Megafauna: A Tribute to Paul Martin

Paul Schultz Martin never resented his critics. “He spent his professional career,” as Vance Haynes put it a few days after Paul’s death on September 13, 2010,  “inviting criticism,”[1]  I got my first chance to see Paul’s reaction to that “invited” criticism at the American Museum of Natural History’s 1997 Extinction Symposium: it was good-natured, courteous and completely free of condescension.

Paul was, in short, the most collegial of men. When I look back over our 14-year acquaintance, I can think of only one occasion in which he showed anything like professional envy. That human little moment was an appealing one though, and I miss him a great deal, now, as I think back on it: I was on the phone with him from Johannesburg, talking about the work of Wilhelm Schüle of the Freiburger Institut für Paläowissenschaftliche Studien.

Schüle had been the first person to endorse Paul’s theory that a member or members of the human family had exterminated several large-animal species in Africa before Homo sapiens had left Africa and spread into the rest of the world toward the end of the Pleistocene.[2] In doing so, Schüle made some interesting and original suggestions. He reasoned, in particular, that Africa’s giant tortoises must have been even more vulnerable to growing hominin ingenuity than the large mammals that succumbed to that ingenuity midway through the Pleistocene, some 1.4 million years ago. It made sense, therefore, (Schüle’s argument ran) to expect that Africa’s giant tortoises would have disappeared some time before that first wave of mammalian extinctions. And that, he pointed out, is in fact what happened:[3] Africa lost its giant tortoise species in the later Pliocene.

Partly because some of Schüle’s writings are in German, which Paul (his Pennsylvania deutsche antecedents notwithstanding) didn’t read, and partly because illness had diminished the range of Paul’s research by that time, he was hearing about this reasoning for the first time. Before I could get halfway through my account, though, he interrupted with an unexpected “Damn, damn, damn!” Startled, I paused. “Why,” he continued, “didn’t I think of the tortoises!”

* * *

I first contacted Paul in 1995, after I had decided to write a book about the new perspective on our species’ ecological history opened up by his work. In preparation for that writing, I had been researching the late-Pleistocene extinctions in the New World, Eurasia and Australia, together with their Holocene counterparts in Madagascar, New Zealand, and other oceanic islands. Despite the fact that I had no formal scientific training, Paul took my efforts to understand his insights seriously from the start. I was surprised and delighted when he started giving me the same kind of guidance I had received from an inspiring professor ─ H.R. (“Bobby”) Hahlo ─ while doing graduate work in law at McGill University years before. I was a bit disconcerted, however, when Paul suggested, with the gentle kind of firmness that doesn’t yield to misgivings, that my research should include the megafauna which disappeared from Africa in the earlier parts of the Pleistocene.

I had wanted to focus on Paul’s well-known theory that humans had exterminated the biggest animals of North and South America soon after they entered those continents near the end of the Pleistocene. It was a satisfyingly dramatic hypothesis, and also, I felt, a credible one. I was aware that Paul believed that members of the human family had also had a hand in the disappearance of a number of big-animal species from Africa earlier in the Pleistocene, but such an immense period of time had elapsed since those extinctions, that they would have had to have been caused by a predecessor of Homo sapiens ─ H. erectus, perhaps, or maybe even one of the australopithecines. A scenario like that could never, I felt, amount to anything more than an interesting conjecture.

Paul didn’t see it that way. For him, the idea that members of the human family were responsible for the extinctions which diminished Africa’s megafauna long before the Late-Pleistocene megafuanal exterminations on other continents, was nothing less than the keystone of his global overkill theory. If humans and their precursors had, after all, been a benign, non-destructive presence in the earlier Pleistocene, (a universal assumption, as far as I can tell, before Paul turned his attention to this question) then why, he asked, would Homo sapiens suddenly have started causing extinctions when it left the African continent toward the end of that epoch, and entered the previously uninhabited land-masses of Australia, Boreal Eurasia, and the New World?[4]

I had done little more than skim Paul’s Africa and Pleistocene overkill article which had appeared in Nature in 1966.[5] Still in dissertation-supervisor mode, Paul told me to read it again, and, because I wasn’t near a university library at that time, had the article faxed to me from his office. Going through it carefully this time allowed me to grasp fully, for the first time, the unlikely-sounding truth that Africa’s megafauna, diverse as it still is, had been a great deal more diverse in the early Pleistocene: the 1.4 Ma extinction-event I mentioned in connection with the Schüle anecdote, saw the disappearance of an astonishing four elephant-like, or proboscidean genera, several other megaherbivores, and a number of big carnivores, including Africa’s saber, scimitar and dirk-tooth cats.

