Great Apes

There is little doubt that the basic, organismal laughter is a response to fear. The line of apes that gave rise to Homo seem to have a quite complex geographical history which included times when their environment was warm and supported large constrictor snakes. I believe the basic response to being caught by a CS (rapid breathing) has survived in the chimp, the the ancestors of which were the second great ape to migrate south, following the gorilla's ancestor.    

The ape that gave rise to one group of Homos (having dispersed throughout Eurasia) probably spent some time in a northern temperate environment, and then in the southern grasslands of Europe, now free of the threat of large snake attacks. This is probably when the basic laughter response became voiced and acted as a false alarm signal and also as a bonding play activity.

"There is a theory, one to which I subscribe, that the extant great apes began their evolution in Europe. There are very few fossil remains of great apes in Africa - only a few teeth which are thought to represent a species of gorilla and a species chimpanzee - but during the Miocene epoch (23.3-5.2 Ma) there were a large number of apes in Eurasia. A cooling climate may have caused the early European members of the great ape family (Hominidae) to migrate south into the warmer climes of Africa.   

 Humans differ from other apes in having a fat layer just below the skin and can conserve heat through a countercurrent blood flow system in their extremities. Other than the aquatic ape theory, there is no explanation why such adaptations should have evolved in Africa. This leads to the possibility that the ape that gave rise to humans was the last to enter Africa after existing alone for some time in temperate conditions. Further pieces of evidence that point to an "into Africa" scenario is the fact that a fossil ape from Hungary, Rudapithecus, has large frontal sinuses (absent in Asian orangutans), brow ridges and a downwardly bent face, typical of extant African apes.                                                                                                                                   

 The idea that laughter is an expression of positive valence ignores the fact that the most primitive form of laughter is exhibited during tickling. It is primitive in that it is found in our ape relatives and is also a reflexive response. Reflex responses are not under conscious control and are usually associated with survival behaviours. This means that the response of our ape ancestors to being touched in a certain manner (similar to tickling) was extremely rapid and independent of the other senses and cognitive inputs that might have slowed down escape strategies. Such split second, reflex responses would have been of great survival value during ambush attacks and night time attacks by tree climbing predators.                                                                                                                            
 The laughter patterns of humans and chimpanzees are the most rhythmic and have the shortest inter-call intervals of all the great ape species. However, whereas human laughter is voiced, chimpanzee laughter takes on the form of rapid panting. Why was the rapid panting of chimpanzees, and presumably the common ancestor of chimpanzees and humans, so important that it had to be encoded in their DNA?                                                                                                                               

Primates have a very long history of snake predation. This is inferred from the facts that monkeys have a specific alarm call for snakes and experiments have demonstrated a genetically based fear of snakes in monkey species. In 2011, German and Czechoslovakian researchers, working in Southern Germany, found 15 million year old fossilized snake vertebrae, which they calculated to be from a three and a half metre python. It is hardly likely they chanced upon the largest specimen of the largest constrictor species that existed in Europe at that time, and this find indicates the possibility of the existence of constrictor snakes capable of swallowing a medium sized primate. Constrictor snakes tighten their coils every time the prey animal breathes in, and it is possible that rapid panting disrupted this constriction process enough to allow the prey animal to wriggle  free.  

During the late Miocene cooling of Europe, large constrictor snakes either died out or migrated to warmer climates, and in some areas savannah-like grassland developed. This left our hominin ancestor with a stereotypic behaviour which I believe was vocalized and exapted to become an audible signal during play behaviour and also took on a mediating and communicative function in fight or flight situations.  "