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?