Did early humans wipe out most large mammals?

In ‘The Sixth Extinction,’ Elizabeth Kolbert accepts the claim that overkill by early humans led to the extinction of many large mammals. That charge is politically motivated and there is little evidence to support it.

The last wooly mammoths died about 4500 years ago.

The last wooly mammoths died about 4500 years ago.

Introduction. In his review of Elizabeth Kolbert’s book The Sixth Extinction Umair Muhammad discussed Kolbert’s account of “the eradication of megafauna [large mammals] in Oceania and the Americas by prehistoric societies.” Umair challenged Kolbert’s claim that those extinctions demonstrated humanity’s inherent inability to exist in harmony with other living things.

Two days later, I received a brief note from Michael Friedman, saying that the entire account of a megafauna extinction caused by early humans is based on sketchy and controversial evidence, and shouldn’t be accepted at face value. Intrigued, I asked Michael to elaborate, and he submitted the article below.

—Ian Angus

Michael Friedman earned his PhD in biology at the Genomics Laboratory at the American Museum of Natural History and currently works as an adjunct at City University of New York. His article “GMOs: Capitalism’s Distortion of Biological Processes” was published in the March 2015 issue of Monthly Review.

by Michael Friedman

Kolbert’s writing on mass extinction seems to be based on the Paul Martin/Jared Diamond theory that overkill by early Homo sapiens caused the so-called Pleistocene megafaunal extinctions. I have not read Kolbert’s work, so I’ll limit my response to the Martin/Diamond thesis. Their theory remains controversial, and there have been a number of articles that cast doubt on it.

Most recently, Emily Schwing (2015) reported in Scientific American, that “for at the least the story of the mastodon, we now know for what we call Beringia — Alaska, parts of Yukon and over into northeastern Asia — they were wiped out in those areas for things that had nothing to do with humans, because they all died out before there were humans there.” [“Humans off the Hook for Alaskan Mastodon Extinction”]

The Scientific American report was based on research by Grant D. Zazula et al., published in the Proceedings of the National Academy of Sciences: “American mastodon extirpation in the Arctic and Subarctic predates human colonization and terminal Pleistocene climate change

Donald Grayson and David Meltzer reported in the Journal of Archaeological Science in 2002:

“Today, the overkill position is rejected for western Europe but lives on in Australia and North America. The survival of this hypothesis is due almost entirely to Paul Martin, the architect of the first detailed version of it. In North America, archaeologists and paleontologists whose work focuses on the late Pleistocene routinely reject Martin’s position for two prime reasons: there is virtually no evidence that supports it, and there is a remarkably broad set of evidence that strongly suggests that it is wrong. In response, Martin asserts that the overkill model predicts a lack of supporting evidence, thus turning the absence of empirical support into support for his beliefs. We suggest that this feature of the overkill position removes the hypothesis from the realm of science and places it squarely in the realm of faith.” [‘A requiem for North American overkill’]

In 2008, Todd Surovell, who actually tends to support the overkill hypothesis, wrote, in the Encyclopedia of Archaeology

“Although the overkill hypothesis (or variations thereof) applied to oceanic islands extinctions is generally accepted today, whether overkill explains extinctions on continents remains highly controversial. The most serious obstacle to overkill is that in most regions archaeological evidence for human exploitation of extinct taxa is scarce. In North America, for example, although 33 genera of large-bodied mammals suffered extinction during the Late Pleistocene, fewer than five can be shown to have been utilized by humans. If humans caused the extinction of North American species by over-hunting, then they must have killed thousands if not millions of animals, which begs the question, ‘Where is the archaeological evidence?’ Martin has argued that if blitzkrieg-type overkill happened very quickly, little archaeological evidence would be expected. For others, however, this lack of direct evidence has meant that perhaps we should be seeking explanations for extinctions else- where, such as in the dramatic swings in global climate that have occurred during the Quaternary.” [‘Extinctions of Big Game’]

Finally Matthew Boulanger and Lee Lyman, writing in 2014 in Quaternary Science Reviews, note that:

“The overkill hypothesis requires Paleoindians to be contemporaneous with extinct mammalian taxa and this provides a means to evaluate the hypothesis, but contemporaneity does not confirm overkill. Blitzkrieg may produce evidence of contemporaneity but it may not, rendering it difficult to test. Overkill and Blitzkrieg both require large megafaunal populations. Chronological data, Sporormiella abundance, genetics, and paleoclimatic data suggest megafauna populations declined prior to human colonization and people were only briefly contemporaneous with megafauna. Local Paleoindians may have only delivered the coup de grace to small scattered and isolated populations of megafauna.” [‘Northeastern North American Pleistocene megafauna chronologically overlapped minimally with Paleoindians’]

In 2010, Steve Wolverton provided a useful summary of this debate in the journal Diversity and Distributions: “The North American Pleistocene overkill hypothesis and the re-wilding debate.”

