Barbara J. King is emerita professor of anthropology at the College of William & Mary. She is the author of six books including “How Animals Grieve.”


Climbers Kevin Jorgeson, in green, and Tommy Caldwell ascend the granite face of El Capitan in Yosemite National Park in 2015. The California peak is part of an ancient mountain range. (AP Photo/Ben Margot)

The continents of our planet glide ever so slowly across the Earth’s mantle, as they have for millions of years. Mountain ranges from the Himalayas to the Appalachians formed when tectonic plates crashed together, causing in turn new weather patterns to sweep across vast regions. But continental drift accounts for much more than this. Together with other geological processes, it powerfully influences how we eat and work today, even how we vote. This theme enlivens the narrative British astrobiologist Lewis Dartnell tells in his new book, “Origins: How Earth’s History Shaped Human History.” Dartnell makes the case that a profound factor in the rise of humanity and civilization has been the dynamic Earth itself.


(Basic)

We owe our very evolution to the Earth. Eons ago, a powerful ripping of the planet’s crust formed the East African Rift Valley, that famous 3,700-mile-long scar in the Earth. As a result, the climate shifted. After about 4 million years ago, grasslands began to replace thick forests, and a dramatic pattern emerged in which “the climate swung rapidly back and forth between being much wetter and then very arid again.” The course of human evolution was forever altered: Our ancestors adapted to the unstable environment by increasingly inventive use of technology and enhanced social cooperation. The periods of most extreme variability, Dartnell notes, are each correlated with the appearance of new species of human ancestors — including the well-known Homo erectus.

Periods of climate stasis make their mark, too. When the vast frozen sheets of the last Ice Age retreated, the Holocene interglacial period brought about warm and wet conditions. The long era of humans’ total reliance on hunting, gathering and fishing came to an end, as the first plants were domesticated. Among them were wheat and barley in Turkey and Mesopotamia; millet, soy and rice in China; squash in Mesoamerica; and maize in Mexico. Wheat, rice and maize still provide about half of the human energy intake today.

As Dartnell moves the narrative along from prehistory to history, he explains the ways in which, at every stage, Earth played its role. During the Iron Age, society was transformed as people discovered how to mold earthbound iron into armor and weapons, and how to clear land using iron axes and plows. Later, in the 15th century, ship voyages from Europe led by men such as Christopher Columbus and Vasco da Gama, and the trade routes established in their wake, were “strongly dictated by the direction of the prevailing winds, and this had profound implications for patterns of colonization and the subsequent history of our world.”

Dartnell’s approach is encyclopedic, marked by both a broad sweep and a passion for details. In the section on wind and ocean currents, this style backfires because the pages become clogged with highly technical terms more suited to textbooks. At other times, though, the facts Dartnell loves to embed are pure fun and may lead a reader to rush up to the nearest person and ask: Did you realize that cinnamon comes from tree bark? Or did you know that when climbers reach the top of El Capitan in Yosemite National Park, they stand on granite that once formed the core of an ancient mountain range? Another wonder: Manhattan’s tallest skyscrapers are clustered in the Financial District, at the island’s southern tip, and in Midtown, in the area of the Empire State Building. Subterranean geology explains why. Schist, a hard metamorphic rock, lies closer to the Earth’s surface in those two places and supports the skyscrapers’ great tonnage.

A problem with “Origins” is Dartnell’s tendency to make exaggerated claims for the power of geological forces over human lives. In the 2016 presidential election, as in numerous previous elections, voters in a “very distinct blue line of counties” in the Carolinas, Georgia, Alabama and “down the banks of the Mississippi” went for Democrats. This pattern is surprising, Dartnell notes, because it deviates from “the wide expanse of red” — heavily Republican voting — found generally in the Southeast. What could account for it? Dartnell takes up environmental determinism in his answer: “The astonishing fact is that this clearly defined band of Democratic-voting areas is the result of an ancient ocean, tens of millions of years old.” This blue-voting area is part of a band of rocks laid down between 86 million and 66 million years ago, shale bedrock from ancient seabeds that allowed for agriculturally fertile soil. Cotton grew abundantly in this “Black Belt” region, originally named for its dark, rich soils. Cotton plantations thrived, in large part because of forced labor by enslaved people. After slavery was abolished, the region remained heavily African American. Rosa Parks, Dartnell says, refused to give up her bus seat to a white person “smack in the middle of this curving strip of 75-million-year-old” rocks.

Despite this nod to Parks, human agency isn’t much present in Dartnell’s account. While he mentions poverty and diminished educational opportunities endured by people of color in the region, he sticks with geology over socioeconomics as the primary explanation for the blue voting pattern.

There’s a certain insensitivity to Dartnell’s language when he alludes to painful parts of the American past. He notes the suffering of enslaved people sent under “abysmal” conditions to the United States during the Atlantic slave trade, then suggests that factors such as “the taste of sweetened tea or a slug of rum” caused Europeans to “close their minds to the human suffering that was ultimately providing for their lifestyle.” Systemic patterns of racist oppression are absent from this account.

No doubt the drift of the continents and the dramatic ripping and tearing of the Earth have influenced our lives. Dartnell is to be credited with demonstrating just how much. But when he elevates geological forces to the near-exclusion of social and political ones, he diminishes the credibility of his argument.

Origins
How Earth's History Shaped Human History

By Lewis Dartnell

Basic.
346 pp. $30