsuspecting to kill and eat. How long can that lie hold together?
Maybe a little longer than two hours. After that, he's a tiger
by choice--and that choice is beyond the power of the Escafil device to reverse. He's called a "nothlit" a nonsense word that stands for a concept in Andalite thought without an English equivalent, but which very well might be related to this:
[spoiler]
[/spoiler]
Oh, and this idea of "self" as in "a metaphysical something of what an organism
should be that drives it
to be" is not something I came up with entirely by myself. It's strikingly similar to a concept in Scholastic philosophy that goes by the Latin term
anima, related to the English "animate" and (conveniently) "animal." It's usually translated to a different Anglo-Saxon word. We might say that then morphing plagiarizes the
soul...
...and it's official. I need to go to bed now.
So, to try and bring this digression back on topic, I think the inconsistencies and incongruities of "therapeutic morphing" open up one
hell of a can of worms related to the question of "yes, a return to health, but what
is health anyway?"