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On Science

Why the past isn't really past

Email|Print| Text size + By Anthony Doerr
November 18, 2007

On Deep History and the Brain
By Daniel Lord Smail
University of California, 271 pp., $21.95

The Age of Everything: How Science Explores the Past
By Mathew Hedman
University of Chicago, 249 pp., illustrated, $25

Early humans were slump-shouldered, slope-browed, hairy brutes. They hunkered over campfires and ate scorched meat. Sometimes they carried spears. Once in a while they scratched pictures of antelopes on the walls of their caves.

That's what I learned during elementary school, anyway. History didn't start with the first humans - they were cavemen! The Stone Age wasn't history; the Stone Age was a preamble to history, a dystopian era of stasis before the happy onset of civilization, and the arrival of nifty developments like chariot wheels, gunpowder, and Google. History started with agriculture, nation-states, and written documents. History began in Mesopotamia's fertile crescent, somewhere around 4000 BC. It began when we finally overcame our savage legacy, and culture surpassed biology.

OK, maybe I'm exaggerating. But to what degree? Modern humans have been around for about 140,000 years. And yet high school history texts ignore, or sprint through, the first 135,000 years.

A Harvard historian named Daniel Lord Smail believes we need to change the ways we organize, and teach, human history. In "On Deep History and the Brain," a dazzling and mostly persuasive synthesis of the humanities and natural sciences, Smail argues for the revamping of traditional "cradle of civilization" styles of teaching Western Civ by reorganizing human chronology as seamless and "deep." A deep history, he says, considers all traces that are relevant to understanding our past, not only more obvious evidence such as hieroglyphics, pyramids, and Herodotus, but also DNA, diseases, vegetable remains, neurophysiology, and phonemes.

Rather than imagining history as fundamentally ruptured between the unknowable Paleolithic and the more modern Neolithic, Smail says, "we should imagine a cone of increasing evidence, swollen but not fundamentally transformed in the past five thousand years by the addition of writing."

Perhaps the most obvious way to recast the narrative of history, Smail believes, is to pursue the biological legacy left to us in our brains. Since genes are fundamentally responsible for constructing our nervous systems, it's fair to say that a deep evolutionary history has helped shape human behavior up through the present day. "Civilizations," Smail says, "did not, could not, invent new forms of body chemistry."

So our brains are built in the same way our ancestors' brains were built. Some of us are scared of the dark, for example, because our ancestors needed to be afraid of the dark. But Smail does not argue that the human mind suddenly adapted 140,000 years ago to succeed on the East African savannah and has been static ever since. Our behaviors, he acknowledges, are not solely shaped by biological inheritance.

Indeed, perhaps the most compelling part of Smail's book is the way he presents the evolution of the modern brain against a backdrop of relentlessly changing environmental and cultural pressures. What he urges historians to adopt is a "neurohistorical" perspective, one in which we understand our genetic legacy while we also remember that we are continuously adapting.

"On Deep History and the Brain" isn't an actual deep history, though, something I'd love to read. Smail explains why a deep history needs to be written and suggests some of its methodologies, but ultimately his new book would serve beautifully only as a foreword to that eventual text.

Meanwhile, Matthew Hedman, a physicist who spends his days analyzing data from the Cassini spacecraft, has written "The Age of Everything: How Science Explores the Past," another book about the intersections of history and science.

Ever wonder how we know with any certainty that the first humans arrived in the Americas about 11,000 years ago? Or that dinosaurs died out about 65 million years ago? Or that the solar system is about 4.5 billion years old? In most cases, scientists deduce the age of very old objects from studying the decay of unstable nuclei. Carbon-14 is the most familiar of these isotopes, and although carbon dating has been around since the 1940s, Hedman does a nice job explaining the physics and pitfalls involved.

In the case of astoundingly old rocks such as meteorites, scientists look first at an isotope of an obscure element called rubidium. But figuring out the age of a meteorite is not as simple as measuring the rubidium isotopes inside. Indeed, Hedman reveals how estimating the age of a 10-pound rock is a puzzle of astonishing complexity, involving a welter of scrupulous calculations and hypotheses about how the entire solar system was formed.

In places, "The Age of Everything" is a technical book, but if you're interested in archeology or astronomy, you might find it fascinating. Hedman is worth reading because he is careful to present both the power and peril of trying to extract precise chronological data. These are all very active areas of study, and as you read Hedman you begin to see how researchers have to be both very careful and incredibly audacious, and how much of our understanding of ourselves - through history, through paleontology, through astronomy - depends on determining the age of everything.

Anthony Doerr is the author of "The Shell Collector," "About Grace," and "Four Seasons in Rome."

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