This revelation made sense to me. I had been puzzled, previously, by this question: if the Americas had been inhabited by seven elephant-like species before the arrival of humans,[6] then why wasn’t Africa, where the proboscidean order originated, home to as many, or, in fact, more kinds of elephant? What I was learning now gave me my answer: before the 1.4 Ma extinction spasm, Africa had been inhabited by no less than twelve proboscidean species.[7]

The 1.4 Ma extinction event had taken place, Paul noted, shortly after hominins had developed the larger, more complex and more diverse “Acheulean” or “mode two” toolkit. Paul also pointed out that the extinction had occurred at a time when there is no evidence of elevated faunal loss on any other land-mass including Madagascar, whose climate is closely tied to that of Africa. (The collapse of Madagascar’s megafauna would only happen, his argument continued, after humans arrived on that island some 1,700 years ago.)

* * *

I had the feeling, after reading and digesting Paul’s article, and chasing down its footnotes and references, that the first pieces of a puzzle might be falling into place. The African extinctions would have to be included, I decided, in the book I wanted to write about his overkill theory.

I was living in Vancouver, Canada, at the time, but I had a connection with the National Museum in Bloemfontein, South Africa, and its associated Florisbad Quaternary Research Station, through the work of my grandfather, T.F. Dreyer, who had been a professor of Zoology at the Free State University. Dreyer had discovered the partial skull of an archaic human he called Homo helmei at Florisbad in 1932.[8] The Florisbad skull was originally thought to be around 40,000 years old (which happened also to be the limit of the radiocarbon tests done on it). Judging by the fauna associated with it, though, Dreyer thought it was older than that, and, in 1996, it was indeed directly dated by ESR to 259,000 years bp through the efforts of its present curator, James Brink.[9]

When I arrived in Bloemfontein in 2000, I received a great deal of assistance from James, a paleontologist specializing in Pleistocene faunal turnover, and from Zoë Henderson, an archeologist also connected with the Florisbad station.

But I was still apprehensive about researching the African extinctions. Most paleoanthropologists would have regarded the idea that Early Pleistocene hominins could have wiped out big animals like deinotheriums and sabertooth cats as a patently absurd proposition, and many still do. How could those hominins have exterminated large animals, these sceptics might have asked, if they weren’t even able to hunt them in the first place? From about 1980 until the end of the 20th Century, it had, in Robin Dennell’s words, been “profoundly unfashionable”[10] to talk about big game hunting, or indeed any kind of hunting by members of the human family, before 40–50 thousand years ago. “Nowadays,” Ian Tattersall could still confidently inform the readers of his 1998 Becoming Human, “the notion of active, early human hunting of sizable mammals has largely been discarded…”[11]

Even Jared Diamond, who accepted[12] Paul’s insights into the end-Pleistocene and Holocene megafaunal extinctions, couldn’t stretch that acceptance to include the idea that members of the human family had been capable of causing extinctions earlier in the Pleistocene. He clung, instead, to the then-prevailing opinion that, before the “great leap forward” they were supposed to have made around forty thousand years ago, humans had been “little more than glorified baboons.”[13]

