The Pleistocene Massacres

The Pleistocene Massacres

by Ken Fischman, Ph.D.

History and pre-history are often best told in stories or narratives. There  are two alternative stories to explain the extinction of North American megafauna around 10,000 years ago.
In one story, it was the advent of a land bridge from Siberia to North America, created by the waning of the last ice age, that enabled Siberian hunters to enter and people the Americas. These selfsame hunters hunted the megafauna into extinction.(Martin, 1967).
In the other story, climate changes, transitioning from the last Ice Age, set in place complex ecological forces, which were responsible for the disappearance of mammoths, giant sloths, megabison, dire wolves, and other large mammals (Allen, 2010).
I believe that it matters greatly which of these stories you believe because they enter our cultural consciousness and are responsible, at least in part, in how we see the world. Our understanding of how the world has come to be, in turn influences how we react to and treat the Earth.
Therefore, it is my intention to examine each of these narratives, stating the evidence for them as fairly as I can, while recognizing that I, though a scientist, cannot be perfectly objective, and then to come to some conclusions about them.
In the interest of transparency, I want to state from the beginning that I have a bias toward the climate change theory, but I will endeavor to present both arguments as best I can. I cannot promise though, to present them with the same tone.
So, let us begin. In the first story, which I call the “Pleistocene Massacre” theory, there are two kinds of evidence, one chronological and the other material.
The end of the last ice age, the formation of a land bridge, called Beringia, between Siberia and North America, the movement of human beings into this continent, and the disappearance of megafauna all seem to have taken place at around the same time. This evidence forms the chief argument of the proponents of the massacre theory. This is impressive evidence, but is it sufficient to make definitive conclusions about what happened?
Let us examine this evidence, piece by piece. First, there is the statement that the migration of Siberian hunters to North America and the extinction  of large animals occurred simultaneously. When events occur concurrently, there are at least two possible explanations:
In one, there is cause and effect at work. For instance, if a blizzard were to hit your town and a number of automobile accidents ensued, you might fairly assume that the icy conditions made it more difficult to control vehicles, thus causing more accidents.
Sometimes two events occur at the same time and/or change at the same rate, but it is mere coincidence. For example, a recent scientific paper concluded that people who take large doses of vitamins have a greater mortality, thus showing cause and effect. However, another possibility remains. Did the vitamins cause these deaths or is it possible that people in poor health take more vitamins” How we distinguish between the two in our case is the challenge.
In the so-called hard sciences, like physics and chemistry, the way to distinguish between two such possibilities, is to search for a plausible, and hopefully testable, statistically significant mechanism. Alas, in anthropology and paleontology we usually have less evidence to go by and the opportunity to test these theories is much more limited.
My father used to tell me about the routine of a pair of old-time vaudeville comics. The first one would often recite an improbable story, a whopper, and the other would challenge him. The first would reply “Vas you dere Charley”? Well, we were not there 10, 000 years ago and under most circumstances cannot reproduce the conditions to test them.
I actually do know of one case however, in which a long ago occurrence was tested. Coincidently, it involved one of the animals whose disappearance we are examining here, so I may permit myself a slight divergence to tell you about it, both because of its relevance and because it illustrates the astounding potential of molecular biology to uncover long lost information.

The animal in question was the woolly mammoth (Elaphas primigenius) . As most readers know, some of these animals have been recovered intact from Siberian ice, and carefully examined. One of things noted about them was the intense network of capillary beds in their feet. Scientists reasoned that oxygen, carried in blood, was released in their feet to protect the animals from frostbite at temperatures that sometimes dropped as low as – 60 degrees F. However, how could this occur when hemoglobin (Hb), the blood molecule that carries oxygen, releases it only grudgingly at low temperatures?
The scientists speculated that mammoth Hb was different from Hb of contemporary mammals. But, how could they prove this? First they tried the comparison method. They looked at Hb in the Indian elephant (Elaphus maximus indicus), a modern relative of mammoths. No luck. Elephants have the same Hb that we have. Then they had an outlandish idea. Why not attempt to reconstruct mammoth Hb, using DNA, which they obtained from mammoth tissue, samples? The DNA would contain the gene for constructing mammoth Hb.
They grew the Hb gene in bacterial plasmids, gave it the appropriate precursors of Hb and wondrously produced mammoth Hb. They then proceeded to test the oxygen-carrying capacity of mammoth Hb at low temperatures. They discovered that the mammoth version of Hb gave up its oxygen at much lower temperatures than ours does, and thus would have protected mammoths from frostbite. (Yuan et al., 2011). What shall we call this amazing feat? Molecular Paleontology, or the Lazarus method?
In the absence of an analogous method by which to reconstruct the post-Pleistocene environment, and thus prove or disprove the massacre theory, we are left to sift the evidence, little and conflicting as it is, and to speculate, a lot.

