Pleistocene Overkill!

An examination of the most annoying argument about the (allegedly) inherent destructiveness of our species --- [Estimated reading time: 20 min.]

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People these days sure do like to argue. But one of the most unnecessary things people are currently divided over is whether humans are “inherently destructive” or not. Despite an estimated 80 percent of global terrestrial biodiversity presently residing in indigenous territories, some people still believe that humans will, given enough time, transform every environment into a moonscape, before – presumably – doing the same thing on the next best planet, and then the next. “It’s simply human Nature, and therefore it’s inevitable,” they say.
But is it, though?

A reoccurring (and unabatingly annoying) nuisance for every primitivist engaging in any debates with non-primitivists is certain people frantically screaming “BUT PLEISTOCENE OVERKILL!” if anyone dares to suggest that hunter-gatherers lived sustainably and in harmony with their environment for the entirety of our species’ existence. Apparently – or at least according to those people – humans have always destroyed the ecosystems they inhabited, and the difference to modern society is that people simply got a lot better at it. They allege that the ecocidal tendencies are not, as we primitivists claim, a relatively recent phenomenon (caused and exacerbated by the inherent anthropocentric tendencies and implications of fixed-field monocrop agriculture), but due to some inbuilt defect that make us humans unable to coexist with Nature.

So what are the facts? What we do know beyond any reasonable doubt is that during the final few dozen millennia of the Pleistocene, in a period spanning approximately 40,000 years (from ~50kya to ~10kya), about 178 species (another source says 100 genera) of megafauna went extinct. The term ‘megafauna’ itself is often defined as animals either weighting more than 100 pounds (~46kg), or, alternatively, over one metric ton (1,000kg/2200lb) – this definition matters to the extent that the former definition includes quite a few more species than the latter.¹

But what exactly caused those extinctions? Well, that highly depends on whom you ask. If you consult the website of the Australian Museum, for instance, you will learn that the extinction of megafauna was “probably due to environmental and ecological factors.”
Yet others have a more specific scapegoat in mind: our own early ancestors.

Whereas some articles claim that “Humans did not drive the Australia’s megafauna to extinction,” and that “Climate change, not human population growth, correlates with Late Quaternary megafauna declines in North America,” others reassure us that, yes, “Early Humans also drove Megafauna Extinctions” and “Humans caused Megafauna extinction in Australia.” It surely seems confusing.

The article on the Quaternary Megafauna Extinction on the popular website Our World in Data includes, right in its introduction, the (of course absolutely unbiased) assertion that

“The lives of our ancestors are often romanticized. Many think they lived in balance with nature, unlike modern society where we fight against it. But when we look at the evidence of human impacts over millennia, it’s hard to see how this was true.”

It sure seems like the author of the article wants to make a broader statement about human Nature – but we’ll get to that in a minute.
Despite the utter ignorance of the fact that indigenous people inhabit some of the most biodiverse and abundant ecosystems (whereas “modern society” most certainly does not), usage of the term “romanticize” is a pretty clear indicator of a likely bias in the author’s thinking, as is evidenced by the following (absolutely unbiased) dictionary definition:

But let’s do the math.

If we go with the numbers from the Our World in Data article (which seems reasonably well sourced), and assume 178 species went extinct in 43,000 years, we arrive at an average of one species becoming extinct every 240 years.
That’s roughly four species per millennium. Even the natural background extinction rate is comparably high – as much as one to five species per year – so whatever “great extinctions” this new, bipedal, omnivorous, dexterous and weirdly hairless predator did cause as it expanded its habitat was well within the limits of what would only be expected in such circumstance (i.e., a capable predator expanding its range).

The debate is far from settled. And the evidence, in its totality, pretty obviously points to a combined effect of both humans and the climate (and an unknown number of other minor factors). But even the fate of the mastodon, so often believed to be a victim of the early Native’s hunger for barbecue, is still under debate. Some assert that their extinction predates human presence in North America, whereas others propose (in a more recent study) that humans arrived much earlier than previously assumed on the American continent, making it likely that they did indeed play a role in the mastodon’s extinction.
Cherry-pick whichever you like.

