Who knew of such a thing as a calendar specific to the French Revolution? I obviously missed that session in my history education, or have forgotten it; but it is good to be reminded. And the way it is invoked is an almost-missable detail but essential to thinking about how we, in all our wisdom as evolving cultures, rewrite rules in ways that sometimes moves us two steps backward for every step we had already taken forward. From the New Yorker‘s environment-focused writer, a superb new look at the earth’s history from the unexpected perspective of teeth:

ANNALS OF EXTINCTION PART ONE

THE LOST WORLD

The mastodon’s molars.

BY ELIZABETH KOLBERT

DECEMBER 16, 2013

On April 4, 1796—or, according to the French Revolutionary calendar in use at the time, 15 Germinal, Year IV—Jean-Léopold-Nicholas-Frédéric Cuvier, known, after a brother who had died, simply as Georges, delivered his first public lecture at the National Institute of Science and Arts, in Paris. Cuvier, who was twenty-six, had arrived in the city a year earlier, shortly after the end of the Reign of Terror. He had wide-set gray eyes, a prominent nose, and a temperament that a friend compared to the exterior of the earth—generally cool, but capable of violent tremors and eruptions. Cuvier had grown up in a small town on the Swiss border and had almost no connections in the capital. Nevertheless, he had managed to secure a prestigious research position there, thanks to the passing of the ancien régime, on the one hand, and his own sublime self-regard, on the other. An older colleague later described him as popping up in the city “like a mushroom.”

For his inaugural lecture, Cuvier decided to speak about elephants. Although he left behind no record to explain his choice, it’s likely that it had to do with loot. France was in the midst of the military campaigns that would lead to the Napoleonic Wars, and had recently occupied Belgium and the Netherlands. Booty, in the form of art, jewels, seeds, machinery, and minerals, was streaming into Paris. As the historian of science Martin J. S. Rudwick relates, in “Bursting the Limits of Time” (2005), a hundred and fifty crates’ worth was delivered to the city’s National Museum of Natural History. Included among the rocks and dried plants were two elephant skulls, one from Ceylon—now Sri Lanka—and the other from the Cape of Good Hope, in present-day South Africa.

By this point, Europe was well acquainted with elephants; occasionally one of the animals had been brought to the Continent as a royal gift, or to travel with a fair. (One touring elephant, known as Hansken, was immortalized by Rembrandt.) Europeans knew that there were elephants in Africa, which were considered to be dangerous, and elephants in Asia, which were said to be more docile. Still, elephants were regarded as elephants, much as dogs were dogs, some gentle and others ferocious. Cuvier, in his first few months in Paris, had examined with care the plundered skulls and had reached his own conclusion. Asian and African elephants, he told his audience, represented two distinct species. . .