Friday, November 18, 2011

Bottlenecks, migration, and the development of religion

We’ve gone through a watershed change in our views of the origins of humanity in the past 15 years or so. The old opinion of the stereotypical “cave man” was brutish and unintelligent, and was based on the Victorian notions of the Great Chain of Being and the Progress of Cultures that culminated in them. This myth has been difficult to counter, much less dispel, but it’s driven research striving to prove or disprove it.

Evolutionary psychologists attempt to understand our ancestors in terms of the challenges of their environments and their adaptations to them (Wilson, 2000; Sapolsky, 2004). In the case of modern human beings, this can be problematic, as we must base our assumptions on what they left behind that got preserved as archaeological evidence. And there’s not a lot of it.

Essentially modern human beings have existed since around 120,000 – 130,000 years ago (Tattersall & Schwartz, 2001). Decoding of the human genome in the 1990s boosted the exploration of ancient DNA and the development of “molecular clocks” for mutation rates on the mitochondrial (female) and Y-chromosome (male) DNA. Examination of certain mutational markers in the DNA has confirmed humans were around in the time frame referenced (Olson, 2002; Sykes, 2004; Wade, 2006).

We’ve found women’s mitochondrial DNA markers converge on a time around 140,000 years ago in East Africa, to an individual woman or related group of women whose DNA has passed down to us all (Wade, 2006; Sykes, 2004). Men’s Y-chromosome markers converge on 59,000 years ago (Sykes, 2004). This doesn’t mean that both sexes didn’t exist without the other between 140,000 and 59, 000 years ago, but rather that these particular sets of founding genes survived in everyone alive today. It is unfortunate that these people are called “Mitochondrial Eve” and “Y-Chromosome Adam,” because the idea is misleading.

The fossil record is based on random elements that survived down to the present for study. DNA studies use blood or saliva from modern people to address evolutionary history, or in rare cases, they can examine the actual DNA of specimens who’ve been found (Wade, 2006). Tools are one category of things that survive well, especially when made of stone. We can confirm that modern humans lived around 170,000 years ago based on the types of tools found with fossilized individuals (Wade, 2006; Olson, 2002). Interestingly, during this period we shared the earth with a population of Neanderthals living in Europe and Western Asia and a population of Homo Erectus people in the Far East and Indonesia (Tattersall & Schwartz, 2000). There were three kinds of human beings, and they all used an identical set of stone tools essentially unchanged for thousands of years (Wade, 2006).

At this point, a bottleneck occurred. An island volcano in Indonesia blew up in the largest supervolcanic eruption in human history. The supervolcano blew sometime between 73,000 and 73,500 years ago, with a Volcanic Explosivity Index (VEI) of 8. To compare, the Tambora eruption in 1815 that caused the “Year without a summer” of 1816 only had a VEI of 6, where VEIs are scaled as 10 times greater with each increase in VEI level. A six to ten year volcanic winter ensued, causing massive die-offs of populations around the planet (Ambrose, 1998; Tattersall & Schwartz, 2001; Dawkins, 2010). The eastern population of Homo Erectus died out almost entirely, leaving only relic populations such as the “Hobbits” of the Island of Flores (Dawkins, 2010). Similarly, the Neanderthals were greatly pared back, and the remnant populations moved southward into the Levant blocking migration routes out of Africa (Wade, 2006, Finlayson, 2009).

Our species was knocked down to less than 10,000 people, of whom only about 5,000 were fertile, breeding adults. East Africa suddenly seems very big when you’re trying to find food in a ravaged environment, and trying to find a mate to bear your children (Wade, 2006). Human behavior patterns seem to have changed around this time in ways more profound than just new toolkits. Prior to the eruption of Toba, humans appear to have lived in gender-separate groups more than in family units, much like out ancestors, the chimpanzees. There is some evidence that we may have had similar cultural attitudes, as well (Sapolsky, 2004; Wrangham & Peterson, 1997; Smith, 2007).

