I can't help but ponder over this fall out from the observation, that the more iodine a mammal species has access to in its diet (e.g. via aquatic foods), the larger the brain it can seemingly potentially evolve.
But why? Why iodine? And why only mammals? Aquatic birds don't develop large brains, aquatic reptiles don't, fish sure don't. Some molluscs like squid aparently can have large brains as well, is that linked to iodine as well?