A few weeks ago, we listened to an interview with population ecologist William E. Rees, in which he blamed human Nature and humans alone for the megafauna extinctions. Bill is usually somebody that I agree with on almost everything he says, but here he perpetuated the same misunderstanding that people on the other side of the ideological spectrum, like the so-called “eco-modernists,” usually bring up. Humans, he says, were behind all the extinctions, because this is just what we do – we inevitably diminish non-human species as we move through the world.

“As [the humans migrating out of Africa] moved, almost everywhere on Earth, what we see is the diminishment of non-human Nature. So as, for example, the aborigines settled […] in Australia, they wiped out the megafauna. So, what humans do when they move into a habitat is alter it completely. The low-hanging fruit go first, […] and eventually they are forced, because of their own depredations on the environment, […] to develop a fluctuating equilibrium with the remnants of the ecosystem in which they have asserted themselves. […] Whenever human beings move into a habitat, they completely change the energy and material flows through that habitat, at the expense of non-human species.” [Emphasis mine]

While he definitely raises some important points (and later clarifies that people are, indeed, able to learn from overstepping certain boundaries – an important factor we will explore in a minute), his choice of words seems a bit over-the-top. The “remnants” of the ecosystems inhabited by hunter-gatherers happen to be the most biodiverse places on Earth, and there is no shortage of civilized persons’ accounts of indigenous peoples’ habitats as basically hyperabundant. Did the Penan of Borneo, the Baka of the Congo rainforest, the Mani and the Senoi of the Malay peninsula, the !Kung of the Kalahari, the Jarawa of the Andaman Islands, and the Pirahã of the Amazon really “completely alter” and “diminish” those ecosystems “at the expense of non-human Nature”?
Judging from the comments of civilized folks visiting them, it surely doesn’t seem like it.

Yet John M. Gowdy (another seasoned academic with whom I agree on the vast majority of issues he talks about), in his phenomenal book Ultrasocial: The Evolution of Human Nature and the Quest for a Sustainable Future, asserts the exact opposite is true. His conclusion is:

“The demise of megafauna has yet to be fully explained, but scientific opinion has swung against the overkill hypothesis. Many studies are flawed because of the lack of precise dates about extinctions, human presence, and climate. But the most careful and detailed megafauna extinction studies point to climate change and the resulting ecosystem disruption as the culprit.”

Considering that extinctions pretty much followed our distant ancestors right in their footsteps – at least eventually – in whatever places they migrated to, I find Gowdy’s conclusion biased and intellectually dishonest. Later in the above-quoted chapter, he correctly identifies why people weaponize the Pleistocene Overkill hypothesis for ideological purposes – yet he does exactly the same thing, by shifting most of the blame on the changing climate to show how “good” we humans are in our Nature. Gowdy then continues to discuss different takes on the issue, but concludes that, ultimately, his view is the right one.
These days, everyone can type their opinion, followed by the word ‘study,’ into google and get a relatively recent result from ResearchGate that seems to support whatever view they hold.² I’m therefore not surprised that most online discussions of the issue quickly descend into a game of “paper ping-pong,” in which each side bombards the other with a barrage of scientific papers that they only read half the abstract of.

Now there are, quite obviously, two camps in this debate: one insisting that humans are gentle stewards of all life, and one maintaining that humans are ruthless butchers.

And at times it surely seems that the side blaming human Nature is winning. The Guardian’s (wannabe) environmentalist and nutter-in-chief George Monbiot regularly makes that same argument, such as in a written debate between him and (recovering) environmentalist Paul Kingsnorth:

“Anyone apprised of the Palaeolithic massacre of the African and Eurasian megafauna, or the extermination of the great beasts of the Americas, or the massive carbon pulse produced by deforestation in the Neolithic must be able to see that the weapon of planetary mass destruction is not the current culture, but humankind.”