After Toba, relationships changed to favor extended family groups (Wade, 2006), possibly to counter the difficulty involved in finding partners. Living in extended family groups promoted other changes to the mind of human beings, causing behaviors more like the bonobos (pygmy chimpanzees) of Central Africa, who use social interactions as a means of cementing relationships among group members (Sapolsky, 2004; Smith, 2007).

I suspect that in addition to changes in our tool kits, culture, and patterns of settlement, this may be the point at which Goddess worship, particularly of the Moon, began to be celebrated. This kind of evidence doesn’t fossilize, and it’s hard to infer from the bones and other remains, but we can think about it as consistent with some of the beliefs we share now about the Moon as Mother.

For instance, She regulates women’s menstrual cycles, and when females live together in groups, they tend to synchronize their cycles with each other (Smith, 2007; Diamond, 1992). These people were modern humans, just as intelligent as we are, and I cannot believe they would not have connected the two—especially as fertility was so crucial to the survival of the species.

Most of what little we know about Stone Age religious beliefs comes from the last Ice Age, such as the cave paintings of Europe, some kinds of markings on bone, statuary, and other objects. The cave painting phenomenon seems to have originated in Europe, sometime after 30,000 years ago. Other painted images are associated with the San in South Africa, and with the Aboriginal inhabitants of Australia (Fagan, 1998). DNA studies based on blood samples from around the world indicate that two principal lines of people remained in Africa, while a small group of 150 people (or less) migrated out of East Africa to populate the rest of the world (Wade, 2006).

Those ancestors appear to have crossed the Red Sea at its southern end, crossed southern Arabia into India, and then to Australia by around 50,000 years ago. This migration occurred at a walking pace, generation by generation (Wade, 2006). Only later did people migrate north and to the west into Europe via the steppes of Asia, reaching to the Atlantic by around 30,000 years ago (Finlayson, 2009). There were a couple of reasons for this: first, Europe was populated by Neanderthals who most likely prevented earlier migration, and second because the Ice Age was moving toward another cold peak at around 20,000 – 25,000 years ago (Roberts, 1998).

As humans developed techniques to adapt to cold environments, they eventually migrated into Siberia and the Americas. By 12,000 years ago, the ancestors of today’s native peoples had reached the tip of South America (Mithen, 2003). The final migration involved the peoples of Polynesia from Southeast Asia across the Pacific between 3000 BCE and 1200 CE (Wade, 2006). As our ancestors inhabited new territories and environments, they developed gods, myths, legends, and ritual practices suited to their locales and cultures (Fagan, 1998; Mithen, 1996).

Could the two bottlenecks through which humans passed on the way to inhabiting the Earth have fostered the development of religions? In the case of the Toba eruption, women who could bear children suddenly became rare, precious, and extremely valuable. Associating her with the Moon, and the Moon with the ultimate female, the Goddess, is a natural leap. The second bottleneck involving the small group who migrated out of Africa brought humans into contact with vastly differing environments to which they had to adapt. It becomes natural to try and propitiate and coerce the local spirits of place toward helping people survive there.

While agriculture appears to have arisen in the Levant area of the Mediterranean and spread outward, along with centers in China, South America, and Central America, it appears to have spread as an idea more than as a population shift. For example, in Europe agriculture was adopted by six of seven population groups that can be traced back to a specific clan mother, while the 7th appears to have entered from the Levant (Sykes, 2001). These clan mothers are likely to be the origins of various faces of the Goddess that arose in different places, and the populations comprised the early matriarchal cultures of Europe.

So there appears to be a connection between our changing understanding of how people populated the earth and the places and times that religious beliefs arose. Bottlenecks provide forcing factors that highlight those things most frightening and most precious to be celebrated and propitiated. Different environments drove people to create spirits and deities suited to the landscape, and ultimately to the variety of religious experience we know about today.


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Dawkins, R. (2010). The Greatest Show on Earth: The evidence for evolution. New York, NY: Free Press/Simon & Schuster.

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Wrangham, R., & Peterson, D. (1997). Demonic males: Apes and the origins of human violence. New York, NY: Mariner Books.

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