More Evidence for the Massacre Theory:

In addition to the chronological situation, the most convincing evidence for the massacre theory seems to be that there have been finds of enormous numbers of mammoth bones along Siberian rivers and on Arctic islands like Kotelnoi and Liakoff, off the north coast of Siberia. However, there are little or no signs of human activity associated with these bones. Nevertheless, these troves of mammoth bones are often cited as evidence of the destructive tendencies of Paleolithic man. It would seem more likely that some cataclysmic natural event, such as a flood or storm can better account for these phenomena (Vereshchagin, 1967).
As stated previously, the main evidence is the assumption that when man first came to North America, the megafauna disappeared. In order to bolster their case, the proponents of this theory also declare that the Aborigines accomplished the same kind of faunal exterminations in Australia shortly after they arrived there, some 30,000 years ago.
In addition, according to Jared Diamond in his book, “Collapse,” the Polynesians wiped out many native animal species when they colonized South Pacific islands between 400 – 1100 A.D. (Diamond, 2005).
One of the consequences of this line of evidence is that ideologically oriented scholars and media have used it to argue that mankind is inherently predisposed to damaging its environment and exterminating many animals.
With regard to the times that various animals went extinct in North America, there is actually a great difference. For example, Martin cites the demise of the giant short-faced bear (Arctodus sp.) in both North and South America at 20,000 BP (Before the Present). However, among several others, he also lists the American mastodon (6-8,00 BP). He also cites the horse (Equus sp.) as the most common bones associated with man, but states that it became extinct at 18,000 BP (Martin ,1967). Therefore, there is a spread of 14,000 years during which these extinctions may have occurred and some of them happened long before the 11,000 BP Clovis Horizon that supposedly marks the entrance of Siberian hunters on the North American continent.
There is yet another line of evidence, derived from eyewitness accounts of native behavior that appears to strengthen this line of reasoning.
There have been historic accounts from European explorers, traders, and travelers, recounting that they saw Indians set fire to prairies and drive bison off cliffs. According to many massacre proponents, these acts establish that Native Americans were bloodthirsty, wasted thousands of animals, were clearly capable of wiping out North America’s megafauna, and are therefore no better people than we are today. As this story goes, the only reason that they did not totally destroy this continent was that they had not perfected the sophisticated technology with which our society has quickly accomplished that sort of destruction, both in North America and elsewhere. This is what I call evidence by analogy.

Evidence Against the Massacre Theory:

Eiseley’s Rebuttal
Loren Eiseley, was a respected anthropologist and author of many popular science books, like “The Immense Journey” and “The Star Thrower.” At the time when he was the Chairman of the University of Pennsylvania Anthropology Department, he issued a rebuttal to the massacre proponents. (Eiseley, 1943). Here are some of his most persuasive points:
(1)  Not only megafauna died in these extinctions. Many smaller fauna, such as birds, mollusks, and frogs also perished. It is hard to conceive that fires, drives, spears, and atlatls could have killed off such animals. Eiseley emphasized, in particular, the 12-13 species of woodland songbirds that perished (cf.). That extinction certainly cannot be accounted for by the work of big-game hunters.

(2)      Eiseley also points out that many grazing animals survived, such as regular bison, antelopes, deer, elk, and moose.

(3)  Most tellingly, Eiseley states that that there is no evidence of any contemporary hunter gatherers, or even tribal people, using traditional means, significantly decreasing or extinguishing any species.

(4)  Predators and their prey almost always adjust to each other’s numbers, with one increasing while the other decreases and vice versa.  [Classic examples of this dynamic equilibrium are that of snowy owls and arctic hares, and also wolves and moose on Ile Royale National Park, isolated on Lake Superior. To this I  would add the population swings of wolves and elk in Yellowstone National Park which have been intensively studied by Mark Hebblewhite and Doug Smith head of the Yellowstone Wolf Project (Hebblewhite & Smith, 2010).] It is hard to understand why the Paleolithic hunters and their megafaunal prey would not also obey the age-old natural law that no predator can manage to kill off its prey because it depends on the prey for its own existence.

(5)  According to the Bering Straits land bridge story, the Siberian hunter gatherers migrated over it to the New World. Yet, there is no evidence that these Siberian hunters eliminated many of these same beasts where they came from, in Siberia. The same is true for the European Stone Age hunters, Why would they have been able to do so in North America, using the same technology as their Old World cousins?

(6)      It is hard to imagine how small bands of hunter gatherers, estimated at the present time to be less than 2,000 individuals at one point, could have accomplished this task. We know that these small groups existed because molecular biologists have detected bottlenecks in our own DNA (Amos & Hoffman, 2009).  It does not seem likely that the migrating hunters, using traditional weapons and methods, could have even made a dent in these extensive animal populations. It is hard to imagine that they would even attempt to tackle them as long as more vulnerable animals also abounded.)

(7)  When European explorers arrived in the North American continent, they described the land as teaming with game, and the rivers literally overflowing with fish. Just to read the Journals of Lewis & Clark is eye-opening and thrilling. [One explorer in the 17th century walked through what was later named Pennsylvania and described trees throughout his journey so huge that they shut out the sunlight and reduced the understory, making it easy to traverse the entire state. What he was describing was basically a temperate rain forest.]

(8)  The Bartram brothers were naturalists who travelled throughout the southeast of what was to become the United States. One particular episode struck Eiseley in such a fashion that he never forgot it. William Bartram in 1774 was crossing the Saint Johns River in Florida and described it as being so filled bank to bank with alligators that he could practically step on them (Van Doran, 1928).

(9)  In the West, explorers and mountain men found the prairies, forests and mountains were in great shape. Were they exaggerating, as they often did in their stories? The amazing amounts of furs, which they often brought back, testifies to the truthfulness of these statements. [How can this abundance of wildlife be accounted for? Did these Indians lose the skill and blood thirstiness of their predecessors?]

(10)     Large predators, such as saber toothed tigers, dire wolves, and spectacled bears (Tremarctos ornatos) also died during these extinctions. It is hard to imagine that the Pleistocene peoples would have hunted them down for sport, as some massacre advocates have speculated. For example, Steadman (PNAS, 2005), cites evidence on Caribbean islands that sloths went extinct at about the same time, around 11,000 years ago, that Pleistocene hunters entered the Americas as indicative that humans killed them off. Once again, was this cause and effect or association?

