Binghamton University scientists have posited the evolutionary origins of types of laughter -- stimulus-driven and that which is self-generated.
"Laughter that occurs during everyday social interaction in response to banal comments and humorless conversation is now being studied," write biologists Matthew Gervais and David Sloan Wilson. "The unstated issue is whether such laughter is similar in kind to laughter following from humor."
The scientists claim laughter originated from apes mimicking the panting of other apes during periods of play between 2 million and 4 million years ago.
However, neuropsychological and behavioral studies have shown laughter can be more than just a spontaneous response to stimuli. Around 2 million years ago, humans evolved the capacity for willful control over facial motor systems, co-opting laughter for a number of novel functions, they hypothize.
"Humans can now voluntarily access the laughter program and utilize it for their own ends, including smoothing conversational interaction, appeasing others, inducing favorable stances in them, or downright laughing at people that are not liked," write Gervais and Wilson.
Their research is detailed in the forthcoming Quarterly Review of Biology.
Copyright 2005 by United Press International
Explore further: NJIT mathematician's 2015 Major League Baseball projections