The material I was finding in the libraries of the Florisbad Research Station and the Universities of the Free State and the Witwatersrand, and discussing via email and phone calls with Paul, showed, however, that a very different picture of Early- and Middle Pleistocene hominins had begun to emerge in the the last years of the Twentieth Century. In 1995, carefully designed and shaped wooden javelins were discovered in an open-cast mine near Schöningen in North Germany,[14] in a 380,000-year-old Jagdlagerplatz or hunters’ cache. That cache yielded thousands of bone specimens, many marked by stone tools, representing mainly horses, but also red deer and bison. Between them, the Schöningen finds established clearly that “…early humans did not,” in the words of Hartmut Thieme, the principal investigator of the site, “rely mainly on carrion for their nourishment, as postulated in the last few decades, particularly by Anglo-American pre-historians, but that they were extremely accomplished hunters.”[15]

The “early humans didn’t hunt” dogma was, in fact, crumbling to an extent that wouldn’t have been thinkable a few years before: almost seven times older than the already-astounding Schöningen discovery, is a series of bones, unmistakeably marked by stone tools, which came to light in Ethiopia between 1997 and 2003.

The first part of this series (which is 2.6 to 2.5 million years old) was found at Bouri in that country’s Middle Awash region by an international team co-ordinated by Tim White.[16] The latest finds (dated to between 2.6 and 2.1 Ma), were made at Gona, some sixty miles north of Bouri, by a group which has included Sileshi Semaw and Manuel Domínguez-Rodrigo.[17]

One of the hominin-modified bones unearthed by White and his associates from Bouri’s 2.45–2.5 Ma Hata Member was the left lower jaw of a hartebeest-like antelope. Three successive, curved cutmarks made by a sharp stone flake toward the back of the inside of that jaw, inform us as clearly as a written account could, that hominins had cut out that animal’s tongue.[18]

The tibia of a “large bovid” found within 200 meters of the antelope jaw at the same stratigraphic horizon shows, on its surviving midshaft region, both cut- and chop marks, the latter presumably made for the purpose of removing marrow. The placement of cutmarks on the femur of a hipparion or three-toed horse, excavated within a meter of the bovid tibia fragment, indicates that the animal had been at least partially dismembered. Hominin-made modifications were also identified on bones (representing at least six different animals) found at the Gona sites. Dominguez-Rodrigo described those modifications as follows:

Most of the cutmarks on the Gona fauna possess obvious macroscopic (e.g. deep, V-shaped cross-sections) and microscopic (e.g. internal microstriations, Herzinian cones, shoulder effects) features, that allow us to identify them confidently as instances of tool-imparted damage caused by hominid butchery. In addition, the anatomical placement of the cutmarks on several of the recovered bone specimens suggests that Gona hominids eviscerated carcasses, and defleshed fully muscled upper and intermediate limb bones of ungulates – activity which further suggest that Late Pliocene hominids may have gained early access to large mammal carcasses.[19]

How did the beings who processed those carcasses get their “early access”? Very occasionally, they might have come across helpless or dead animals that had not yet been found by other predators or scavengers, but it’s hardly possible that they could have obtained all the carcasses and/or body parts represented by the Bouri and Gona finds in such lucky circumstances, and then have had the opportunity to butcher them without interference. It’s difficult, therefore, to resist the conclusion that “hunting and/or aggressive scavenging of large ungulate carcasses may,” in Domínguez-Rodrigo’s words, “have been part of the behavioral repertoire of hominids by c. 2.6–2.5 Ma….”[20]

It could not have been easy for those human-like beings to catch and kill adult antelopes. The Dutch settlers who landed on the Southern coast of Africa in 1652, were tantalized by an abundance of “elanden ende herten” (literally “elk and deer,” i.e. the antelopes Taurotragus oryx and, probably, Damaliscus sp.) grazing near their temporary fortification “outside cannon range,” but the commander of the settlement, Jan van Riebeeck, lamented that those animals were “too wild” to be approached within range of the would-be hunters’ arquebuses.[21] Fresh food was, at times, as critical for those Dutch settlers as it had been for the Pilgrims who had landed at Plymouth Harbour 32 years earlier, and Volume 1 of van Riebeeck’s diary, covering the first three years of his command, contains heartfelt wishes, and even prayers, for success in shooting or snaring one of those antelopes, but no mention of any success in that regard.[22]

Killing an adult antelope would not, therefore, be an easy matter for a modern human, unless he or she were equipped with more effective technology than arquebuses (or with the know-how of hunter-gatherers like the !Kung San). It’s astonishing, therefore, to be confronted with evidence showing that relatively small hominins with brains one-third the size of ours, repeatedly gained control over the carcasses of medium-sized and large herbivores more than two million years ago.

