Brains of the Animal Kingdom: Research shows we've underestimated 13 years ago
Yet don't you think your last statement there is a perfect example of walking through a quiet wood and declaring a woodpecker absent? We certainly don't understand non-human languages/communication systems, and significant evidence is piling up that it's often far more sophisticated than we think it is. And "building on previous generations' achievements" is a little ill-defined; isolated groups of individuals often form a unique society, even if they aren't conducting research on human intelligence.