(11)     He also failed to take into account that animals are more prone to go extinct on islands because there is little chance that their numbers could be reinforced by in-migrations from other areas as would be the case in mainland North America (c f Quammen, 1996).

(12)     Martin, in a fanciful tale, even went so far as to suggest that little Indian boys shot giant ground sloths, 8 -9 feet tall, for fun(Deloria, 1997). [This does not fit with the eyewitness descriptions I have read about contemporary hunter gatherers. For example, the children of South African Bushman were given toy bows and arrows (without arrowheads) and proceeded to use them on rabbits and other small game, with surprising accuracy] (Fischman, 2012). Needless to say, rabbits and squirrels make more likely game than giant ground sloths for eight year olds.

As stated previously, it is not even certain that man’s first appearance in North America and the disappearance of its megafauna were concurrent  events. It is quite possible that these two events occurred as much as several thousand years apart (cf.). Scholars argue over the dates incessantly and it is clear after examining the literature that methods for dating long-ago events are neither standardized nor agreed upon. We shall see however, that some dates can be established with more reliability than others and that the sequences of some occurrences can be accepted as true with some degree of certainty.
For example, the age of the first North American human migrations continues to be pushed further back into the past than the so-called “Clovis Horizon” hunters, indicted by massacre proponents, at 11,000 years ago. Signs of a pre-Clovis culture, at the Aucila River in North Florida at 14,000 years BP showed well-dated animal bones, and butcher marks. At Paisley Five Mile Park Caves in Oregon there are feces and seeds, demonstrating the existence of a foraging economy at 14,400 BP (Jenkins 2012). The Buttermilk Creek Complex in Texas contains pre-Clovis tools dated 15,500 years BP (Waters et al., 2011). The site at Monte Verde in Chile, (8,000 miles south of the Bering Straight), is now authoritatively dated at about 14,400 – 16,000 years BP (Wikipedia, 2012). There may be even older sites at Meadowcroft, PA, Saltville Valley, VA, etc., but their dates are still in dispute.
The significance of these earlier dates of human occupation is that it raises an important question of why these pre-Clovis hunters were unable to eradicate the megafauna, given their at least twenty five hundred year head start. On the other hand, it could be argued that their cruder lithics (blades, scrapers, and choppers) indicated that their culture was not as technologically (and perhaps strategically) as advanced as that of the Clovis people, and that this made them less proficient at hunting.

Hunting Large Animals:

To my knowledge, no one who claims that Siberian migrants killed off North American megafauna has ever attempted to kill a large and powerful animal, in the open, armed with nothing more than a stone-tipped wooden spear, stone clubs and stone knives.
It is important to realize that these Pleistocene hunters did not have bows and arrows or atlatls (spear throwers), and were not mounted on horses. On the contrary, according to the hypothesis, they were supposed to have also killed off these fleet stallions 18,000 years ago (Martin, 1967) while hunting them on foot.
As I previously pointed out, no contemporary observers were there while these events were supposedly taking place, so how do we know if this sort of hunting is possible, and if so, how efficient it is? Here we are on firmer ground because: (1) some hard evidence of ancient hunting methods does exist, and (2) we can also turn to present day surviving hunter gatherer and tribal cultures to see how they go about their hunting tasks.

There are many eyewitness accounts in the one continent where large herds of grazing ungulates still exist and smaller relatives of mastodons, woolly mammoths and rhinoceroses still roam free. I am speaking of the savannas and rain forests of Africa.Famous European explorers of Africa in the eighteenth century, like Burton and Speke, gave many accounts of the hunting of these animals by African natives, armed with much better weapons than Pleistocene man had at his disposal.
Africans used metallurgy as early as 2,000 B.C.E., and produced iron-tipped spears and knives by 500 B.C.E. They had invented bows and arrows long before European observers arrived on the scene. They coordinated their hunts, using hunting techniques, some of which were borrowed from their observations of jackals, hyenas, and other predators.
North American Pleistocene hunters probably borrowed techniques from wolf packs. Later on, Native Americans admired and definitely copied wolf tactics. For instance, the Pawnee Nation’s scouts were called the “wolf scouts” by other admiring tribes, due to their uncanny proficiency.
By all accounts, hunting large animals on the African plains was dangerous, frustrating, time consuming, and energy depleting. The majority of attempts met with failure. By the way, this is true for most predators, no matter who or where they are.
We have accounts of iKung (African Bushmen from  Botswana) hunters tracking prey wounded by their poisoned arrows for over a day until they literally ran them down (Van der Post and Taylor, 1984).
People who observe predators closely, whether wolves in Yellowstone or lions on the Serengeti, have noted that nine out of ten attacks on prey on the average meet with failure. That is an enormous expenditure of energy and time for rather poor results.
Stone age man might have been more successful than animal predators, due to his strategic abilities and weapons, but he too undoubtedly met with more failures than successes in such difficult undertakings.