Disputing possession of such carcasses with other meat-eaters must at times have posed even bigger problems for those hominins than hunting itself: the scimitar-tooth cat Homotherium is included on a list of fauna whose remains were identified in the Bouri peninsula’s section of the Hata Member,[23] and it would continue to co-exist with hominins in Africa until it was extirpated from that continent in the 1.4 Ma extinction event.[24]

We don’t know yet know how long hominins had possessed the ability to butcher carcasses with stone tools when the Hata Member was laid down around the 2.5 Ma mark. The ability to “hunt and/or confront” suggested by the Bouri and Gona finds could not, in any event, have arisen overnight. We can surmise, therefore, that its possessors would have gained the ability to chase off small competitors like jackals, and medium-sized ones like cheetahs and hyenas of the striped and cursorial species,[25] well before they (or a successor hominin such as Homo ergaster/erectus) became able to confront Africa’s bigger cats, and the lion-sized Pachycrocuta hyena.[26]

* * *

None of the butchered animals represented at Gona and Bouri were bigger than the single “large bovid” identified at each of those localities. As we move a few hundred thousand years closer to the present, however, and cross the 2 Ma mark, the hominin-modified remains of much bigger animals ─ hippos, rhinoceroses and proboscideans ─ show up at Olduvai in Tanzania, and Koobi Fora in Kenya.[27]

Even viewed as a heuristic proposition ─ i.e. a hypothesis capable of throwing light on other questions before its own truth is considered proven ─ the development of an ability to hunt big herbivores and confront large competitors in the early Pleistocene offers an explanation for the otherwise unexplained and relatively abrupt increase in size involved in the evolution of Homo erectus/ergaster from its Australopithecine ancestor by about 1.7 Ma: while there was still a pressing need for the ancestors of erectus to be able to take refuge in trees from carnivores and megaherbivores, natural selection would have put a ceiling on their body weight. Size matters a great deal in the business of tree-climbing. Because leopards only weigh about one-third as much as lions do, trees provide them with a secure and dependable refuge from lions. Chimpanzees climb trees with what Jean Dorst and Pierre Dandelot call “consummate agility,”[28] while gorillas must, purely because of their larger size, climb with “great caution.”[29] If one of the hominin species was, after 2 Ma, developing increasingly effective methods of killing large prey and confronting large competitors, the pressure which had, for millions of years, restricted its chimpanzee-sized ancestors to their “tree-climbing” body-size would have been relieved, and in fact reversed, to produce the large and robust body of erectus.[30]

Acceptance of this early ability to “hunt and confront” is, of course, a sine qua non for the acceptance of Paul’s African overkill theory: hominins could hardly have been responsible for that overkill if they weren’t capable of killing in the first place. But proving that one or more of the Early Pleistocene hominins were hunters ─ even efficient hunters ─ would not, by itself, be enough to show that they were capable of exterminating their prey: Early Pleistocene Africa with its six big-cat species and its giant hyenas was replete, after all, with efficient four-legged hunters,[31] but none of them is suspected of causing the extinction of a significant number of the species they hunted or competed with.

To lend conviction, therefore, to the theory that the hominin tribe was responsible for the African extinctions that started with the 1.4 Ma event I’ve been referring to, one would have to show that at least one of its members was, in the millennia preceding that 1.4 Ma event, developing an extraordinary, and indeed disruptive, degree of ecological power.

The power of present-day Homo sapiens is clearly having a disruptive impact on the biosphere, and it seems clear, too, that this power is bound up, to a considerable degree, with the unprecedented level of our species’ intelligence.

How far back in our evolutionary history did this intelligence begin to surpass that of our prey, predators, and competitors? Intelligence does not, of course, fossilize, but it is closely bound up with inventiveness, and the archaeological finds at Bouri and Gona provide direct proof that at least one hominin species had, by the end of Pliocene, evolved a degree of inventiveness which already exceeded that of any non-hominin species.

