Origins How The Earth Made Us

Origins asks one question: how did the Earth make us? More accurately, like a six-year-old whose curiosity cannot be sated, there lies a series of recursive “why” questions at the heart of this book. Astrobiologist and science communicator Lewis Dartnell takes a big history look at human evolution and especially civilization, seeing how far down the explanatory rabbit hole he can go. Time and again, he grounds his answers in geology and geography. You would be forgiven for thinking this sounds like what Jared Diamond attempted more than two decades ago, but calling it Diamond-redux would not do it justice.

Dartnell takes as his starting point the evolution of Homo sapiens in East Africa. He subscribes to Maslin’s ideas for where and when we evolved, outlined in The Cradle of Humanity. The gist of his argument was that it was a combination of plate tectonics and climate. The geography of the African rift valley and pulses of climate variability interrupting longer periods of stability led to regional lakes rapidly appearing and disappearing. This unstable environment favoured adaptability and intelligence. Dartnell similarly gives a revealing geological explanation reaching back 55 million years for how the most recent ice age came about and how it has impacted human dispersal around the world.

Now, it is easy to accuse a popular science book like this of glossing over subtleties for the sake of a good story. I therefore appreciated that Dartnell clearly signposts there are frequent disagreements on the details of the story of human evolution, and that not all evidence points in the same direction: his narrative represents the consensus view. He is nuanced enough to point out what that may seem rapid and purposeful – humanity's global migration starting 60,000 years ago – was, in fact, a matter of trial and error. I liked his suggestion that there may have been earlier attempts at migrating out of Africa, or developing agricultural civilizations, that simply fizzled out before taking off. Similarly, when he brings up the effects of the Toba eruption on early humans (see my review of When Humans Nearly Vanished), he immediately flags this up as controversial. All this gave me a good feeling about the balance Dartnell is trying to strike between presenting a captivating narrative while sticking to the facts and how best to interpret them.

From this point forward, the remainder of the book deals with the last 10,000 years of human civilization, making excursions into deep time explanations where needed. For readers of Diamond’s Guns, Germs and Steel this is perhaps more familiar territory as he discusses the rise of agriculture (see also my review of Against the Grain for some nuanced counterpoints to the standard narrative) and livestock husbandry. Here he reaches back into deep time to explain why Eurasia ended up with so many more domesticable species compared to the Americas, and why the orientation of the continents made the spread of agriculture easy in Eurasia (which is oriented East-West), but hard in the Americas (which is oriented North-South).

With agriculture came trade and Dartnell chronicles the establishment of the first maritime and overland trade routes, leaning heavily on overview works such as The Sea and Civilization and The Silk Roads. His interest is in how these were shaped by the geography of the seas (the shape of coastlines, the existence of naval bottlenecks) and the land (the ruggedness of the terrain, microclimates). And he explores how our subsequent maritime Age of Exploration, when Western nations started colonising countries around the globe, depended on, and was shaped by, the planetary patterns of ocean and air currents, in turn shaped by where plate tectonics has parked the continents currently.

In the same vein, he spends two chapters exploring the deep origin of the materials we use to build and construct with (whether architecture or objects and tools), how they are formed, how they have ended up distributed over the world the way they have, and how that has played into the fortunes of civilizations and nations. He talks of rocks and metals and does an excellent job explaining our current dependence on rare earth elements and platinum group metals (see also The Elements of Power), expressing concern about our continued appetite for these resources.

Finally, he gives a quick tour of energy (see also Energy and Civilization) and how we transitioned from muscle power to wind and water power and then fossil fuels, taking the reader through the age of coal, the steam engine and then oil. Here, too, he is specifically interested in how these resources were formed and why they are found where they are found. From reviewing Energy: A Human History and Carboniferous Giants and Mass Extinction I was already familiar with the fact that 90% of the coal we have used since the Industrial Revolution was formed during the Carboniferous, some 360-300 million years ago (leading Dartnell to ask the same question as Rhodes in the former book: what if that had not happened, would the Industrial Revolution still have taken off?) But Dartnell provides a lucid geological explanation to the question why so much coal was formed then. And it turns out there was a similar period in which the vast majority of the world’s oil reserves were formed, again for a good geological reason.

In his book The Equations of Life, Charles Cockell wrote that physics is life’s silent commander, setting hard limits on what evolution can and cannot do. I would argue that Dartnell here similarly convinces that geology is history’s silent commander. Very accessible and full of interesting ideas, Origins is a worthy contender in the saturated market of big history and environmental history books. Depending on how much you have read on this topic, not everything here will be novel, but I do think that with its deep time and geology perspectives, Dartnell goes a few steps beyond most books.