Daniel Quinn described indigenous people as “living as harmlessly as sharks and tarantulas and rattlesnakes.” (1995) We don’t normally think of predators like sharks, tarantulas, and rattlesnakes as particularly “harmless,” but the harm that they do has a place in a healthy ecology. This seems to stand in stark contrast to the sort of harm done by WEIRD (Western, Educated, Industrialized, Rich, and Democratic) societies, like causing a new mass extinction, (Barnosky, et al, 2011) the sort of blow to the very survival of life on earth previously dealt only by geological processes and massive meteor impacts.

Nonetheless, many scholars ask: does the relative harmlessness of indigenous societies not come from smaller numbers and less effective technology? If they possessed the population or industrial infrastructure of a WEIRD society, would they not do much the same? As Smith and Wishnie put it, “to qualify as conservation, any action or practice must not only prevent or mitigate resource overharvesting or environmental damage, it must also be designed to do so.” (1999) For this reason, they say, indigenous societies do not deserve consideration as conservationists and certainly have nothing to teach us. Our problems require active conservation and industrial-scale solutions to industrial-scale problems. Indigenous societies may have caused less harm to their environments, but only by chance as an indirect result of other forces. As evidence, they offer examples of when those forces fell out of alignment and indigenous societies caused ecological damage on a scale normally inflicted only by WEIRD societies.

The best documented such examples come from Oceania, where as many as 2,000 species of birds — 20% of bird species — went extinct soon after the arrival of the first humans. (Steadman, 1995) Hunting played a significant part. These birds had no experience of human hunters, and so were easily hunted to extinction, just as European sailors would hunt the dodo bird to extinction millennia later. Many other effects followed from other human activities, though, like introducing new species of animals and bacteria and using fire to recreate island ecologies on a large scale. The rate of extinction varied greatly from island to island. New Zealand, for example, while providing some of the strongest evidence that human settlement drove extinctions, also saw relatively few extinctions itself, as its large size, rugged geography, and high rainfall allowed many species to survive until Europeans arrived. (Duncan, et al, 2013)

Such extinctions have inspired an explanation for the Quarternary extinction event about 12,000 years ago, which saw the extinction of 33 of 45 genera of megafauna in North America (73%), 46 of 58 in South America (79%), and 15 of 16 in Australia (94%), but only 7 of 23 in Europe (30%) and 2 of 44 in Africa (5%). This led Paul Martin, a geoscientist at the University of Arizona, to forward the hypothesis that just as human overhunting had led to the extinction of many species in the Pacific, so, too, must Pleistocene hunters entering Australia and the Americas have hunted the megafauna on those continents to extinction. Martin pointed out the precise timing, with the appearance of the Clovis culture, with its distinctively fluted projectile points seemingly designed specifically to kill large mammals, coinciding with the extinction of the megafauna in just a few centuries. He noted, too, that in the places where megafauna had the longest experience with human hunters — Africa, and to a lesser extent, Europe — megafauna survived. Only in those places where humans arrived suddenly, as they arrived suddenly on Pacific islands, did the megafauna disappear.

Martin’s “overkill” theory has become the most popular explanation for the extinction of the megafauna in popular culture, though it does not enjoy quite the same popularity in academic circles, where it has always had its detractors. Of the 33 genera of megafauna that went extinct in North America, we only have sites connecting Clovis hunters with mammoths and mastodons, and for them we only have a few examples. In an archaeological context, those examples may have greater statistical significance than we might expect, but even if we accept that Clovis hunters had “the highest frequency of subsistence exploitation of Proboscidea anywhere in the prehistoric world” (Surovell & Waguespack, 2008), we still lack evidence that they hunted any of the other megafauna that went extinct. We have found more remains from horses than mammoths or mastodons, for example, but none of them show any evidence that human hunters killed them. (Grayson & Meltzer, 2003)

Martin suggested that this lack of evidence actually supported his theory, though. He suggested that human hunters formed a front in a “blitzkrieg” that wiped out megafauna species before they could adapt to the new predator. Martin argued that because of this, human hunters would move too quickly to leave much evidence behind, and so the lack of evidence connecting megafauna deaths to human predation in fact proves that human hunters wiped them out.

