You are wrong if you think that people are single from animals who can laugh.

check "laughing rooster" in youtube :D :D :D :D :D 

http://www.youtube.com/watch?v=3qamvbvLQXM

apes are ancestor of human being.

"Apes Giggle Like Humans"

<a href="http://www.youtube.com/watch?v=SnbKzDkZktQ">http://www.youtube.com/watch?v=SnbKzDkZktQ</a>;