I am a psychiatrist and researcher on schizophrenia and bipolar disorder. A century ago, a German researcher published data showing which parts of the brain developed early in human evolution and which parts developed more recently. At that time, relatively little was known about how specific brain areas functioned, so it was not possible to interpret the evolution of the brain’s inner workings.
But over the past two decades, brain-imaging techniques — including MRI’s and diffusion tensor imaging — have allowed us to say with relative certainty which brain areas are responsible for specific cognitive abilities — and thus the order in which we acquired them.
Take for example the fact, demonstrated by archaeological evidence from caves in South Africa, that 100,000 years ago early humans began to adorn themselves with necklaces and wear more tailored clothing. Early humans had become aware, for the first time, of what other people were thinking about them. And since we now know the specific brain areas that are involved in thinking about ourselves, we also know when those brain areas developed in the course of human evolution.
As a result, we now have an evolutionary timeline for the development of specific human cognitive traits.
I found this intriguing, particularly because I majored in religion at university. Over the years, I visited many religious shrines, including Europe’s gothic cathedrals, Peru’s platform mounds, and Turkey’s Gobekli Tepe, discovered in 1995 and built about 11,500 years ago as the world’s first known holy place. Now, with a timeline of human cognitive traits, another thought occurred: We might be able to track the development of human religious thought and our beliefs about gods.
So I began to merge the new neuroscience of brain evolution with what is known archeologically regarding hominin behavior. Ultimately I concluded that human thinking about gods probably had its origin in brain developments that occurred about 35,000 years ago.
This period also saw the first unequivocal examples of human burials with valuable grave gods, indicating a belief in an afterlife. At that time humans acquired the ability to project themselves backward and forward in time in a way not previously possible. Psychologists refer to it as having acquired an autobiographical memory.
The acquisition of an autobiographical memory enabled modern humans to understand fully and for the first time that they were ultimately destined to die. Faced with such knowledge, we created an afterlife for ourselves so that death would not be our final end. The afterlife was peopled by those who had died in the past — our ancestors. Proof of their existence in an afterlife came from dreams in which our ancestors sometimes visited us.
Thus began the practice of ancestor worship, which posited that your deceased ancestors could help you. This was probably the main form of religion from about 35,000 years ago until the beginning of the agricultural revolution 10,000 years ago.
When people began to plant crops, domesticate animals and settle on the land, relatives no longer had to be buried wherever they had died, as demanded by a migratory lifestyle. Instead, relatives were buried beneath the family’s house. In some cases the skulls of deceased relatives were displayed in the house.
By 8,000 years ago some skulls were being painted and modeled with plaster so as to resemble a human face, suggesting that ancestor worship was becoming more elaborate and important.
Soon people began living together in villages, then towns and finally cities. Each hunter gatherer group had brought its ancestors to be worshipped, and as the towns increased in size a hierarchy developed among the ancestors, with some considered to be more important than others.
Ultimately a few very important ancestors broke through the celestial barrier and came to be regarded as gods. This probably happened between 7,000 and 8,000 years ago; by 6,500 years ago, when the Mesopotamians were using a written language for the first time, they recorded the existence of several gods.
This was the origin of modern gods and religions.
Just as our genome includes DNA inserted thousands and millions of years ago, so too our brains include ancient functions. By better understanding the evolutionary origins of such functions perhaps we can improve our species.
Dr. E. Fuller Torrey is the author of 20 books, including “Evolving Brains, Emerging Gods: Early Humans and the Origins of Religion” from which this essay, originally published on Zocalo, was adapted. He is the associate director for research at the Stanley Medical Research Institute and the founder of the Treatment Advocacy Center.