I don’t find it implausible that early humans caused the extinction of some populations, and even entire species, particularly island populations or groups that were bottlenecked by environmental change in the late Pleistocene. I do find it implausible and objectionable to attribute to early humans a monocausal role in global mass extinctions, on the basis of sketchy evidence.

Grayson and Meltzer note that “it is easy to show that overkill’s continued popularity is closely related to the political uses to which it can be put.”

“Take, for instance, Peter Ward’s recent discussion of the matter. Ward — a superb paleontologist whose scientific research focuses on fossils that are between about 300 million and 60 million years old — is convinced by Martin’s arguments, concluding that ‘the ravages of hungry people surely were involved in the destruction of many species now extinct.’ In this conclusion, he finds ‘tragic validity for times approaching … the Snake River salmon is virtually extinct … king crab fishing in Alaska has been essentially terminated because the stocks are gone; the great shellfish fisheries of Puget Sound have been halted because the oysters and mussels are too poisoned by industrial wastes to eat.’ For Ward, the overkill position is inextricably linked to modern times and to the homily of ecological ruin.”

They go on: “Our concern here is that both science and environmental concerns are being done a disservice by relying on claims that have virtually no empirical support.”

I would argue that the politics involved are an effort to exculpate capitalist environmental profligacy, either by conscious defenders of the social order or those who do not have a clear understanding of the dynamic of capitalist production and the “metabolic rift” it entails, and thus, the necessary social solutions.

But, beyond this, I believe the deterministic ideologies that have been bandied about since the days of eugenics, most recently in the forms of Sociobiology and Evolutionary Psychology, are present as a subtext to the overkill argument. These affirm that biology is our destiny and therefore any attempts to alleviate environmental issues by changing society are doomed to failure.

Overkill proponents provide the ad hoc explanation that megafauna in Africa (the cradle of humanity) didn’t become extinct because the large mammals were able to “adapt” to human hunters, which leaves of course begs the questions, why didn’t other megafauna adapt and why is it that now the African megafauna is indeed on the verge of extinction?

Most ecologists would probably acknowledge that the past century has seen an uptick in extinctions and overall reduction of biodiversity. Some will suggest that we are at the precipice of a mass extinction the likes of which haven’t been seen since the K-T event that wiped out the dinosaurs. However, most would attribute it to a variety of factors that are symptomatic of capitalist society, or other things like overpopulation, without actually putting their finger on the dynamic of capital accumulation that drives these symptoms.

There has been a qualitative change in human relations with our environment since the advent of capitalist production, and particularly industrial capitalism. The major causes of biodiversity decline are all related to the commodification and capitalization of natural resources: to expanded reproduction, in Marxist terms. These are habitat destruction, deforestation, factory-type monocrop agricultural and livestock production, overhunting and fishing, pollution, invasive species and the pet trade. Climate change threatens to become another major cause of species extinctions.

I argued in a recent Monthly Review article that,

“Biodiversity runs counter to the very nature of homogenized capitalist production. The dynamics of complex ecosystems are anathema for capitalist producers, who seek absolute control over the production process with the aim of eliminating complicating variables that increase costs of production and decrease marketability.”

Those are the bases for the uptick in mass extinctions. Those are the reason why megafauna in Africa didn’t face extinction until our era (and in this case, we can also add imperialist-fomented wars to the litany of causes).

Contrary to those who seek the answers to destruction of biodiversity in “human nature,” my own experience leads me to the hope that our “nature” lies in the social character and behavioral plasticity of our species, as Stephen Jay Gould argued, and that we can live sustainably in a socialist society.

* * * * *

During the 1980s I was employed by the Nicaraguan Fisheries Institute (INPESCA), where colleagues were involved in an exemplary conservation effort undertaken by the Sandinista government and the UN Environmental Program. Nicaragua has nesting grounds for various species of endangered sea turtles on both coasts. Historically, they’ve been subject to conservation laws, as they are in many places. Seasonally, the local populations rely on turtle eggs for food and income. The local, mostly rural, population consists of peasant farmers and farm workers and their families and small villages reliant on (seasonal) agricultural activity.

The Natural Resources and Environmental Institute (IRENA) was charged with enforcing protection of sea turtle populations. Their novel approach was based on some of the best features of the Sandinista Revolution. First, they carried out consultations with the local communities to find out their needs and the details of the turtle harvest, which were used to elaborate a conservation program. They drew a cadre of “promoters” from the local community groups and the two major agricultural unions, who received training and carried out a conservation education campaign. At its heart, the education campaign was based on the concept that natural resources were part of the people’s patrimony (the “commons”). The conservation program allowed for limited harvest of turtle eggs, while the local grass-roots organizations provided personnel who were trained and charged with enforcing controls on harvesting, what one might call “People’s Rangers.” In short, the rural working population became active participants in the conservation program.