Beings who can figure out how to fracture fine-grained rock in the right way to make sharp-edged cutters, don’t have to wait millions of years for “phylogenetic innovation,” i.e. natural selection, to give their species carnassial or meat-cutting teeth. Invention by individuals, i.e. “ontogenetic innovation,” can, in other words, produce useful innovations on a much faster schedule than the phylogenetic innovation which had, before the advent of human ingenuity set the pace for “arms races” between life forms in our biosphere.

…[M]ost species are locked in co-evolutionary, antagonistic relationships with prey, rivals, parasites, and predators, in which move and countermove take place slowly, over evolutionary time. Improvisation puts humans at a great advantage: Instead of being constrained to innovate only in phylogenetic time, they engage in ontogenetic ambushes against their antagonists – innovations that are too rapid with respect to evolutionary time for their antagonists to evolve defenses by natural selection. Armed with this advantage, hominids have exploded into new habitats, developed an astonishing diversity of subsistence and resource extraction methods, caused the extinction of many prey species in whatever environments they have penetrated, and generated an array of social systems far more extensive than that found in any other single species.[32]

Soon after hominin cranial capacity increased from the ~450 cc of Australopithecus garhi (the putative maker of the 2.6 Ma tools we’ve been talking about[33] ) to the 850 cc it reached with the advent of Homo erectus about 1.8 Ma, the earliest Acheulean tools discovered to date show up in the Kokiselei 4 site in West Turkana’s Nachukui formation.[34]

The Acheulean or “Mode 2” toolkit was larger and more diverse than its Mode 1 predecessor, and was used for purposes as disparate as digging, butchery, woodwork and the scything of soft plant material.[35]

The control and use of fire may also have predated the 1.4 Ma African extinction event. Strong evidence that erectus was using fire by 1 Ma in South Africa’s Wonderwerk Cave has recently been presented in PNAS,[36] but this capability may, as we’ll see, have emerged before that date.

Evidence of fire-use found in Member 3 at Swartkrans,[37] some 340 miles north-east of the Wonderwerk site, appears to be up to half a million years older than the Wonderwerk material. That evidence consists of 270 burned bones, 13 of them cut-marked, 47% of them decarbonised to a greyish-white color by the relatively high temperatures generated in “tended” fires. These bones were found throughout the six-meter profile of Swartkrans’ Member 3, indicating repeated fire-use over a period of some thousands of years.[38]

Compared to the relatively “readable” strata deposited in East Africa’s Rift Valley, interleaved with securely-datable layers of volcanic ash, the breccia in South Africa’s limestone caves (deposited by chaotic events like cave-ins and talus slides) is notoriously difficult to date. However, the presence in each of Swartkrans’ near-contemporaneous older Members (1, 2 and 3) of at least one of the genera which disappeared from Africa in the 1.4 Ma extinction event[39] we’ve been talking about, makes it hard to escape the conclusion that the fire-use evidenced in Member 3 was taking place before that extinction episode.

A 2003 review of the fauna of Swartkrans’ Members 1–3 by Darryl de Ruiter yielded an estimate of 1.6 Ma for Member 1, which was very close to the result produced by an earlier study by Elizabeth Vrba of Member 1’s “Hanging Remnant.”[40] De Ruiter’s comparison of the faunal assemblages from the Hanging Remnant with Members 2 and 3, suggests that there is little difference in the faunal composition of the three Members. A combination of ESR and U-series data was used by other investigators to calculate open system ages for Member 1′s Hanging Remnant, which yielded a “best estimate” mean value 1.63 Ma.[41]

In his 2003 faunal review, de Ruiter had, however, concluded that Members 2 and 3 were contaminated to some degree by recent material. The fact that the 270 burned bones in question were distributed, alone or in small assemblages, throughout Member 3’s six-meter profile, makes it highly unlikely that they could all be intrusive specimens, but it remains that Swartkrans has not produced the conclusive, in situ evidence for hominin fire-control claimed for the Wonderwerk site.

