[drekk]

Mice do have pretty complex multisyllabic vocalizations, it's just that the majority fall outside of our auditory range. It's the same for rabbits. They've even found that mice sing in different contexts (some courtship related, some not) https://www.frontiersin.org/articles/10.3389/fnbeh.2015.0007...

In humans at least we know that if an individual doesn't pick up a language as a child they will not be fully able to as an adult, and will have cognitive disabilities as a result. A modern example we had to read about in my neuroscience undergraduate program was Genie. When rescued from an abusive upbringing she was able to learn some nonverbal communication over the span of months, but missing that critical development period in childhood had lifelong impacts. https://en.wikipedia.org/wiki/Genie_(feral_child)

[lusus_naturae]

That's fair, and interesting. I don't think it takes away from the fact that cognitive flexibility is still the overarching emergent property that enables this.