http://www.pnas.org/content/104/47/18854.long http://www.pnas.org/content/104/47/18854.long and the talk about it: http://www.ted.com/talks/frans_de_waal_do_a

http://www.pnas.org/content/104/47/18854.long http://www.pnas.org/content/104/47/18854.long and the talk about it: http://www.ted.com/talks/frans_de_waal_do_animals_have_morals.html http://www.ted.com/talks/frans_de_waal_do_animals_have_moral...