But the crucial insight into why humans sometimes do very un-Bayesian things is the one that comes next. Sometimes, if a new paradigm challenges a tribe’s most sensitive central beliefs, Bayesian calculations about what individuals and their society will do next break down; sometimes tribes continue to adhere to the old beliefs. The larger question here is whether the Bayesian model of human thinking, when it is taken up to the level of human social evolution, can account for these apparently un-Bayesian behaviors.

Our most deeply held beliefs are those that guide our interactions with other humans—family members, friends, neighbors, colleagues, and fellow citizens. These are the parts of our lives that we usually see as being guided not by reason but by deep moral beliefs—beliefs grounded in sources much more profound than our beliefs about the physical world. In anthropological terms, these are the beliefs that enable the members of the tribe to live together, interact, work in teams, and get along.

The continued exploitation of women and execution of murderers mentioned above are consequences of the fact that in spite of our worries about the failures of our moral code in the last hundred years, much of that code lingers on. In many aspects of our lives, we are still drifting with ways that were familiar, even though our confidence in those ways is eroding steadily. We don’t know what else to do. In the meantime, these traditional ways are so deeply ingrained and familiar as to seem “natural”, even automatic, in spite of evidence showing that they don’t work.

When we study the deepest and most profound of these “traditional” beliefs, we are dealing with those beliefs that are most powerfully programmed into every child by all of his tribe’s adult members. These beliefs aren’t subject to the Bayesian models and laws that usually govern the learning processes of the individual human. In fact, they are almost always viewed by the individual as the most important parts of his culture and himself. They are guarded in the psyche by emotions of anger and fear when disturbed. They are the beliefs and morés your parents, teachers, storytellers, and leaders enjoined you to hang on to at all cost. In fact, for most people in most societies, these beliefs and the morés that grow from them are seen as being normal. Varying from them is viewed as abnormal.

For centuries, in the West, our moral meta-belief—that is to say, our belief about our moral beliefs—was that they had been set down by God and, therefore, were universal and eternal. When we took that view, we were in effect placing our moral beliefs in a separate category from the rest, a category meant to guarantee their inviolability. Non-Western societies do the same.

                                    

                                                          John Stuart Mill (credit: Wikimedia Commons) 

But are our moral beliefs really different in some fundamental way from our beliefs in areas like science, athletics, automotive mechanics, farming, or cooking? The answer is “yes and no”. We are eager to learn better farming practices and medical procedures, and who doesn’t want to win at the track meet? However, in their attitudes about the executing of our worst criminals or the exploitation of women, many in our society are more reluctant to change. Historical evidence shows societies can change in these areas, but grudgingly. (John Stuart Mill, nineteenth-century British philosopher and political economist, discusses the obstinacy of old ways of thinking about women, for example, in the introduction to his essay, The Subjection of Women.³)

These moral beliefs that humans hold most deeply only get changed in an entire nation when evidence shows glaringly that they no longer work. They fail to provide effective real-world guidelines by which the humans who hold them can make choices, act, and live their lives effectively. They fail so totally in this role that the people who hold the old values begin to die out. They become ill and die young, or they fail to reproduce, or fail to program their values into their young, or the whole tribe may be overrun. By one of these mechanisms, a tribe’s entire culture and value system can finally die out. The genes of the tribe may go on in children born from the merging of two tribes, the victors and the vanquished, but one tribe’s set of beliefs, values, and morés—its culture—becomes a footnote in History.