some would say we actually have sapient species, that have rudimentary languages. all ready but what is the true defining definition of humanities superior intelligence is our culture, or simply the fact that all ideas for our race, tirbe, or even family groups, build on each other, or the quote "Do not call me a genius for simply stand on the shoulders of giants.
I call this Meta-Sapience or the ability to not only think for yourself and its prospects but also to build upon past ideas using other info that you have access too.
This process is probably also why technology and information raises exponentially, and accounts for the "sudden" leaps humanity got in its ages.
and also why things like the dark ages really did set us back, as information or the ability to decipher it was either lost or destroyed.
This is the true boundary a sapient animal would have to cross to acquire huamniod like intelligence not only a language but the ability to codify it to pass information through predecessors.