clipped from: 
No less a personage than Charles Darwin looked into it
Nodding and head-shaking turned out to be pretty common, but there were some striking exceptions. For example, certain Australian natives, when uttering a negative, "don't shake the head, but holding up the right hand, shake it by turning it half round and back again two or three times."
Abyssinians said "no" by jerking the head to the right shoulder and making a slight cluck, while "yes" was expressed by the head being thrown backwards and the eyebrows raised for an instant.
The Dyaks of Borneo supposedly raised their eyebrows for "yes" and slightly contracted them, "together with a peculiar look of the eyes," for "no." Eskimoes nodded for "yes" and winked for "no."
where they completely reverse the meaning of our nod and head-shake gestures is Bulgaria. There a nod means no and a shake means yes.
One shudders to think of the implications this has for cross-cultural dating in that country.
