Chapter 8

, we can never hope to date early man at all exactly by means of elephants or bison or any other extinct mammal. Even if science were able to settle the time of the great extinction, we should be only a little better off. We could say that man was in the New World at that time; but this would give us only an upper date, not a lower one. Man may have been here for tens of thousands of years before those mammals died off. A few scientists think he was.

The great glaciations presented early man with an opportunity and a difficulty; they threw a land-bridge across Bering Strait, but, for long periods of time, they also laid a barrier of ice and snow across his path to the south. Look at the map at the top of page 26 and you will see that about 65,000 years ago the barrier covered the whole depth of Canada. This would have meant a trip of some 2,000 miles across ice. For a time, as we have explained earlier, a corridor opened up for his passage. By 18,000 years ago, however, it had closed again. To be sure, there was a tongue of ice-free land that ran southward across part of Canada and shortened the journey over snow and ice to a thousand miles; but the invader would have had to be extremely lucky to hit the upper end of the open country. Far more important, none of the animals that he hunted, and that therefore led him on his southward journey, would have taken that thousand-mile trek across a frozen, foodless waste. If early man came in the time of the corridor, his trip would not have been too difficult and he would have found game along the way. At any period he could have come by boat or possibly afoot along the Pacific coast. But, no matter how he came, he would have faced almost insuperable difficulties during the first quarter and the third quarter of the last glaciation.

This fact affects different students differently. Antevs, feeling that man must have come after the ice began to melt, gives our migrant not much over 15,000 years in the New World. If man arrived earlier, he feels, it must have been when the corridor opened through the ice some 40,000 years ago, and he sees no evidence for so early a migration.[21] Kirk Bryan disagrees. Accepting the theory that the last glaciation waxed and waned three times, he places the first invasion by man in the second of these wanings, or inter-stadials, just before the final burgeoning of the ice 12,000 years ago.[22] Sauer goes further. He suggests that the shores of western Siberia may have been inhabited during the second interglacial, and that during the third glaciation, preceding the Wisconsin, “a first colonization of the New World is not improbable.”[23] Erwin H. Barbour and C. Bertrand Schultz say that “evidence is constantly accumulating to show that man actually had reached North America before the last glacial advance.”[24] George F. Carter believes that artifacts in the glacial gravels of Trenton and Lake Lahontan, spear points with musk oxen in New Mexico, the Vero skull partnered in Florida with flora and fauna more appropriate to Pennsylvania, stone implements deeply buried under aged soil profiles, all argue that man was in North America during the last glaciation. He does not believe that primitive hunters—let alone the Cochise food gatherers—would have survived Arctic travel at the height of the glaciations. He thinks that Folsom man came through the ice-free corridor of 40,000 years ago, and that another body of immigrants came during the last of the three great interglacials, which means about 100,000 years ago.[25]

Interglacial migration finds support from Albrecht Penck, the German glacialist who with Eduard Brückner established the four great glaciations of central Europe. Penck gives two reasons for believing that man came to the Americas in the last interglacial. Both theories lie outside his field of special knowledge.

First, Penck doubts that man had time enough after the glaciers melted to adapt himself to the seven or eight climates in which he lived and labored in 1492. In the 10,000 years since the Wisconsin glaciation, people of an arctic habitat could not possibly have adjusted their physical nature so perfectly “first to forests, then to steppes and deserts in temperate zones, then to steaming tropical forests and to the plateaus of the tropics, the steppes and deserts of the southern hemisphere, and finally to the damp, cool south.”

Penck’s second reason for supporting interglacial migration has to do with the marked changes of climate that took pace during the Great Ice Age. As the glaciers grew and moved farther and farther south, the temperature belts of Canada and the United States moved south with them. As these belts moved, vegetation altered. Tundra crept to the south, pursuing grasslands and forest. Deserts and jungle moved before them. When the glaciers began to melt, this movement went into reverse. Penck feels that primitive man migrates easily only within a single climatic zone. Tundra folk avoid forests; forest folk avoid tundra. Man moves with the climate, not against it; a New Yorker goes to Florida in the winter, not the summer. Early man would not have traveled southward through Canada and the United States while the climate was moving northward with the melting of the ice. On the contrary, man would have moved southward only as the glaciers grew and the temperature belts moved southward. When the glaciers melted he would have tended to move northward again. Thus man must have entered the New World toward the end of an interglacial, and gone southward with the weather. After that, shifts in the climate would have distributed man all over the Americas. “Under the influence of a number of alternating glacial and interglacial periods, we can understand the gradual settlement, but not solely on the assumption of one glacial migration.” With the end of the last glaciers men spread north and south once more, and even drifted back to Asia.[26] Penck’s argument becomes all the stronger if we grant that early man followed the animals he killed for food and animals followed the movements of the vegetation on which they fed.