 

Only a few animals were likely to be killed in such hunts, certainly not enough to even put a dent in large ungulate herds, which sometimes numbered in the tens of thousands. Such animals, in Africa, even when poached with rifles these days, restricted in territory by the fences and other obstructions of agriculture, and challenged by periodic droughts, have obviously managed to survive in large numbers.
This brings us to the subject of buffalo jumps. Some massacre proponents have cited these as examples of “primitive” people’s ability to employ systematic and efficient methods of killing large numbers of prey animals. These jumps were usually cliffs over which American Indians would attempt to stampede bison herds, in order to drive them to their deaths. Apparently, there were a good many such places in the American West, and we know of some of their locations. Using these tactics, hunters were able to kill large numbers of bison with less effort than hunting them from horseback, with bows and arrows, a method, which was at any rate, not available to Paleolithic hunters.
Some scholars also point out the waste of such a method, often leaving many more dead animals than the hunters could butcher and use for food. In this way, these critics get to make two anti-Pleistocene hunter criticisms at once, one, that these hunters were indeed capable of killing large numbers of animals and two, that they wasted resources.
An amusing story, derived from a Blackfoot legend by Joseph Campbell, illustrates both the difficulty of such endeavors and the reverence and respect in which the Native Americans held Bison, who are accused by some of indiscriminately slaughtering them. (J. Campbell, 1988).
The trouble with these accusations is that they do not appear to stand up to scrutiny. The critics state that these methods were widespread. If so, how successful were the Indians in wiping out the bison? By all accounts, enormous herds of bison, from a population which some have estimated at 50 million animals,(Nowak, 1983) still roamed the American West, even in the 1800s. Obviously, the Indians’ methods were insufficient at the least to eliminate the bison.
In addition, why should we assume that the Siberian Neolithic migrants to North America, who were the predecessors of American Indians, and who had a much smaller population than the Indians, perhaps as little as 2,000 at one point (cf.) , had been more successful in exterminating much larger, and presumably more dangerous, bison (Bison antiquus ) when their ancestors had been unable to do so in Siberia?
And, how did these Neolithic hunters accomplish the permanent demise of dozens of other megafauna? There is no evidence that other animals, such as wooly mammoths  and giant sloths, were susceptible to these stampede methods. How did the paleohunters, for instance, wipe out the large ungulates, such as Bison antiquus, when horse-mounted Indians were unable to do so with their smaller descendents, Bison bison ? Were their Pleistocene predecessors cleverer than they? Hardly likely. In fact, some scholars have argued that ancient Hunter Gatherers were intellectually inferior to us and lived in a sort of preconscious state ( James, 1976), although there exists considerable evidence to the contrary (Fischman & Johnson, 2010)
As for the charge of wasting the meat from animals killed at buffalo jumps, none of the critics have explained how the Indians could have limited the numbers of animals killed, using this crude but effective strategy. Needless to say, our European/American ancestors, shooting bison for sport from moving trains, could have easily limited the numbers killed by that method, but they did not. In fact, they left the corpses of thousands of bison to rot on the western plains as their trains moved on.
( Nature, 2011).

In addition to these senseless killings, it is well known that the wanton killing of American bison was a deliberate and overt tactic employed by our government to remove an animal absolutely essential to the lifestyle (and spiritual well being) of Plains Indians (IUCN, 2010). The loss of the bison forced them onto reservations and opened up the plains states to private property, ranching and agriculture. (Gates et al., 2010). No such motivation can be attributed to the paleohunters, who were just looking for meat.
Observations of native African hunters affords us another opportunity to evaluate these methods, this one of comparison: How did these hunters fare?
Prior to the advent of Bantu agriculturalists and white European explorers and colonists in the 19th and 20th centuries, the Bushmen inhabited the entire region of South Africa. There is recent genetic and archaeological evidence that the Bushmen are descended from the oldest line of human evolution (Gibbons, 2009; Henn et al., 2011). Therefore they have hunting experience in this region for tens of thousands of years.
As previously mentioned, Bushmen hunted large ungulates on foot and employed bows with poison-tipped arrows as early as 24,000 years ago (Zorich, 2012). (The poison used then was the deadly ricin, derived from castor beans). That would seem like a neat, efficient way to dispatch large ungulates, but as they say, the devil is in the details.
Bushmen first had to stalk near enough to edgy herds in order to use their weapons with any kind of accuracy. The poison, now usually made from toxic beetle grubs, worked slowly. The hunters, therefore had to follow or track the wounded animal for hours and sometimes even days before the animal died. I have seen a film of bushman actually running after these animals all day until they exhausted and cornered them (Foster. C. & Foster D.,2000) The stamina of Iron Man competitors and ultra marathoners pales in comparison to that of these hunters. They were then faced with the task of killing and butchering the animal on the spot, and thus heavily laden, had to carry the meat back to their extended families at their temporary encampments.
Keep in mind that the Bushmen are little fellows, most of them barely over five feet tall. Any elk hunter, who has ever shot an elk on top of the mountain or far off the road, can testify as to what a challenging task this is.
Congolese forest pygmies still hunt in their own unique traditional style. The Babenzele pygmies (Mbouti) of Zaire’s northeastern rainforests, have perfected a neat way to hunt in heavily forested areas. It is a cooperative hunt, using nets, made from nicusa vine (Manniophyton) cordage.  The entire group, which is actually an extended family, participates (Sarno, 1995). Each nuclear family is responsible for one section of net, about as high as a volleyball net, but much longer, which they must keep in good repair.
     They put the nets together end to end, the entire apparatus in the form of a horseshoe-shaped trap, covering several acres, by tying it to trees and bushes.