The Swartkrans evidence remains, nevertheless, a highly persuasive indication that hominins may have begun to control fire before the 1.4 Ma African extinction event. The evidence for Early Pleistocene fire control at FxJj 20 Main, near Koobi Fora,[42] some three and a half thousand kilometers north of Swartkrans, could also be placed in a “strong but not conclusive” category.

Brian Ludwig’s finding that signs of thermal alteration start showing up after 1.6 Ma, in a small but consistent percentage of silaceous hominin-modified stone in nearly fifty sites in both the Olduvai and Turkana basins,[43] is also consistent with the idea that a hominin ─ presumably Homo erectus ─ learned to control fire soon after the Acheulean tool-kit was developed.

The nutritional and anatomical evidence that erectus became able to control fire shortly after 2 Ma marshalled by Richard Wrangham in his 2009 Catching Fire: How Cooking Made Us Human, is indirect and circumstantial, but no less perceptive and plausible on that account.

* * *

The discovery of fire-use, “probably the greatest,” as Darwin saw it, “ever made by man, excepting language,”[44] would have brought immense benefits to its possessors. Its ability to neutralize bacteria and toxins and release nutrients would have brought about a big expansion of the food base. Fire could also have been used to drive prey animals, and, in some circumstances, to kill them. It would also have enabled its discoverers to repel predators, drive them off their kills, and reveal their presence at night. Bob Brain suggests that the discovery of fire-use could have been a decisive factor in tipping the balance of power away from Africa’s large predators in favor of erectus. “The tipping of this balance,” Brain wrote in his Hunters or the Hunted, “represented, I think, a crucial step in the progressive manipulation of nature that has been so characteristic of the subsequent course of human affairs.”[45]

Profound as its impact must have been, though, this discovery was simply another manifestation of the mental illumination which was allowing erectus to increase its ecological power so rapidly in the Early and Middle Pleistocene.

* * *

That rapid increase took the early-Pleistocene megafauna by surprise. Pliocene and Early Pleistocene megaherbivores would not, Wilhelm Schüle reasoned, have been equipped with the instinctive aversion to our species exhibited by Africa’s surviving megafauna, nor with the exceptional intelligence of the surviving elephant species.[46]

The fact that the great majority of the twenty-odd proboscidean species that were in existence at the beginning of the Pleistocene have become extinct should not, therefore, be a surprising one. It’s surprising, on the contrary, that two of those species, Loxodonta africana and Elephas maximus, have survived into the present. Their survival tells us that the avalanche of hominin ingenuity which overwhelmed the planet’s other proboscideans had started slowly enough in the regions occupied by hominins before the 1.4 Ma extinction event, (i.e. Africa and South Asia) that phylogenetic innovation had enough time to stay ahead of it by evolving the extraordinary degree of intelligence those two species possess today.

By the time Loxodonta and Elephas were subjected to the relatively fast surge in our species’ power which took place near the end of the Pleistocene, ─ the surge that killed off all the proboscidean species that inhabited Northern Eurasia and the New World ─ those two survivors were behaviorally equipped by their early-Pleistocene trials with our family, and by more than a million years of subsequent conflict and co-evolution with that family, to withstand it.

* * *

When Paul was researching his African overkill article in the early sixties, radiocarbon testing could date organic material 40,000 years into the past, but no further. At that time, uranium series analysis could, on the other hand, only accurately date material older than several millions of years. The chronology of the intervening period was shrouded in ignorance, and it was generally assumed that the Pleistocene didn’t span much more than 500,000 years.

It was against that background that Paul initially estimated,[47] before publishing a corrected chronology,[48] that the African extinctions he was writing about started up a hundred thousand years ago or less.

In 1961 Garniss Curtis and Jack Evernden had created a stir in the scientific world by using their newly-perfected potassium/argon test to date Olduvai Gorge’s Early-Pleistocene Bed 1 to 1.75 Ma,[49] setting in motion the creation of the first reliable paleontological and geological chronology for Pleistocene Africa. That process had not, however, made much progress when Africa and Pleistocene Overkill appeared.

