and elsewhere; it appeared to precipitate the disappearance of the Clovis culture and their exquisite elephant-hunting spear points, along with the final extinction of the megafauna. The role of climate and human hunting on this great extinction is discussed in Chapter 9.
Worldwide, very close on the heels of the Younger Dryas, the first efforts at agriculture were germinating on an east-west axis emanating from the Fertile Crescent. Somewhere among a dozen or so places in the Middle East or Asia, someone noticed a plant she wanted to eat growing from a place where she had previously spilled wild seeds.
Another revolution was on its way, probably our biggest—the transition from hunting and foraging to farming—one in which we are still floundering, that was born of that last great blast of climate change, its progress unchecked until the burning heat of present day global warming threatens to bake agriculture out of Africa, out of Asia and banish those crops to the gulags of industrial farming in Siberia.
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A ubiquitous stumbling block in telling the story of the Great Adventure is speculating how and if humans could have lived in North America during periods from which there is no archaeological record. Eastern and western Beringia (Alaska and Siberia) before the last glacial maximum (LGM), about 20,000 years ago, is such a place and time. Ecologists attempt to reconstruct Pleistocene environments by analyzing ancient pollen. Beringia about 30,000 years ago was relatively mild, as indicated from lake sediment samples from Siberia, consisting of bogs and larch-birch forests amid a mosaic of tundra. About 3,000 years later, it apparently turned cold and dry.
Some caution is advised here. Scientists sampling selected lakes for spores and pollen amid a mosaic of varied landscapes don’t always get the big picture right. The plant people may conclude the Late Pleistocene habitat was incapable of supporting people or animals, while at the same time paleontologists are finding fossils of big animals all over the place—suggesting the unproductive tundra looked much like an American Serengeti with its vast herds of hoofed critters. Professionals call the contradiction a paradox. The same kind of critical eye should also focus on the interpretation of the Ice Free Corridor as barren and uninhabitable (Chapter 8) or the use of fungal spores to explain Pleistocene extinction (Chapter 9). Some of the claims are specious.
Thus, scientists debate whether the tundra-steppe of eastern Beringia was too cold and dry for people or animals to survive. Palynologists studying ancient pollen cores concluded the Beringian steppe was sparse, tundra-like vegetation, more polar desert than rich grassland. But fossils dredged up by Alaskans sluicing for gold indicate an abundant animal community and contradict this notion: Bison, antelope, musk ox, mammoth, horses, bears and huge cats thrived in this landscape. Finally, botanists suggested, it might have been cold dry tundra but, unlike the mossy tundra of today, rich in grasses, sedges and forbs.
Topographically, if you subtract the glaciers, the Late Pleistocene landforms looked much like they do today. The ice sculpts the mountains into great cirques and knife-edge arêtes and, as it retreats, deposits terminal and lateral moraine that rivers outwash as broad alluvial fans. The rivers melting out of the glaciers were bigger, wider and more braided than today.
Along the southern limits of the ice sheets you might expect to find a thin ribbon of tundra next to the glaciers and along the tops of mountain ranges. Next to the tundra would be a belt of trees—spruce, fir and pine—and then temperate forests of oak, beech and hickory. Up north, the open tundra and steppes would yield to boreal forests or maybe birch and Populus species.
But this is only a most generalized view; in some places oak forests grew almost at the foot of the ice. Winds blew off the glaciers, picking up sand and silt from the outwash, depositing loess throughout the Midwest U.S. and elsewhere. At the edge of the big glaciers, it was windy and cold but no more inhospitable than today’s Arctic.
Like our present day, species of plants and animals tend to migrate up higher on the mountain and northward as the climate warms. That is, if they can: Five-needle stone pines (like whitebark) clinging to the very tops of mountain ranges today have no place higher to go. Neither does the grizzly bear when the corridor to the next productive habitat is a valley blocked by human development and intolerance.
Maintaining corridors, wild areas and wildlife linkages is absolutely critical if we wish to save species of large animals and mitigate a few of the disastrous effects of the Sixth Great Extinction event—the one we are experiencing today.
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The paleozoologist Valerius Geist called our home: “The predator hellhole which was Pleistocene North America.” He doubted people could have survived (they would have been eaten) in North America until about 13,000 to 15,000 years ago—or whenever the man-eaters went extinct.
Furthermore, Geist notes that not only were those predators huge, but the fossil record reveals many more specimens with significantly healed broken bones and damaged teeth than seen in modern carnivores or African species. He believes this means that the predators really had to fight hard to bring down their huge and formidable prey, that the cats and bears were perpetually hungry and desperate enough to take chances. Also, Geist argues, that the North American prey animals’ “organs of food acquisition and processing remained exceedingly primitive,” so that they remained in low densities and fed on only the best grass. All of which, he believes, indicates the predators were very aggressive.
One might take exception to a generalization or two, but the unmistakable point is that some experts think that Pleistocene predators precluded human colonization of the Americas until just about Clovis times. Geist thinks that the North American mega-fauna, both carnivores and herbivores, impeded human movements in two ways. The grazers created fire-resistant plant mosaics, reducing fuel buildup so that lightning produced only small fires. Humans couldn’t just torch the landscape, like they probably did in Australia, and the great carnivores, the argument goes, used the pilgrims as food. Much blame is heaped at the huge paws of Arctodus simus, the short-faced bear.
Early Americans would have had to live with several gigantic predators, among them sabertooth cats, lions, wolves, huge cheetahs—no doubt the fastest predator on earth—and the short-faced bear. Could people have survived at all and, if they did, would those pockets of early humans have been hunted into extinction by predators, leaving little or no material record of their passing? Or of their genes?
How was it possible to live in the same valleys with this American megafauna? In addition to the short-faced bear, a number of other Pleistocene predators could have been a daily menace to these ice-age hunters. Anyone living in Beringia would have run into lions of the Panthera genus (the African variety but twice as big) who probably hunted in social groups. Wolves, bears and wolverines looking for an easy meal would closely follow the feline hunters.
The abundance of gigantic Pleistocene predators means a lot of killing was going on. There must have been intense competition and interaction around the carcasses of big herbivores. Short-faced bears would have challenged lions and sabertooth cats, with dire and Beringian wolves close behind, shadowed by flocks of ravens, magpies, mobs of buzzards and condors. Grizzlies were around too; probably the entire time humans may have lived in Beringia despite a gap in their fossil record from about 35,000 to 21,000 years ago, which could be attributed to a sampling bias (see Chapter 5).
With humans in Pleistocene America, what was the pecking order? Even if people managed to kill a mammoth or sloth, those other scavenging animals would be close on the scene, especially short-faced bears. And other bears might be in the chase, though not as aggressively as the short-faced variety. Brown bears, over millennia, had learned to defer to humans, even before European firearms arrived, as told in the ethnologies of Western tribes. Early people hunted in groups, growling or roaring when advantageous; grizzlies have never been known to attack a group of four or more people (a technical exception was recorded in July 2011; seven students walking along an Alaskan river trail panicked and ran when they saw a grizzly).
Archaeologists seldom speculate about how people might have fared in such toothy neighborhoods; reasons include not only a general lack of direct evidence but also a pervasive modern ignorance about living with wild animals. North America was not like Africa where early humans and big cats evolved together—no surprises—over a