Other examples of such a rather pessimistic view abound in an influential paper by Paul Martin, the main proponent of the overkill hypothesis, aptly named “40,000 Years of Extinction on the ‘Planet of Doom’” (*lightning strikes*) :

“Evidently under the destabilizing circumstances of colonization, those who discover new lands ignore accompanying extinctions. Damage control, if any, comes later. The first few hundred years of prehistoric colonization on a pristine continent or island may not be unlike the last few hundred years in America in terms of increasingly destructive economic practices, as viewed by a prudent resource manager.” [Emphasis mine]

But where does this leave us concerning our initial question: did hunter-gatherers mercilessly hunted megafauna into extinction in their quest to dominate and subdue the Earth, or was the changing climate the culprit?
How different people choose to answer this question is not so much a result of determined and unbiased research, but due to their own perception of human Nature. Are humans bloodthirsty killers who want to “dominate” their environment and exploit every accessible resource? Or are we gentle, loving cooperators who deeply care about every cherished fellow living being?

When talking about human Nature, it is important to consider that whatever view most people hold of it is very likely faulty, since it’s not the result of a carefully structured and cross-cultural assessment of humanity as a species, but merely the result of intensive, exhaustive – *drumroll* – introspection. Yep, that’s what usually happens, whether we like to admit it or not. We look at how we ourselves function, feel and think, and consequently project that image onto all other people – which is why debates about human Nature tend to be so unfruitful.
Since human Nature can only be – at its very simplest! – distilled into an extremely complex radar chart of different interrelated tendencies, most people miss the bigger picture when assuming that everyone else is pretty much like them. If you think that humans are rugged individualists who just care about themselves, this is most likely true for you as well. But if you believe that humans are empathetic creatures with an inbuilt tendency towards fairness and reciprocity, you’re also right – for yourself, obviously, and other people who fall on the same end of the spectrum that you do. Human Nature, quite obviously, includes both of those tendencies – and a lot in between.³

And this psychological bias is, more often than not, the root cause for the heated debates between the proponents of the Pleistocene Overkill hypothesis and their opponents: a difference in their assessment of human Nature, subconsciously based on their own personality. This opens up quite a few deeply philosophic questions and actually is a rather complex and profound topic (which would merit its own little essay – which I’m currently writing), but suffice it to say that it can’t be settled by looking at how often prehistoric people grilled large animals.

But back to the discussion at hand.

Let’s consider a highly stylized, but nonetheless descriptive example: if a group of prehistoric hunters pursued a herd of mammoths and managed to drive one of them into a swampy area, where it quickly became immobilized due to its sheer weight and size – who is to blame for the kill? The humans or the climate? Sure, without the humans pursuing it, the mammoth might have never been forced to run into the swamp, or perhaps would have been able to cross it slowly but safely – but without a warming climate, the mammoth wouldn’t have gotten bogged down in the first place. Mammoths, for instance, evolved on (mostly) solid ground (permafrost, seasonally frozen steppe and tundra), and were thus especially susceptible to softer, wetter soil that slowed them down and restricted their movement considerably, while not having that effect on human hunters (or at least not to the same extent).

In the psychological environment of the current culture, dominated as it is by the left brain hemisphere’s utter intolerance of ambiguity and its tendency to divide the entire world into binaries, contradictory scientific theories are – most regrettably – often discussed as polar opposites, binaries of which one must be “right” and the other one “wrong.” I am convinced much nuance is lost in those discussions, and more often than not, the truth is to be found somewhere in the middle.⁴

Trying to moderate between the entrenched fronts of riled-up scientists seething with rage (from my utterly insignificant position in my forest refuge), I’d say the following: we definitely caused some extinctions (perhaps knowingly or even willfully), played a pivotal role in others, and sometimes we might even have been almost uninvolved. But that neither means we are bloodthirsty killers burning through herds of animals before moving on to the next locale once everyone is dead, nor hyperempathetic proto-vegans so in love with other animals that they’d never think about doing them any harm.
When a new, relatively capable and highly adaptive predator emerges on the scene, that a) hunts using tools to increase its fitness, and b) hunts in groups to be even more efficient, some species will go extinct eventually. This is as true for humans as it is for any other comparable predator adapting to life in a hitherto “uncolonized” (stupid terminology) ecological niche. There is nothing exceptional or “unnatural” about that. It just shows again that we’re animals, whether we like it or not.

