Thanks for bringing this up, I just thought of an interesting idea that I might use in my fic later on...
Glad to contribute,
Phoenix004!
I kinda derailed the topic doing that, sorry. The substance exists in the Animorphs universe, just like the Yeerk aliens exist, so that's that.
It's interesting to imagine that their bodies get all their nutrients from the pool and the Kandrona rays. The oatmeal could just be something that binds them to the hosts' brain.
My point is, the Yeerks have a completely unknown physiology. They may resemble snails, but are nothing like one. They may not have a brain, like we imagine a brain to be.
Does this make them smarter or more adaptable than humans? Nope, I dare say. A human has capacity to mimick, design and create new things. But a Yeerk simply steals it through memories not their own.
Suspend the host bodies, take the Yeerks out of the hosts and put them back in their natural state. Think of the body of a Yeerk. WTH would it need to design a pen, or wheel in a bike, or door to a room...??
I just think their creations would be somewhat 'limited' in comparison to humans.