Pygmies are genetically related to Bushmen, and like them, are  also descendants of the longest human lineage in the world (Wade, 2012).
It should be mentioned in this regard, that Anthropologists had long suspected pygmy ethnic antiquity from examining their language and culture. In addition, DNA studies have lately confirmed the ancient lineage and racial interrelationships of the various pygmy groups, such as the Baka and Mbouti, even though these aforementioned groups are separated by more than a thousand miles of forest. (Verdu et al., 2009). This is a testimony to the cohesiveness and relative exclusivity of their cultures and lineage.
Pygmies are also reputed to be efficient and courageous hunters of forest elephants (Loxodonta cyclodis ), which they hunt with spears. These animals are a smaller version of those in large herds ( Loxodonta africana ), which roam the African Savannah.
Australia: Massacre proponents recite virtually the same scenario for the continent of Australia as they do for North America. That is, when humans arrived in Australia, they wiped out the widespread and varied marsupial megafauna. They cite the demise of animals such as the giant wombat, Diprotodon, the largest marsupial to ever exist (Martin, 1967).
However, there is a good deal of evidence accumulating that these two events, the marsupial extinctions and the arrival of Australian aborigines, did not even come close to occurring simultaneously. These megafauna became extinct around 46 – 51,000 BP. However, by some accounts, man has inhabited Australia as far back as 61,000 BP (Brook, 2002,). That would make 10-15,000 years of overlap before these animals went extinct.  It is hard to understand why the Aborigines were able to coexist with the megafauna for such a long time and then suddenly developed methods and desire to wipe them out in a relatively short time. There is no evidence of a change in aboriginal technology.
It is important to note, that like the Bushmen and Pygmies, the Australian Aborigines were hunter-gatherers, who wandered on foot, in small groups of related people, over a landscape, which is mostly a desert, with a fragile ecology. Note, for example, how a recent and continuing drought (Chancellor, 2012) has wrecked havoc with the agricultural and herding economies of that land, despite the availability of modern technology. Australia is almost the size of the USA.
No one knows for sure what the Aboriginal population was before the arrival of Europeans on that continent. The best estimate at the time of first contact was 318,000. (Wikipedia, 2012)
The area of Australia is 2,967,892 square miles. This would have averaged out to one Aborigine/9.3 square miles. For comparison purposes, the least populous state in the US is Wyoming, which has 13 persons/square mile. In other words, it would have taken 121 Aboriginal Australias to match Wyoming’s present population density.
Even assuming that Australia’s population near the coast was much greater than in its desert interior, it is hard to believe that such a tiny population, using Middle Paleolithic technology, could have killed off all of these large animals.
Polynesia: Here the massacre proponents, at first glance, appear to be on firmer ground. The accounts of Polynesian islanders wiping out many species on the islands they colonized are probably true. Nevertheless, this situation may not be relevant to the North American and Australian experiences. It is necessary to put these events in context by examining the special circumstances in which they occurred.
Perhaps the difference that most distinguishes the Polynesian experience, is that these people were agriculturalists, not hunter-gatherers. Their ancestors had migrated down into the Pacific islands from mainland South East Asia (Kumar et al., in press, Kayser, 2008).
They produced large amounts of food and stored it, thus enabling their populations to become much more dense than those of hunter-gatherers. They were prone to population explosions, which put a strain on the carrying capacities of the islands they colonized (Diamond, 2005). It was indeed, their propensity to outgrow their islands’ biological carrying capacities that impelled their long voyages of discovery.
The unique circumstance effecting the Polynesians were their finite resources. They lived on islands, many of them quite small, and when they had used up the local resources, they could not just pick up a few belongings and move to a more promising region as do contemporary hunter-gatherers, like the Hadza in Tanzania and the iKung of the Kalahari Desert. In fact, most of Polynesia was probably colonized from other overcrowded, over-taxed islands. Thus, the impressive, long Polynesian voyages of discovery were probably voyages of necessity.
For example, Easter Island is 3,000 miles from most Polynesian-populated archipelagoes, and despite the romantic notion that these were voyages of exploration and adventure, it is not likely that such arduous and potentially dangerous voyages would be undertaken except in a desperate search for new territory to exploit.
In fact, these overcrowded conditions leading to heavy exploitation of their natural resources were among the primary factors in stimulating new voyages of discovery, as groups of marginalized or land-poor islanders searched for new islands to exploit. Islands have finite resources.
One of the main reasons that many extinctions occur on islands is that once a faunal or floral population drops below a certain level, there is not much likelihood that they will be “rescued” by in-migration. In fact, there is a well-known phenomenon of island dwarfism, by which many species, isolated on islands have a tendency to become much smaller than their mainland relatives (Quammen, 1996). This may be due, in part to the evolutionary pressures brought on by limited resources. Obviously, a smaller version of a rhinoceros or deer would have an advantage in needing less energy. This would be especially true of those living on islands in which their natural predators were never present or had been eliminated, so that their need to grow to a size large enough to defend themselves or flee predators was eliminated.
An extreme example of this principle is the development of flightless birds on many islands., like the Dodo (Raphus cuculatus) of Mauritius Island and the Guam rail (Rallus owstoni). Both of these birds are now extinct due to human activities.
On the other hand, the island of Guam is literally crawling with an introduced predator, the brown tree snake. These snakes originated in New Guinea, and probably got to Guam as non-paying passengers in freighters. The lack of natural enemies allowed this snake population to explode, much the same way as did Yellowstone’s elks after the last member of its original wolf population was killed in 1926.
Human population pressures resulted in a kind of hopscotch invasion of more islands as the Polynesians pressed ever onward towards the Eastern Pacific, until they reached  islands like Easter and Mangareva, which were distant from most of the other islands. The Polynesian’s profligate ways led to starvation and sometimes their extinction when they continued them on such isolated, hard-to-get-to islands (Diamond, 2005).
It is important to compare the Polynesian’s ever-increasing populations with those of Hunter Gatherers, Although we cannot be certain about the life styles of North America’s Pleistocene hunters, we know from geographical, archaeological, and DNA studies that their numbers were relatively small and sometimes led to population bottlenecks of only a few thousand souls. (Amos and Hoffman, 2010). For example, the “Out of Africa “ migration of Homo sapiens to the Near East and Eurasia was calculated to contain only about 2,000 persons.
In fact, Hellenthal et al. (2008), found genetic evidence of at least two migrations, both small, from Siberia to America, the earlier one eventually reaching South America and the later, larger one, arriving in the northwest corner of the continent.
We can also examine the populations and reproductive behavior of these North American migrants’ present day equivalents. Although they are scattered all over the world, and usually have been forced into challenging and impoverished environments by tribal and western technological cultures, hunter-gatherer cultures are remarkably similar in many respects. Their populations, in contrast to those of agriculturalists, like the African Bantus, horticulturists, such as the New Guinea highlanders, and migratory herders like Mosaic and Fulani in Africa, are remarkably stable, both between areas and down through the centuries during the time in which they have been studied.
Their groups usually consist of basically extended families of 10 – 30 persons, who move from one area to another and back again, depending on season and availability of resources such as water, edible plants, and game.
Their numbers are self-limiting, due to biological constraints and their use of a variety of birth control techniques. For example, in ways similar to the game they hunt, they reproduce more abundantly under ideal conditions, and much less so under conditions of stress, such as lack of food and water resources. They also practice late marriage. For instance, among the iKung (Namibian Bushmen), girls do not usually reach menarche and marry until their late teens, while those of tribal agriculturists often do so even prior to puberty.
Pygmies and Bushmen also breast feed their children up to the ages of four or even later. Breast-feeding liberates hormones, such as oxytocin, which block ovulation. This is a natural method of birth control, which has the effect of spacing children so widely that few hunter-gatherer mothers have more than three or four offspring. Contrast this with the families of agriculturalists, who often have as many as ten children. The more the merrier. It takes lots of hands to run a farm, or at least it did until the advent of modern technology. This trend toward large families has persisted even in our culture, into the twentieth century. Witness all the older, large Victorian houses you see, with four, five, even six bedrooms, in rural towns as well as farms.
Hunter-gatherers use other techniques to limit families, which are less savory to our western moralities. They use particular plants for their abortifacent qualities, and have been known to leave newborns to die of exposure, when conditions are particularly desperate for them, choosing to try to save their other children and not add to the stress on them.
So many other, non-game animals disappeared at the end of the Pleistocene that it is hard to argue that the Siberian migrants wiped them out. The extinction of many predators, like the dire wolf and the Miracinonyx, a cheetah-like animal, which relied on its speed to run down its prey, is hard to understand, especially with many herds of smaller ungulates still extant at the time.

