The American blitzkrieg: a mammoth undertaking

THE AMERICAN BLITZKRIEG: A MAMMOTH UNDERTAKING Our hemisphere's first hunters may have wiped out an

When the first Americans arrived, toward the end of the last iceage, they found North America teeming with big mammals that are now extinct: elephant-like mammoths and mastodons, ground sloths weighing as much as three tons, 4,000-pound, armadillo-like glyptodons, bear-sized beavers, and saber-toothed cats, as well as lions, cheetahs, camels, and many other beasts. These immigratng humans apparently waged a war in which these animals were quickly exterminated -- possibly within just ten years at any given site. It would've been the most concentrated extinction of big ani- mals since, as some theorists hold, an asteroid knocked off the dinosaurs 65 million years ago.

This dramatic confrontation, if it occurred, came as part of thefinale to a long epic in which man, spreading out from his African birthplace, occupied all the habitable continents. Our African ancestors expanded to Asia and Europe more than a million years ago, and from Asia to Australia more than 30,000 years ago. That left North and South America as the last hospitable continents without Homo sapiens.

Even before archaeology uncovered evidence that the first Indians had emigrated from Asia, many scientists suspected that that's what had happened, because the Indians of today look so much like contemporary Asians. A glance at a map shows that by far the easiest route from Asia to America is across the Bering Strait separating Siberia from Alaska. During the Pleistocene ice age, when sea levels were low, it was even possible to take this route without using boats, the shallow strait having become a bridge of dry land joining Siberia to Alaska. The last such bridge existed (with a few brief interruptions) from about 25,500 to 14,000 years ago.

However, colonization of the New World required more than a landbridge: there had to be people living in Siberia. Because of its harsh climate, the Siberian Arctic wasn't colonized until late in human prehistory. The colonists probably came from eastern Europe, where Stone Age hunters in what is now the Ukraine built their houses out of neatly stacked bones of mammoths. Fourteen thousand years ago descendants of these hunters were living in the Siberian Arctic as well, and 12,000 years ago stone tools similar to those found in Siberia appear in Alaska's archaeological record.

After crossing the Bering Strait, these hunters were still separated by one more barrier from their future hunting grounds in North America: a broad ice cap, like the one covering Greenland today, that stretched nearly coast to coast across what's now Canada. At intervals during the ice age, a narrow, ice-free, north-south corridor opened through this wall, just east of the Rockies. One such corridor closed about 18,000 years ago, when apparently there were not yet any people in Alaska. However, when the corridor next opened, 12,000 years ago, the hunters must have been ready, for their telltale stone tools appear soon thereafter, not only at the south end of the corridor near what's now Edmonton, Alberta but also elsewhere south of the ice cap. There, hunters met America's giant elephants and other great mammals, and our drama began.

Archaeologists call these pioneering ancestral Indians the Clovis people, since thei stone tools were first recognized at an excavation in 1934 near the town of Clovis, N.M., about ten miles from the Texas border. Clovis tools have since been found in all 48 contiguous states, and from Edmonton southward to central Mexico. Vance Haynes, a University of Arizona geoscientist, has shown that the tools are much like those of earlier eastern European and Siberian hunters, with one conspicuous exception: the flattish, two-faced, stone Clovis spearpoints were fluted on each face -- a longitudinal groove had been chipped out to make it easier to bind the point to a shaft. It isn't clear whether the fluted points were mounted on spears thrown by hand, on darts hurled by a throwing stick, or on lances that were thrust into prey. One thing's sure, though: the points were propelled into big mammals with enough force that the points sometimes snapped in half and in other cases penetrated bone. Archaeologists have dug up skeletons of mammoths and bisons with Clovis points inside the rib cage; a mammoth from southern Arizona had eight. At excavated Clovis sites, mammoths are by far the most common prey (to judge from the number of their bones), but the bones found at these places indicate the presence of bisons, mastodons, tapirs, camels, horses, and bears, as well.

Among the startling things about Clovis people is how fast they must have spread. Radiocarbon dating shows that virtually all Clovis sites in the western U.S., from Montana to the Mexican border, were occupied within a five-century span beginning about 11,500 years ago. Sites in the eastern U.S. are only a few centuries more recent, and one at the southern tip of Patagonia dates back 10,500 years. Thus, within a millennium of emerging from the ice-free corridor, these people had spread from coast to coast in North America and over the entire length of the New World.