But that doesn’t mean that we willfully exterminated species after species, simply to assert our dominance. “There is,” as Gowdy points out, “no reason to believe there was an absence of rules regulating exploitation of nature in the Pleistocene. Also, with a lack of markets, an abundance of food for the taking, and a stable population, there was simply no reason to overexploit the environment, and lots of incentives not to.”

Many of the extinctions played out over several millennia, spanning hundreds of generations, and were thus almost indiscernible to the people at any given point during the majority of the time they hunted those animals – “shifting baseline syndrome” comes to mind. Our ancestors weren’t willfully exterminating mammoths because they hated large animals so much and only cared about themselves, they were simply hunting. And a few mammoths less each generation might not even have been that apparent – until it was too late.

The megafauna extinctions were highly regrettable, true, but we have to remember that there are new species evolving and old ones dying out pretty much constantly, and the “goal” of evolution is not, like many vegans seem to assume, to have as many individuals of as many species as possible at all times.

Furthermore, the climate did play a role in many cases. In some instances, humans simply delivered the death blow to a species already under severe distress from climatic shifts, and in many cases it was surely true that the “environmental changes associated with [those] rapid climatic shifts were important factors in the extinction of many megafauna lineages.” But simply concluding, as the authors of the previously quoted study did, that “climate killed off the megafauna” seems, again, pretty far-fetched.

We humans, relatively large mammals that we are, do exploit any given resource to the best of our abilities until our immediate or near-term needs are satisfied – but we are usually kept in check by environmental limits and, more importantly, negative feedback, which we are able to learn from. The resulting lessons are being stored and transmitted culturally, so we can avoid making similar mistakes in the future – various indigenous societies have done so for countless millennia. Knowledge is encoded in ritualistic or spiritual knowledge, or as taboos and restrictions that forbid or limit the harvest of certain plants or animals during some periods, often corresponding to mating and childrearing cycles in the animal population or the seed production/dispersal stage in some plants.

Wherever Native populations have encountered scarcity or even extinctions before, they usually have some sort of cautionary tales embedded into their oral culture. Robin Wall Kimmerer, for instance, tells us about the importance of the “Honorable Harvest,” which includes guidelines like “don’t take the first, don’t take the last,” that instructs people to avoid overharvesting of any resource, or else. Where this overexploitation has happened in the (relatively) recent past, such as with many Native American cultures, this is more pronounced than among people who live in (seemingly) infinitely abundant environments, like the Penan of Borneo. Bruno Manser, living with the Penan in the jungle from 1984 until 1990, recounted several instances in which no conservationist behavior whatsoever was apparent, simply because there seemed to be a limitless supply of those resources. One time, a hunter shot a pig with a poisoned dart just for the fun of it (after already having killed a boar that he was carrying back to their camp when he saw the other animal) without any intention of chasing after it to collect it, another time a group of hunters felled a massive tree (which took them several hours) just to get to the hornbill mother and her chick that were nesting in a tree hollow high above the ground, and yet another time a large fruit tree was felled in order to gather the fruits, because nobody felt motivated enough to climb it.
Nowadays, after witnessing the deforestation of virtually all of their ancestral homelands, the remaining Penan think differently.⁵ In time, we can expect them to codify those hard-learned lessons into stories and myths, to prevent their descendants from overharvesting scarce resources and allow the land to recover from the abuses of the Machine Age.

Trying to paint humans as inherently destructive often serves a rather selfish purpose: people who strongly press this line usually use it to justify behaviors and lifestyle choices that relate to egoistic, unrestrained greed and consumption (often basically amounting to gluttony). Civilization not only encourages but rewards this kind of behavior, and as ecosystems collapse around us, people are looking for a justification that proves their innocence in the slaughter. After all, if it’s just human Nature, there’s really very little we can do about it, right? We just follow our natural instincts!

Yes, usually we do – until we don’t.

The limits we’ve been so busily evading and ignoring over the past few millennia have now, quite undeniably, caught up with us. The year 2023 is – so far – our best piece of evidence.