The Climate Hypothesis:

The alternative explanation for the disappearance of these large and small animals, interestingly enough, is one that many people today still have difficulty in wrapping their minds around – climate change. In the present case, the reasons for denying the realty of these changes are clear enough. They are first, that these have been mostly predictions of things to come and secondly, accounts of some things that are happening now, but to other people.
In an infamous remark, while he was talking to the chief climate scientist in the world, James Hansen, the renowned TV interviewer, Larry King, asked Hansen when some of these changes would occur. When Hansen told him that some would happen as soon as fifty years from then, King snorted “No one gives a damn about what will happen fifty years from now.” Lamentably, he was undoubtedly right. Humans have apparently evolved to react to present dangers, such as an attack from a saber-toothed tiger, or an algebra test tomorrow morning, and not from future dangers that they may not be around to encounter.

In the case of the Pleistocene, at least no one challenges the reality of these past climate changes, but frustratingly enough, the power of their effects are downgraded in the estimation of the massacre proponents.

Are the Beliefs of Earth-Based Peoples a Valid Guide to Their Behavior?

When we study past cultures, we usually take only so-called hard evidence, such as bones, implements, and ruins seriously. We even define whether a people had something called a “civilization” in such a way as to discount any people unless they had monumental ruins, a written (and decipherable) language, hierarchical social orders with separable skills and duties, and whether or not they made war.
Nevertheless there is additional evidence, which indicates that North American hunters did not exterminate the megafauna. This might be considered “soft” evidence, but I am impressed by it. It takes the form of the spiritual beliefs and lifestyles of contemporary hunter gatherers all around the world, about which we have collected considerable knowledge. As previously stated, I do not think that we attach sufficient significance to the beliefs and observed behavior of Earth-based peoples.
Laurens Van Der Post wrote several books, such as “The Lost World of the Kalahari “and “The Heart of the Hunter,” describing his interactions with the San Bushmen in the Kalahari desert in the 1960s. (Van Der Post; 1958, 1961). Anthropologist Elizabeth Marshall Thomas wrote of her early adventures with these people in “The Harmless People,” and her recollections of her life with them in “The Old Way.”(Thomas, 1958, 2006).
David Abram has written “The Spell of the Sensuous” about the traditional Balinese people (Abram. 1997). James Cowen spoke of the lives and beliefs of Australian Aborigines in “Letters From A Wild State” and “Messengers of the Gods” (Cowen, 1991, 1993), as did Bruce Chatwin(1987) in “Songlines.”
Anthropologist Colin Turnbull turned his attention to the Congo Pygmies in “The Forest People,”and Robert Wolff (2001) wrote movingly of his experiences with the Sng’oi of Malaysia and other aboriginal hunter gatherers in that part of the world, in “Original Wisdom.”
This is only a partial list, and I only have space to summarize a few stories and legends to give you an idea about people who found a way to tread softly upon the Earth and  to live in communion with the world.
I will begin with an Australian aboriginal legend called “The Kadimakara,”as retold by Cowen (1991)
“According to the Aborigines, the desert they must cross to reach the oasis at Cullymurra water hole was once a vast region of fertile plains and forests. traversed by rivers flowing into lakes. The bones of ancient animals which we call Diprotodons scattered en route  were the surest proof that conditions had changed since that primordial moment …
The present clear sky above had once been filled with dense clouds of dust, which perpetrated tropical downpours at regular intervals. Great Gum trees reached high into the sky, supporting a complex interlace of green life which shut out all sunlight.  From this arboreal vault a group of monsters known as the Kadimakara descended in order to feed on the fruits below. Once these creatures had tasted the fruits of the Earth their appetites became insatiable.  In time they had eaten all the shrubs, trampled the Earth hard, and finally had resorted to eating the giant trees down which they had come. In an ironic twist of fate they had destroyed their one escape route to the heavens!
As a result, the Kadimakara were forced to remain on Earth.  They wallowed in the lakes, drinking up the water.  They ate everything before them.  Soon the canopy of trees overhead had been destroyed, revealing one continuous hole of blue sky.  The tribesmen named it Pura Walpinina, or the great hole. Meanwhile, the Kadimakara began to die of starvation  now that they had eaten every shrub and bush.  In the heaving marshlands of putrefying earth which had once been rivers and lakes the monsters lay down to die.  One by one they expired, their bodies slowly petrifying in the relentless sun, which their destruction of the natural environment had released upon the Earth.  Their bones, the bones of the Kadimakara, littered the dry earth as somber reminders to the surviving tribesmen of what can happen when the natural environment is treated as an inexhaustible larder The Kadimakaras’ insatiable appetites had been the direct cause of their own extinction.