Further, the presence of early man close to the time and even the edge of the retreating glaciers—if the evidence is read aright—argues that he must have arrived in North America during one of those retreats of the Wisconsin glaciation which preceded its final growth and decline.

Geological Evidence and the Pluvials

All this is speculation, of course—reasoned speculation, but no more than that. Are we on firmer ground when we deal with geological evidence? Perhaps, yet there is plenty of room for controversy.

The New World has very few sites in which artifacts or human bones have been found in glacial gravels. A noted one, near Trenton, New Jersey, has been under dispute for eighty years. The Lake Lahontan site and its blade have been too much neglected. There are, however, a number of places where skulls or artifacts have been found linked to other strata than gravels that suggest a relationship with glacial activity.

In these sites we find human skulls or artifacts together with signs of much rainfall or of large lakes and rivers which now have no more existence than the mammoth. The evidence of man lay undisturbed beneath sterile layers of material deposited by water. A typical case is Sandia Cave. Here Folsom points were found beneath a floor of a stalagmitic limestone created by so heavy a seepage of calcium-charged water that the stratum holding the Folsom material had been partially consolidated. Below lies another sterile layer—of yellow ocher earth, indicating a very moist period and the presence of trees which would provide certain chemical agents and which are no more common now in this arid area than are heavy, continuous rains. Another example of mans association with a much moister time than the present comes from the cave in Brazil where the Confins skull was found. The skull lay under six feet of alluvial soil carried in by water. Later a layer of stalagmitic limestone sealed the sepulcher. It may be presumed that artifacts found on the shore or in the clay of Lake Cochise, Lake Mohave, and Pinto Basin—now dry and gone—must have been made during a time of great waters.

What do such evidences of unusual moisture mean? They mean that the men of these sites lived before or during a period of heavy rainfall not known there for at least the last 9000 years. Beyond that bare fact, debate begins. Walter, Cathoud, and Mattos, who described the Brazilian find, took a most conservative attitude and wrote that Confins man lived “a few thousands of years ago.”[27] Bryan, who studied Sandia Cave, placed the later wet period after the end of Pleistocene, or Great Ice Age, and the first wet period—along with the Sandia points—in the Late glacial.[28]

Glacial experts call a period of unusual and widespread rains a pluvial. They believe that the growth of the glaciers was accompanied by pluvials, and some maintain that pluvials also marked the melting of the ice. Antevs lists a great pluvial—the Bonneville—which formed Lake Bonneville and Lake Lahontan during the first maximum of the last, or Wisconsin, glaciation, 65,000 years ago. He places another period of great moisture, the Provo Pluvial, at the last glacial maximum, about 12,000 years ago, and believes it was all but spent 7,000 to 9,000 years ago.[29] Thus he dates Lake Mohave and its early artifacts about 9,000 years ago. His point is that annual precipitation is about the same throughout the globe, but that the pluvials shift at various times. “It is essentially the location of the rainfall that changes.”[30]

All authorities do not agree that annual rainfall is constant, and some deny Antev’s late date for the last pluvial. Sauer writes, “I know of no climatologic basis for postulating a postglacial pluvial period,” either in New Mexico or the Lake Mohave and Pinto Basin area of southern California.[31] Some European authorities believe that pluvials are entirely glacial. M. C. Burkitt, for example, cites the fact that the same type of tools is found in Africa during pluvials as in Europe during glacials.[32] According to Simpson’s theory of the formation of the glaciers, rainfall increased enormously during two periods of the Great Ice Age; the last pluvial was at its height during the building up of the Würm-Wisconsin ice sheets. (See page 58.) The pluvials make a rather good case for early man in the New World during the last glaciation.

In Sum

Ten years ago, we knew that men in America had once killed, skinned, and eaten animals now extinct, for we had found their weapons and a few of their bones mingled with the fossils of mammals long extinct. We could not question the association, because it often involved the remains of campfires; spear points and bones might be moved about in the course of time, but not fragile heaps of charcoal. We knew, too, that the bones and tools of man had been found sealed away by the chemistry of the ages. But when we tried to date man securely by animals that were dead and gone, or by the earths that lay above him, we began to guess. The guesses of conservative glacialists gave him at least 15,000 years in the New World. Other speculations—supported by rather plausible evidence as well as not implausible theory—placed him still earlier. Now, at last, through the miraculous time clock of radiocarbon, we know that man was here before the chill of the last Ice Age settled upon the land.

REFERENCES IN THE TEXT

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