However, this effort would have been impossible without revolutionary social change, particularly the agrarian reform, which provided the rural working population with their own land, seed, low-interest loans, etc., and so something of a secure income and livelihood. The literacy campaigns also contributed to empowering the population, and provision of basic food items added to the campesino’s economic security.

It is crucial that environmentalists and conservationists understand the meaning of experiences such as these. Environmental sustainability, in general, is inconceivable without grass-roots movement, social justice and participatory democracy. This is true whether we are talking about confronting climate change, protecting old-growth forests, halting environmental racism or protecting wildlife. Otherwise we are merely “saving the whales” and replicating the division created between environmentalists and working people who bear the brunt of environmental disasters, but also have the power to create an ecologically sustainable society. The latter is ultimately unattainable without control of state power by the plebeian classes.

A state committed to perpetuating capital accumulation is in existential contradiction with priorities like human health or ecological integration. Moreover, it is incapable of achieving the level of planning and coordination necessary for long-term ecological sustainability and conservation. Even laudable measures and policies such as our National Parks and the Endangered Species Act are piecemeal efforts and subject to constant erosion by market-driven forces.

Posted in Biodiversity, Books & Reports, Featured, Science

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1 year 5 months ago

I thank you for expanding on an important point, but actually I made that point quite clearly in the article. Following the quotations challenging overkill, I wrote:

“I don’t find it implausible that early humans caused the extinction of some populations, and even entire species, particularly island populations or groups that were bottlenecked by environmental change in the late Pleistocene. I do find it implausible and objectionable to attribute to early humans a monocausal role in global mass extinctions, on the basis of sketchy evidence.”

And the quote from the Boulanger and Lyman paper on North American megafauna also affirmed, “Local Paleoindians may have only delivered the coup de grace to small scattered and isolated populations of megafauna.”

One reason your point is well-taken is that denial of *any* agency by H. sapiens in fact abstracts our species from existing ecological relationships and from our very biological being (which is *not* the same as arguing that “biology is our destiny”).

1 year 5 months ago

Michael makes a convincing case here. However I wanted to clarify something that I fear is missing from the article and from these discussions in general. The paleontologist Peter Ward who is mentioned in the piece argues in his book, ‘The Call of Distant Mammoths’ that models of extinction of (say) mammoths based on the idea that they were hunted to death by humans are inaccurate. I don’t have his book to hand, but I think he describes this as the “black hole” thesis, the idea that the animals all entered the mouths of humans. Rather he argues, based on some convincing population modelling that small, but systematic and sustained reduction of animals (I think he suggests the figure of 2%) through hunting can reduce population viability enough to drive some animals into extinction, particularly if there are changing environmental circumstances.

I mention this, not to challenge the general thrust of Michael’s piece, but because I think we have to be careful to not throw the baby out with the bathwater. Crude arguments that simply suggest that humans are inherently destructive, or psychologically programmed to systematically murder animals, are unhelpful. But the opposite is also unhelpful. Humans have always had impacts upon the natural world that they are part of, and even in the earliest times, may have helped to drive some species extinct. What is needed is careful scientific examination of each case, to understand what is causing extinction. We should not assume the ONLY reason for extinction is the involvement of humans, but nor should we underestimate the impact that human’s may have had in the past.

What is important though, is that the political and economic systems they create shape how that metabolic relation to the natural world presents itself. Under capitalism we have the potential for human society to utterly destroy the planet’s ecology. Acknowledging the particularly anti-ecological nature of capitalism should not mean completely dismissing the environmental impacts of previous forms of society.

I did a review of Peter Ward’s book on the Mammoths here http://resolutereader.blogspot.co.uk/2010/07/peter-d-ward-call-of-distant-mammoths.html and I think it’s worth reading. It is far more nuanced than a simple “killer ape” hypothesis, understanding that climate change also played its role.

1 year 5 months ago

As an additional note, I subsequently dug up a Proceedings of the National Academy of Sciences article by Wroe, et al. (2013), “Climate change frames debate over the extinction of megafauna in Sahul (Pleistocene Australia-New Guinea).” Jared Diamond specifically attributed those extinctions to humans. The Wroe article strongly favors a climate change explanation for the extinctions:

“Mounting evidence increasingly points to climate change as the primary driver of Pleistocene faunal extinctions. Many species of megafauna did not persist into the late Pleistocene, and other subsequent extinctions postdated the PGM but were completed before humans arrived. Importantly, a role for humans in the disappearance of any surviving taxa, although possible, is yet to be demonstrated. Extinct species that persisted until or beyond ∼50–45 ka finally disappeared within the context of a rapidly deteriorating climate.”

The implications are interesting. By downplaying or ignoring the role of climate change in large mammal extinctions and favoring a “killer ape” scenario, not only are overkill theorists submerging the role of capitalism in MODERN biodiversity decline, but they are offering climate change deniers a straw man, at least insofar as implications for our, and other, species are concerned.