Perhaps the aborigines were warning themselves that if they exceeded the carrying capacity of this fragile, barely livable area, they would suffer the fate of the Kadimakara.
On the other hand, perhaps this cautionary tale is meant for ears other than those of aborigines who have lived in harmony with the Earth for so long.  Perhaps this myth is of more recent origin, say since the days of first contact with Europeans and observation of their peculiar appetites.”
Here is another story, from a very different place. This legend was told to James Cowen by an islander, living in the Torres Strait, between New Guinea and Australia. His family was reputed by other natives to “own” the Pleiades (Seven Sisters) constellation (Cowen, 1993). How can one own a constellation? Read on and find out.
“Tagai was a man.  He owned a canoe, along with his friend, Kareg.  One day they were out fishing with a crew made up of Usiam and Seg people.  To you these people are the Seven Sisters and the stars in the belt of Orion.  Anyway, while Tagai and Kareg were paddling along, the Usiam and Seg people decided to eat all the food and drink all the water on board.  Kareg saw this happening and called out to Tagai, who was in the bow of the boat.  So Tagai strung the Usiam together and tossed them in the sea.  He did the same to the Seg people.  Only Tareg, his friend, remained with him in the boat,”
“Yeah, the story of the stars belongs to me. I must interpret it for others, to remind them that all of us must take care not to act like the Usiam and Seg people.  By drinking too much, by eating too much, we forget to leave some over for others.  The food and water on Tagai’s boat represents nature. If we use it up without thinking, we run the risk of exhausting our food supplies on the voyage.”
I have trouble with people who tell me that the only reason that Native Americans and other indigenous peoples did not destroy their environments just as thoroughly as we seem on our way to doing, is that they lacked bulldozers and insecticides.
I find it hard to believe that people who regarded the rivers as their sisters, would have raped them by pouring toxic waste into them, or their forests as brothers, would have clear-cut them. Explain to me how people who looked at wolves as older brothers and whose scouts emulated them, like the Pawnee and Cheyenne did, would have turned around and shot them from helicopters if only they had they possessed such equipment
Every one of these sources, without exception, tell the same story. These hunter gatherers are remarkably like ourselves. In fact, they are us. Biologically, we are still living in the Pleistocene. They are not Rousseau’s “noble savages”. They were capable of anger, envy, voraciousness, and all the other dark emotions  that people of our society exhibit. However, by both happenstance and planning, they created a lifestyle that discouraged those darker behaviors and valued the best human qualities, like cooperation, egalitarianism, and community.  These qualities enabled them to tread lightly upon the Earth and to live lives of integrety. We have much to learn from them.

The Tale of The Blind Men and the Mammoth:

Some respected researchers, like William Ripple of Oregon State University, who first opened our eyes to the dynamics of wolf/elk interaction in Yellowstone, believe that human predators may have been involved in the extinction of the wooly mammoth. Ripple and Van Valkenburgh (2010), presented evidence that mammoths may have fallen victim to trophic cascades some 10,000 years ago.

Trophic cascades are ever-widening, usually top-down effects brought about by interactions between living organisms in ecosystems, particularly originating with predator/prey relationships. Interestingly, we are at present witnessing damaging cascades which are caused by a world-wide loss of predators. This, in turn, is mostly due to human disruption of ecosystems, such as the effects of shark slaughter on fisheries.
Ripple and his co-workers examined wear and fracture rates of fossil carnivore teeth and from growth rates of their prey, Heavily worn and fractured teeth are an indication of bone consumption, which predators avoid except when there is prey scarcity. There was little indication of such wear. Their evidence suggests that there were no serious food shortages in northern America 10-15,000 years ago.
They believe that a range of predators, such as the dire wolf, lions, and saber toothed cats (Smilodon sp.) reduced the number of fauna. This system was balanced but dominated by the predators. When humans arrived however, they provided increased competition for these predators.         Giving an example of a modern equivalent of this situation, these authors state that in contemporary Alaska, human hunting of moose caused wolves to switch to sheep, which in turn, resulted in a precipitous decline, not only of sheep, but eventually of wolves and moose. [Ripple et al. make it clear that this trophic cascade started with that apex predator, man].
The Pleistocene predators, now desperate for food, may have finally driven their prey to extinction. This conclusion, however, goes against one of the primary dicta of wildlife biologists, which is that predators never cause extinction of their prey.  Before that could happen, the predators themselves would decrease in number from lack of sufficient prey to sustain themselves (cf.).
The authors argue by analogy that human whale hunts have resulted in Orcas switching to seals and sea otters. This, in turn has led to an explosion in sea urchin populations and a decline in kelp forest ecosystems, in another contemporary trophic cascade.