Paul was able to focus, nevertheless, on the salient facts that the African extinctions took place (a) after the development of the Acheulean industry, and (b) tens of thousands of years before the end-Pleistocene American faunal collapse (and an even longer time, therefore, before the Holocene collapse of Madagascar’s megafauna).

The asynchronous nature of these three extinction episodes, the coincidence of the American episode (but not the other two) with the extreme climatic swings that took place at the end of the Pleistocene, and the fact that the impacts of the three episodes ranged from moderate in Africa through severe in North America to extremely severe in Madagascar ─ all sound assumptions ─ formed the basic framework on which Paul built his arguments.

The logic of those arguments is (from my admittedly partisan point of view) so cogent and consistent, that the world-wide overkill scenario could appear, with benefit of hindsight, to have been a more obvious conclusion than it was. In reality, of course, it took a penetrating intellect, a developed intuition and a good measure of courage to discern and elucidate its truth.

That truth has not yet been universally recognized. Mike Archer, (to select only one of its many opponents) a Professor at the School of Biological, Earth and Environmental Sciences at the University of New South Wales, finds it difficult to understand, for instance, why anyone would “even assume” that the ancestors of Australia’s Aborigines were responsible for the extinction of that island-continent’s megafauna. “When you look at Australian indigenous peoples today,” he argues, “they are among the most noble, most responsible managers of sustainable harvesting programs in Australia.”[50]

The noble savage doctrine still enjoys what Steven Pinker calls “a sacred status in modern intellectual life.”[51] Its pervasive influence can even prevent people who are sympathetic to Paul’s insights from fully comprehending them: characterizing Paul’s overkill scenario as “a fairly good theory,” recently, one commentator explained, for instance, that “…it is possible that human beings, when they enter a new land may just not have a clue as to how to maintain sustainability until they’ve been there for a while.”[52]

That statement might sound unexceptionable on first reading, but let’s step back for a moment and ask ourselves whether North America’s surviving megafauna ─ bears, bison, moose and elk ─ really owe their continued existence to the fact that the continent’s first human inhabitants had learned (or relearned), after they had “been here for a while,” to “maintain sustainability.” Paul’s own answer to that question was an emphatic “no”: in his 1999 War Zones and Game Sinks in Lewis and Clark’s West, he and his co-author Christine Szuter argued compellingly that the impact of American Indian hunting was limited by warfare and disease rather than the exercise of any supposed restraint on the part of the hunters.[53]

The first humans to arrive in Australia and the New World never acted, in short, as protectors of the natural world. But these “aboriginal” peoples were not driven, either, by inordinate levels of greed or cruelty to wipe out the diprotodons and mammoths they encountered. Paul’s insights suggest, instead, that it was simply the unparalleled level of intelligence of our species which made those exterminations possible and, indeed, perhaps inevitable. “Humans,” Richard Dawkins said in a 2001 speech to the Foundation for Democracy and Sustainable Development, “are no worse than the rest of the animal kingdom. We are no more selfish than any other animals, just rather more effective in our selfishness and therefore more devastating.”[54]

* * *

Some of the earlier research for my book on Paul’s theory was done in the Stevenson-Hamilton Memorial Library in Skukuza, in South Africa’s Kruger National Park. At that time, I was more optimistic about my species’ prospect of stopping the extinction it’s causing than I am today.

Aside from the fact that Kruger is a wildlife park in the usual sense of that word, it is also a remarkably successful example of the rewilding that Paul championed in the later part of his career.[55] Of the four biggest animals which had lived in the area presently covered by Kruger up until about 1880, (elephant, hippo, white rhino and black rhino) only hippos survived in viable numbers by the beginning of the Twentieth Century. Elephants still entered the Park’s remote northern end from time to time, and black rhinoceros individuals wandered in from Mozambique up until the forties, but white rhinoceroses had disappeared from the entire area, and were thought to be extinct as a species.

