The real separation (and is something that comes long after 2 years of age in humans) is the ability to observe one's thoughts. I totally get that dolphins and elephants and many "big brain" mammals can have social structures, long memories, and the ability to pass down behaviors directly (e.g. "here's how you hunt fish effectively" may not be in dolphin genes, but they do a damn good job of it, or also the "fads" of orcas like the "salmon hat" or, more recently, attacking sailboats).

The absolutely blistering pace a child can learn at, though, is indeed quite a sight to behold.