Martin did not present a completely unfalsifiable theory, though. He admitted that “clear-cut cases of unbalanced Pleistocene extinction before man” would falsify it, and more recent researchers have found precisely that. Looking at northeastern North America regionally, we see mammals becoming smaller and megafauna going extinct before the appearance of human sites, so that “if human hunters had any input into extinction of Pleistocene megafauna in the Northeast, it was only the coup de grace in a process largely driven by nonhuman mechanisms.” (Boulanger & Lyman, 2014) Of course, at the same time that Clovis hunters pursued mammoths in North America, genetic data tells us that cheetahs in Africa underwent a severe population decline, while reindeer and giant deer went extinct in Ireland, where humans had not yet found their way. (Grayson & Meltzer, 2003) The Quarternary extinctions do seem more correlated with human settlement than climate change, but even those studies that generally support the overkill hypothesis must admit that in Eurasia, at least, climate played a greater role, (Sandom, et al, 2014) and if climate played a greater role there, how can we say that extinctions of megafauna in the Americas and Australia happened solely because of human overhunting?

The earlier dates for megafauna decline and extinction may complicate Martin’s hypothesis more than they falsify it, though, because at the same time we have discovered more and more evidence of pre-Clovis human populations in the Americas, a notion that Martin never accepted. This means that even the earlier dates for when megafauna began to decline and go extinct may still have coincided with human settlement. However, it would also mean that humans lived in the Americas with megafauna for thousands of years, not just hundreds. That would at least falsify Martin’s “blitzkrieg” model, and would put us back to expecting evidence of human overhunting, rather than arguing that a lack of evidence constitutes evidence in itself. If humans lived with megafauna in the Americas for thousands of years, why don’t we have any evidence of humans killing any of the megafauna that died out besides mammoths and mastodons?

In Australia, too, we see evidence that humans may have lived with megafauna for thousands of years before they went extinct. (Brook & Bowman, 2002) Martin suggested that humans hunted megafauna to extinction in large part because the animals could not adapt quickly enough to human hunters, just like the birds native to Pacific islands. This explains why so many more genera went extinct in the Americas and Australia than in Africa and Europe, where megafauna had already had long periods of coexistence with human hunters. Some mathematical models have supported Martin’s theory by showing how small populations of hunter-gatherers could kill enough animals to decimate huge, established populations of megafauna. However, these models have a great sensitivity to prey naivety. Many animals seem to learn and adapt very quickly. With a slightly different number to reflect that, the same models can actually argue against the overkill hypothesis, (Brook & Bowman, 2002) and with thousands of years of coexistence rather than hundreds, this becomes a much more demanding question.

The notion of “mythological Pleistocene hitmen,” as Vine Deloria, Jr. described them, seems to pose another problem. How could the small human populations found in the Americas and Australia ever cause the sort of massive destruction attributed to them, even if they dedicated their lives to killing and coordinated one of the biggest campaigns of organized violence in the history of our species, as the term “blitzkrieg” seems to imply? The megafauna in North America may not have lived at very high densities. They may have existed in a predator-limited system, meaning that “herbivore populations are held at low densities, well below carrying capacity, and the ratio of predators to prey is relatively high.” (Ripple & Van Valkenburgh, 2010) Introducing a new predator, like humans, can throw such a system into chaos, especially when several of the predators involved can switch which prey they focus on in response to the behavior of competing predators. The introduction of humans may have tipped such a delicate balance out of equilibrium, and then “[t]he predators, which were much more abundant than the humans, most likely killed the vast majority of the megafauna” (Ripple & Van Valkenburgh, 2010)

The megafauna populations 12,000 years ago may have existed in a rather fragile state for other reasons, as well. Larger animals require more resources and more space, and so often prove the most vulnerable to extinction. (Gibbons, 2004) The ice age created greater environmental homogeneity, which favored the rise of many new species in the early Pleistocene. As the ice age ended, so did the broad environmental homogeneity that supported so many new species. Perhaps the extinctions that followed simply reset the equilibrium of biological diversity to normal. (Gingerich, 1984)

One of the most ardent opponents of the overkill hypothesis may overstate his case when he claims that “the North American version of the overkill hypothesis lives on not because of archaeologists and paleontologists who are expert in the area, but because it keeps getting repeated by those who are not,” (Grayson & Meltzer, 2003) but it certainly seems true that as accepted as the hypothesis seems in popular media, it has much less currency in academic circles. In her examination of the competing theories to explain the Quarternary extinction event, Robin Gibbons neatly sums up the more common academic view: “If Homo sapiens groups were not present, population numbers might have recovered after an unstable period of adjusting to the new climate and habitat. Conversely, if climate had not already reduced the population sizes of large animals, the relatively small number of migrating Homo sapiens arriving in the New World and Australia may not have been sufficient to decimate entire species of megafauna.” (2004)

