Babies laugh, monkeys laugh.

How fun would this research project have been? Researchers elicited laughter (tickle-induced vocalizations) from infant and juvenile orangutans, gorillas, chimpanzees, and bonobos and babies to explore the emergence of laughter in primates. The results are reported in an article in Current Biology (available through Science Direct also). They analyzed the laughter and generated a cladastic family tree of the evolution of laughter which closely parallels the family tree generated from the genetics of these species.

Figure 3. Reconstructed Trees of Apes and Humans with the Siamang as the Outgroup Derived with Tickling-Induced Vocalizations

(A) The single maximum-parsimony phylogram as a result of exhaustive search (treelength = 113, RI = 0.750). Shorter branches indicate fewer character state changes.

(B) Bootstrap cladogram as a consensus tree of 10,000 replicates. Bootstrap values for ingroup clades are shown just above their preceding branches.

How did they come up with the idea and what implications does this have for laughter as communication and its evolution?