In Daniel Quinn’s example of the “Hapless Airman” (which I recount in greater detail elsewhere) he explains how this civilization (which he likened to an early airplane prototype and lovingly called the “Taker Thunderbolt”) has been under the illusion that it is flying (and thus free from the constraints limiting all other living beings) – when it has actually been in free fall the entire time.

We humans will exploit any resource to the fullest extent of our capabilities, without the slightest concern for long-term consequences, when we think that we will get away with it.

Once we realize that we don’t, that there will be consequences, we usually adjust our behavior – or simply die out. And this seems to be the choice we’re facing right now. More and more people are realizing that there are, in fact, limits and constraints, and that they seem to be catching up, just as fast as the ground is to the Hapless Airman in Quinn’s allegory. Some people understand this already. More people will understand this over the course of the next few years. And some people probably won’t ever understand it, and choose to go down with the ship. Their choice.

As mammoths and mastodons became harder and harder to find, we can imagine that certain hunting taboos were implemented by at least some human groups, but once the population of any animal species falls below a certain threshold, they are very likely doomed anyway. If something as benign as ‘a slowly warming climate’ or ‘slight changes in the rainfall pattern’ comes along, it might be enough to give that species the rest and send it to the proverbial happy hunting grounds (which, now that I think of it, might not be the happiest place for herbivores). It is highly likely that most prehistoric humans ultimately learned their lesson, even though they may have did so a little too late for the species of megafauna in question.
But what is happening around us right now is that anywhere from a few dozen to two hundred species are going extinct every day – a thousand times the natural background extinction rate – directly caused by the dominant culture of global, techno-industrial civilization. This might easily be the most obvious lesson that our environment ever tried to shout into our faces: we have to stop doing what we’re doing right now (and what we’ve done in the recent past), and slow the fuck down! It’s not working!

The takeaway from all this is that whenever we overstep boundaries, we either learn and adapt – or perish. This is the choice that we’re confronted with – as a species – in the present moment, and that discussion should be the center of the conversation about prehistoric foragers hunting megafauna (and how that connects to contemporary hunter-gatherers’ hyperdiverse habitats): the ability to learn from our mistakes, and to build back better.⁶ We’ve lost far too many species already, and we will lose plenty more even if we were to stop further destruction tomorrow. But that doesn’t mean we should just continue with ‘business as usual.’ Stopping next year is a lot better than stopping in five years, or in ten. Hell, reduction is already a lot better than inaction.

Regardless of what we think about human Nature, how about we stop playing the blame game and ask what hard lessons we modern humans can learn from our species’ extensive, dramatic and quintessentially fascinating history, and the mistakes made, willingly or not, by our ancestors?
That’s what we primitivists are often busily discussing among ourselves, and that’s what really matters at the moment. Our survival, and that of millions of other species, depends on it.

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And, as today’s kids⁷ evidently say, for those that think this was “tl;dr” (did I write that right?), here’s a quick summary:

People argue over who killed large animals, climate or humans.
That discussion is stupid, both killed large animals together.
The real question seems to be if humans are good or bad.
Humans can be both, nothing is black or white.
Usually, humans exist “in harmony” with their environment
(which is better described as a dynamic tension)
just as all other animals do naturally.
But sometimes we need to learn this the hard way.
Right now we are learning it the super hard way
- or not.
Good luck.

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1. According to the former definition, I qualify as ‘megafauna,’ but my wife does not.

2. Not that I allege that’s what Gowdy did – I merely point to the possibility to do that in today’s world oversaturated with research papers supporting any ever-so-quaint opinion (including mine).

3. Actually, any healthy human society should include representatives of both ends of this spectrum, and a robust center of relatively undetermined folks, who decide on a case-by-case basis which direction the group should tend.

4. This is probably true for many other famous (often really passionate) “either-or” debates in science: either Darwin or Lamarck (spoiler: Lamarck is making a comeback), either germ or terrain theory of disease, and so forth and so on. Yet every able-brained person should be able to understand that two theories can both be right about some things - and leaving much to be desired in other respects.

5. As is evident by what they say the many documentaries made about them.

6. Thanks to Joe Biden for this catchy turn of phrase!

7. Shout-out to Leon for the inspiration!