that sounds kinda like the Host...haha
Yeah, I thought The Host had a bit more believable way of going about it--infesting through an incision in the back of the neck, and controlling the brain through very thin filaments projected along the nerves or whatever it was.
What Chad28 said is pretty spot on, about the method of controlling being something of a plot hole. In addition, even if there were a direct path from the ear canal to the brain, I'm hard pressed to come up with an explanation of how a Yeerk could fit inside the skull. It's not like we have Yeerk-sized air bubbles inside our heads---all the available space is already taken up by the brain and cerebrospinal fluid. Your skull can't stretch either, so shoving something as big as a Yeerk in there would cause your brain to compress = massive hemorrhaging, apocalyptic strokes and death.
Biology nerds yay!
I thought about this too when I took anatomy...there is just no way a Yeerk could get through the skull to the brain, not unless it went directly through bone...although I wonder if the auditory nerve canal might be another path? And all that description about shuffling ear bones around in
Visser...nope. Just not good for the host, not good at all. On top of that, yeah, there isn't a lot of space for a Yeerk to fit under the cranial dome, beneath the pia and dura mater layers of cranial membrane, and through the cerebrospinal fluid. I think it's pretty safe to say that a host would die
But who knows, maybe the Yeerks can slowly make their way into the brain, and instantly spread themselves so paper thin that it's not much different from having a layer of plaque on your brain (ew?), like in Alzheimer's? But then infestation would probably take hours, not minutes!
In Stargate SG-1 the goa'uld infest through the back of the mouth or the back of the neck, which is sort of more believable too, but then again they have giant snake bodies with VERTEBRAE XD so it just sounds silly, too.
The Puppet Masters by Robert Heinlein had slugs on people's backs, too...Joss Whedon, stop stealing! XD