Dwindling green Pastures:

Allen and his colleagues, however, recently reported that a massive reduction in grasslands and the spread of northern forests may have been the cause of the Pleistocene decline in mammals. This occurred during  and after the height of the Ice Age, 21,000 years ago, and dramatically reduced available food.
It resulted in the reduction of large mammals across northern Eurasia and North America by 11,400 years ago, although some held on for several thousand years longer in limited localities, termed “refugias,” in which both climate and food supplies were more amenable to their survival. Migratory hunters were also restricted to these areas by availability of these mammals for their own food supply. Several refugias have been identified, strung along the coast of what is now called Alaska and British Columbia.
These researchers have reconstructed the environment from ancient pollen records and noted which major megafauna became extinct and which survived. The wooly mammoth, cave lion, giant deer, wooly rhino and cave bear went extinct. The brown bear, elk, moose, reindeer, saiga antelope, and musk ox survived (Allen et al., 2010).

We are all connected:

Another group of scientists, (Nogues-Bravo et al.,2008) have accomplished what amounts to a synthesis of the last two views. They used climate models and examined fossil distribution, concluding that change in global climate was exacerbated by human pressures to drive the mammoths and other megafauna to extinction.
These researchers used a number of climate models, ranging from 6,000 to 126,000 years ago. Clearly, the environment was much worse for mammoths 126,000 years ago, yet the animals survived. They showed though that there was a catastrophic loss of habitat 6,000 years ago so that only 10% of the former habitat remained.
They also considered the effects of temperature changes and rainfall. They then compared these parameters with age and distribution of fossils.
Nogues-Bravo and his colleagues say that mammoths faced rising temperatures and increased hunting pressure at the same time. They argue that that these animals had faced previous temperature increases without going extinct and that the only difference was that this time there was human influence.
They came to the conclusion that  it was a combination of climate change and human hunting that was responsible for these megafaunal extinctions.

Conclusions:

Well, I have come to the place where I need to sum up the evidence and tell you of my conclusions. However, it is not as easy to do as I first thought. I started out on this journey pretty sure of myself. I was on the side of the angels – at least they were my angels. I was pretty sure that the massacre proponents had at best exaggerated their case and at worst had become prisoners of their ideological propensities. .
The last few papers I have cited impressed me, both with their approach and their reasoned arguments. I was most impressed with the work of with Ripple and his co-workers because they had a novel approach to this difficult subject, and due to my respect for Ripple’s past work.
Perhaps you will be surprised that when I evaluated  the worth of these publications, I took into account who wrote it. At first sight that does not seem to be objective, so I will let you into a little secret of science. It matters who did the investigation. In over 30 years of scientific research I found out that not all the facts are published and that the devil is often in the details. I that learned that I could trust the intelligence, thoroughness, and integrety of some researchers more than others.
Ripple is one of these. As I mentioned previously, his salient work was accomplished by tracing trophic cascades in Yellowstone National Park from wolves to elk and to their widespread and important effects on the rest of the ecosystem. Ripple showed that the elk population explosion, that occurred after the last wolves were exterminated in 1927, had deleterious effects that ranged from the disappearance of riparian flora to decreases in bird, fish, and scavenger populations, and that the wolves, reintroduced in 1996, have been an important factor in restoring balance to the entire system.
Nogues-Bravo and his colleagues seem to have nicely combined the ideas of Ripple with those of Allen et al., who emphasized the important role of climate change.
Nevertheless, despite Ripple’s analysis, I think that the preponderant evidence supports the idea that humans were not responsible, or played only a small roll in the demise of these animals.

The following points sum up the basis for my conclusion:

• Human signs were usually not associated with the massive troves of mammoth bones found on Siberian islands.
• The extinctions took place over a very long period, some of that including times when man was apparently not present on the continents of North and South America.
• It was not only the charismatic megafauna that became extinct during this period, but so were other animals, that were unlikely to have been eliminated by hunters. One example of this is the dozen or so species of woodland song birds that went extinct.
• The direct ancestors of these hunters did not eliminate many of the same animals in Siberia.
• It is hard to believe that such a small number of people, around 2,000 at one point caused by genetic bottlenecks, could have killed off so many animals.
• Later on, Native Americans, with much more advanced technology available to them, put hardly a dent in the populations of megafauna, especially the immense herds of bison, whose numbers may have reached as high as fifty million animals.
• North America was occupied by these Siberian migrants over a much longer time than previously thought, at least 14,000 years, and so the question arises over why it took them such a long time to eliminate the megafauna.
• African megafauna have survived native hunters, who had much more advanced technologies than the North American migrants did.
• Australian aborigines were also few in numbers. They entered that continent much earlier than massacre proponents thought, and coexisted with the marsupial megafauna there for 15 – 20,000 years.
• The Polynesians, who exterminated many native fauna, were islanders and agriculturalists, two factors that make extinctions much more possible.
• Hunter gatherer beliefs and spirituality make it improbable that they would treat their environment in as ruthless a fashion as our culture does.

In conclusion, I do not think that that the last word has been said in this controversy by any means, but the idea that the demise of the megafauna was due, not to one, but to a combination of factors, including climate change and perhaps anthropogenic action, seems like a more likely answer to this vexing question.