In almost all other species, especially primates, baring one's teeth is a threat or a show of potential force. Are there any cultures in which smiling is not considered friendly?
Cities try cooling off with deep lake water
Dying plants harvest harsh surprises from climate change
Controversy heats up about chlorfenapyr, a.k.a. Pirate--a pesticide some claim is the next DDT
Gorillas and the rain forest come to the Bronx