This view doesn’t exonerate humans of all involvement, but neither does it support the overkill hypothesis, which places the blame entirely on the voracious appetites of prehistoric human hunters. That such a hypothesis radically oversimplifies the matter seems evident even from the example of the Pacific islands that inspired it in the first place. There predation operated alongside the introduction of new species and the alteration of vegetation patterns to cause the extinctions they did, not alone. (Grayson, 2001) As Donald Grayson put it, the overkill hypothesis “is better seen as a statement of faith about the past rather than as an appeal to reason.” (Grayson, 2001)

After the extinction of megafauna in North America, a new fire regime began. Without the megafauna, more forests and more dense undergrowth may have developed, which in turn may have provided greater fuel for fires. (Gill et. al, 2009) In the context of anthropogenic environmental change, though, this may seem curious. We have only recently begun to understand the scale on which Native Americans shaped the Americas, first and foremost with fire. Charles Mann draws a comparison to domestication in Eurasia, describing “bumper crops of elk, deer, and bison.” (2002) Native Americans created the Great Plains and the Amazon rainforest with fire, sculpting enormous, vibrant ecologies that would afford them a prosperous and abundant life. (Mann, 2002) Might this strategy have begun in the wake of the extinction of the megafauna? Like conservation rewilding today, which argues that since humans hunted Pleistocene megafauna to extinction humans today have a responsibility to restore megafauna to places like Europe and North America, might burning have begun as human beings shouldered an ecological responsibility once borne by mammoths and mastodons?<

Robert Johannes argues that the question of whether or not indigenous people have a conservation ethic often follows a ludicrous pattern. Researchers find an example where an ecological crisis followed from indigenous actions, and then conclude that they possess no conservation ethic. Johannes points out that no society can develop a conservation ethic until they encounter such a crisis and learn that their ecology has limits. He points to effective conservation methods employed by indigenous Pacific islanders, which he hypothesizes emerged as a response to the very extinctions usually cited to indict them. (2002)

For a number of reasons, islands usually have more sensitive ecologies. As noted before, larger islands like New Zealand saw fewer extinctions when humans arrived, but other predators besides humans have caused similar problems in such contexts. When the brown tree snake came to Guam, it caused range reductions and extinctions in native bird populations as well. (Savidge, 1987) When arctic foxes came to the Aleutian islands they preyed on seabirds, which revealed how many nutrients those seabirds transported from the sea to the island interior. Without those nutrients improving soil fertility, the island grasslands became shrub-dominated tundra — because of arctic foxes. (Croll, et al, 2005)

The most well-known example of such a trophic cascade, though, comes from Yellowstone, where wolves had gone extinct by 1930. In 1995, the United States reintroduced wolves to the park. The deer changed their movement patterns to avoid places where wolves might ambush them. Trees began to grow in those areas, where previously deer had eaten all of the young shoots. Songbirds returned to the park to nest in the new groves. Those groves also attracted beaver, which began to build dams that began restoring the hydrology of the park. The very geography of Yellowstone, the course and the shape of the rivers, changed because of the work of wolves. (Monbiot, 2013)

Daniel Quinn did not call indigenous people harmless. He described them as “living as harmlessly as sharks and tarantulas and rattlesnakes.” Predators like those have an impact on the world. Sometimes, like the brown tree snake in Guam, that impact does more harm than good. Sometimes it might seem harmful in the beginning, just as the deer must have considered the reintroduction of wolves to Yellowstone harmful, but in the end produces a more vibrant ecology. In the case of the Pleistocene extinction, or even the ecologies of Pacific islands, it seems difficult to judge. The world lost a great deal, but it also gained a great deal, like the Great Plains and the Amazon rainforest. Indigenous people certainly changed the world. If we can argue about whether or not they really made it better, we can at least agree that they did not make it worse. Humans have always had an impact on the world, and always will, but that impact can take other forms than unrelenting destruction. Like other predators, we can also make the world better, even if we can never live altogether harmlessly. WEIRD societies driving a mass extinction undoubtedly have a great deal to learn from such examples.