The excellent book The biology of Religious Behavior edited by Jay R Feierman provides an excellent framework on how to understand the biology and evolution of religion.
Viewed from a neurodiversity-perspective, there are certain troublesome aspects of religious behaviors:
- Shamanism and delusions seems to be related to neurodiversity
- Prosocial behaviors, submission and cooperative behaviors seems to be neurotypical
The Neanderthal Theory proposes that neurodiversity-traits are of neanderthal origin. So how could the current religious behaviors have evolved? Since major components seems to be recent, but of different origin, it is probably necesary to analyze African/Asian modern humans separately from Neanderthals, and try to figure out what was common before the split of humans into Eurasian Neanderthals and African/South Asian Homo, what evolved later in African/South Asian Homo, what was introgressed from Neanderthal, and how this admixture contributed to today’s religious behaviors.
We today know from many finds in Africa that symbolism, ornamentation and similar behaviors evolved there at the time of the emergence of modern humans. These behaviors group with neurotypical compulsion in Aspie-quiz, and also contain status, reputation and gossip. These are clearly the prosocial dimension of religious behavior described in the book. It works just as well to differentiate an ingroup based on cloth or ornamentation as on supernatural beliefs. In fact, cloth and music taste are the behaviors that often define groups in secular societies. So, it is logical to propose that pre-hybrid modern humans evolved the prosocial dimension of religious behaviors, but probably not in the context of supernatural beliefs, but more likely based on possessings and ornamentation.
When it comes to supernatural beliefs and music, the evidence is in favor of a Neanderthal origin. All the questions in Aspie-quiz about supernatural beliefs cluster together, and when the groups in Aspie-quiz were reduced to six neurotypical and six Aspie groups (with the same names), the supernatural group was merged into Aspie perception. These traits have no relation at all to the prosocial behaviors in neurotypical compulsion.
Aspie perception contains a wide range of more sensitive senses and reduced pain sensitivity. This increased sensitivity developed as a natural adaptation to Neanderthal passive hunting (Aspie hunting). Aspie hunting is closely related to Aspie perception, and contains traits like mimicking animal sounds, making traps and alike. Neanderthal hunting, unlike the group hunting of modern humans, would be conductive to developing a very fine-tuned psychology of the prey animals, including mimicking their sounds and understanding their behaviors. This is called animanism in the book, and it is clearly a neurodiversity trait. It is also the case that stims (called self-stimulatory or repetitive behaviors by psychiatry, but related to Aspie communication in Aspie-quiz) are strongly related to Aspie hunting. Mimicking animal sounds fits both as a stim and as an passive hunting trait. Thus, we might presume that the nonverbal communication behaviors of Neanderthals evolved to be useful for passive hunting and to trick prey animals. This has some interesting predictions regarding mirror neurons that are also described in the book. More likely, the relevance of mirror neurons is not for neurotypicals, but for the Aspie variant of mirror neurons, as it was Neanderthals that adapted their mirror neurons to be extra sensitive to their prey animals, and not modern humans.
When it comes to music, the first musical instruments are found in Europe, not in Africa. These are flutes. Flutes and musical instruments fits well with tricking animals. They still functioned in this way in pastoral settings in Sweden only a century ago. They have no obvious function in relation to the prosocial behaviors of modern humans.
So, it makes sense that highly sensitive senses, musical ability and superior understanding of animal behavior and communication were Neanderthal traits that introgressed into modern humans. These abilities proved useful in their new context, and as a consequence some of the bearers were recruited as shamans, witch-doctors and healers. Later, these “mystical” traits were exaptated into the prosocial behaviors as belief in supernatural things, as people could not understand the extra-sensitive abilities of these people.
Adding to the evidence is that fasting and enduring pain are also neurodiversity-traits. These were traits associated with the shamanistic phenotype.