In the 1890s Paul Emil Flechsig, a German brain researcher, published a map showing which parts of the brain developed early in the course of hominin evolution and which parts developed more recently. The motor cortex, for example, evolved very early so that a newborn baby is able to hold onto its mother’s breast and feed. Flechsig divided the brain into 45 areas based on the degree of myelination present at birth. The 9 areas with the least myelination, and which thus evolved most recently, were referred to by Flechsing as “terminal zones”. They include virtually all of the brain areas which make us uniquely human, including the brain areas associated with executive functions and long-term planning.

At the time Flechsig published his findings, relatively little was known about the functions of specific brain areas. With the availability of functional neuroimaging, that has changed dramatically and we now have a reasonably good understanding of the function of many, but not all, brain areas. Also of great importance has been the development of diffusion tensor imaging (DTI) that has allowed us to visualize the major white matter connecting tracts and also assess which tracts developed earlier in human evolution and which ones more recently. Thus, what we now have is a map of the brain with timelines; this can be used to ascertain which areas with what specific function, and connected by which connecting tract, evolved early and which evolved more recently.

As a young man, Charles Darwin was deeply religious and even considered entering the ministry.  During his five-year voyage on the Beagle, during which time he formulated his theory of human evolution, he also “thought much about religion” as he recorded in his personal notebook. In his typical telegraphic writing style, Darwin wrote:

It is difficult to imagine it [belief in God] anything but structure of brain heredity…love of deity effect of [brain] organization.

Thus, many years before Darwin would publish his theory of evolution, he had already suggested that religious belief also had an evolutionary origin.

In Evolving Brains, Emerging Gods: Early Humans and the Origins of Religion I attempted to merge Darwin’s theory with the contemporary neuroscientific evidence concerning the evolution of the human brain. There are relatively well-established theories regarding brain evolution; the uniqueness of the book is the way in which the facts are put together. The gradual development of specific cortical areas and white matter tracts made hominins progressively smarter. We then acquired self-awareness; an awareness of what others were thinking (theory of mind); introspection; and finally an autobiographical memory that allows us to project ourselves backward and forward in time. This afforded us an enormous cognitive advantage over the Neanderthals and all other hominins. However, it also enabled us, for the first time, to fully understand that we would die. Our dreams confirmed that life after death exists and that the afterworld was peopled with our ancestors. Since the ancestors could help us they had to be honored and eventually, the most important ancestors became worshipped. Then, during the agricultural revolution, large numbers of people came together to form towns and then cities. The most important ancestors were arranged in a hierarchy. The greatest of them eventually rose above an invisible celestial line and were regarded as gods, probably between 7,000 and 8,000 years ago. The organization of the major religions followed.

Fuller Torrey, MD is the author of 20 books, including Evolving Brains, Emerging Gods: Early Humans and the Origins of Religion from which this article was adapted. He is the Associate Director for Research at the Stanley Medical Research Institute and the founder of the Treatment Advocacy Center.

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