As mentioned previously in my review of Barbara King’s Evolving God, religion is a pervasive phenomenon, and many scholars have put forward explanations of how, when, and why it arose. The arguments King put forth did not convince me that religion is anything more than a by-product of our evolution. Apparently, so did Darwin. Though believers often like to point out Darwin was a Christian too, he struggled to reconcile the two and ultimately lost his faith. American psychiatrist E. Fuller Torrey gracefully acknowledges this intellectual heritage and here updates this idea, putting forth the convincing argument that religion arose as a by-product of brain evolution.

In Torrey’s view, religion arose after the brain had undergone five specific cognitive developments. The first half of the book walks the reader through the archaeological, anthropological and neurobiological evidence for each of these. Without wanting to go into too much detail, these steps and their most important supporting evidence were:

– increased brain size and intelligence around 2 million years ago (complex tool production)

– development of self-awareness about 1.8 million years ago (cooperative behaviours such as hunting and living together, requiring an awareness of self and other)

– development of theory of mind (i.e. the ability to imagine what it’s like being someone else) about 200,000 years ago (caring behaviour by Neandertals and presence of the brain regions required for theory of mind tasks, judged from skull shape)

– development of introspection (i.e. the ability to think what others might be thinking about you) about 100,000 years ago (archaeological evidence for self-adornment such as jewellery).

– development of autobiographical memory (i.e. the ability to project yourself forward or backwards in time) about 40,000 years ago (rapid improvement in tools and weapons, cave art, and intentional burial including valuable grave goods).

In each chapter detailing these steps, Torrey adds a wealth of supporting neurobiological evidence in the form of data on skulls, postmortem and imaging studies comparing primate and human brains, and cognitive development of children. It turns out that each of the above cognitive developments requires evolutionarily younger areas of the brain. But wait, doesn’t that smack of Haeckel’s discredited idea of ontogeny recapitulating phylogeny? At the beginning of the book, Torrey points out that, yes, the strict interpretation of this idea has been discredited (see amongst others Gould’s Ontogeny and Phylogeny), but Haeckel wasn’t completely off the mark either (see my review of Haeckel’s Embryos: Images, Evolution, and Fraud). There are broad parallels, especially in human cognitive development.

I imagine the development of autobiographical memory scaring the living daylight out of our ancestors, as we could now conceive of our own mortality. It would be a cheap shot to say “no wonder they invented gods”. Instead, Torrey spends quite some time describing the rise of agriculture and domestication, echoing some of the sentiments that Scott raised in Against the Grain about it not being a neat and linear process. The reason agriculture and the ensuing sedentism matter is that the dead were buried close to the living. And indeed, deceased ancestors became very important to the living, with rich evidence of mortuary rituals and ancestor worship. It’s a small step from there to viewing powerful ancestors as god-like beings. As with agriculture and state development, Mesopotamia is where it all started for religion too, and Torrey documents how they became entwined. He also shortly reviews the rise of gods in other early civilizations.

“I imagine the development of autobiographical memory scaring the living daylight out of our ancestors, as we could now conceive of our own mortality”

Evolving Brains, Emerging Gods has many strengths. The book is very well structured, both as a whole – showing a logical organisation in discussing the various stages of brain evolution – but also at the lower levels. Chapters come with short summarising paragraphs and make good use of headings and ornamental breaks to separate sections within chapters. Torrey uses the introduction to explain brain morphology and its terminology, and includes boxes and appendices to explain other things that are important. And there is a good use of illustrations of brain regions throughout the book. His writing also exemplifies the humbleness one would expect from a conscientious scientist. He immediately acknowledges the main idea did not originate with him, but with Darwin, and the last chapter of the book briefly summarises various other theories for the origins of gods and religions, how they relate to each other, where they overlap, and where he thinks their explanatory power falls short. This section, and the accompanying references, are incredibly useful to explore this topic further (I marked various books for future reading).

But the biggest strength of this book, in my opinion, is that Torrey doesn’t bring an ideological agenda to the table. For many people this will obviously be a controversial topic, and the religion-as-by-product-of-evolution explanation is also espoused by Dawkins in e.g. The God Delusion. But there is no vitriol in this book. And, as he mentions in his preface, Torrey is no stranger to the feelings evoked by religious experiences. He has no need to rant, a calm and reasoned exposition of his arguments will suffice. I admit that as a (reasonably militant) atheist myself, and as an evolutionary biologist who thinks that people sometimes give adaptationist explanations undue weight, the by-product explanation is one that resonates strongly with me. But even with that bias in mind, I don’t think it’s an overstatement to say that Evolving Brains, Emerging Gods makes a very convincing argument. And the fact that the book avoids polarising the topic with unnecessary anti-religious sentiment will hopefully see many more people read it.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

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