Behind the Thumb: Smack Dab in the Imagination by Dia Calhoun

 I've read that what made human beings leap ahead, and distinguished us from other species, was our opposable thumbs and tool making. This is a chicken and the egg problem--which came first? I want to know how imagination and the thumb/hand developed in relationship to each other--what drove what? And even in posing the question that way, I hear my left brain leading. My right brain says wait, no, this relationship between the hand and imagination was a dance where sometimes one led and sometimes the other. 

Anyone who creates anything knows this is how the best work is done.