Symbolic Communication: Why is Human Thought so Flexible?

Why is human thought so flexible? Although many features of human brains can be attributed to selection for novel cognitive functions (e.g., for symbolic language), relaxation of selection on other attributes has additionally contributed to de-differentiation of certain brain functions. A parallel process will be described involving domestication and birdsong. In humans, this has produced a reduction of innate behavioral tendencies, new possibilities for novel synergistic brain functions, and an offloading of functions onto socially transmitted information. It has also influenced human emotional systems in ways that have contributed to our aesthetic, empathetic, and even religious predispositions.