White Rhinos: What Can I Say?Then an isolated surviving population of white rhinos, probably numbering less than 100, were discovered about a hundred miles south of Kruger. The drama of their last-minute protection, population restoration, and eventual re-introduction into Kruger took place over the century following that discovery. By the time I was working on my book in the Skukuza research camp in 2000, Kruger ─ which is about the size of Israel ─ had become one of the last places in Africa where Africa’s two rhinoceros species were present in numbers large enough to ensure their continued viability. Paul was enthusiastic about what he referred to as the “resurrection” of the white rhino. I was enthralled, for my part, by the months I spent in Kruger, surrounded on every side by evidence of how people could undo the damage they had done to wilderness and wildlife, and wrote the first few chapters of my book in that buoyant spirit.

Elsewhere, unfortunately, biodiversity was still in full retreat. Although large animals represented only a tiny fraction of the species that were being lost, some of them, too, were being pushed into oblivion. Between the time I started working on the book and today, the Sunda rhinoceros disappeared from Vietnam, leaving that species represented only by the flickering candle of a small, vulnerable population in Java. Since that time, too, the Northern White Rhinoceros has crossed the line into functional extinction, and twenty-five million years of unique evolution were undone when the “Goddess of the Yangze,” the Baiji dolphin, succumbed to human activities.[56] Also in that time, the Sumatran rhinoceros and a dozen other mammalian species, from the Somali wild ass with its elegant striped legs, to the poorly-known hirola antelope, declined to the point where they are poised to follow.

As I dreamed my dreams of ecological salvation back there in the Skukuza research camp in the year 2000, I did not suspect, either, that a poaching war was soon to start in the Kruger Park itself, which would kill hundreds of rhinos per year, rapidly reversing the rewilding miracle I was enthusing about to Paul.[57]

* * *

In the late Nineties, shortly after poaching had wiped out East Africa’s rhinos but before the scourge had spread to South Africa, I noticed the outline of a rhinoceros traced onto a small square of cardboard discretely tucked into the corner of the window of a store in Vancouver which sells Chinese traditional medicines.

I felt uncomfortable about the fact that I did nothing about that sign, and was reminded of my inaction recently when I walked past another store on the corner of East 41st Avenue and Victoria Drive here in Vancouver, that was selling gecko skins and dried fishes in the seahorse-pipefish family.

Populations of both Tokay geckos and the syngnathid fishes are under pressure[58] because of their supposed curative powers, and so, despite the fact that their sale here in Canada might, for all I know, be permissible from a legal point of view, I thought I should at least take a picture of these animals. Walking into the store, I barely had time to point my phone camera, before the owners advanced on me with a chorus of “no picture” admonitions. I managed two shots ─ my closest-ever approach, I thought wryly, to environmental activism ─ before I was hustled out:

Dried Engangered Geckos

I have to remind myself, before I start feeling too self-righteous about the trade in endangered wildlife, that it took me far too long to stop ordering tuna sushi. (“What difference,” my rationalizing mind would ask “will this little gesture on my part make?”) More importantly, my own efforts to survive and reproduce, supported by a bountiful economic system, an increasing degree of peace among humans themselves, and sophisticated medical know-how, have made me a full participant in a human expansion which has increased my species’ population three-fold during my lifetime, thrusting hundreds of thousands of other life-forms aside.

*  *  *

I’ve devoted so much space in this article to matters related to the archaeology of Plio-Pleistocene Africa, that it might have seemed that I was, at times, straying off the  topic of Paul’s insights. But it is, as I’ve tried to show, precisely those archaeological discoveries — most of them made more than thirty years after Paul’s Africa and Pleistocene Overkill article appeared in 1966 — that have helped to transform his idea of hominin overkill in the earlier Pleistocene from a largely ignored and, indeed, barely conceivable notion, to one which is starting to receive serious academic attention.[59]

The long delay between the appearance of Paul’s 1966 article and the acceptance of his global overkill theory (which still has not, of course, taken place) is comparable, in some ways, to the half-century delay between the 1915 appearance of Alfred Wegener’s book on continental drift and the final acceptance of that notion in the 1960s.

The main reason for the delay in Wegener’s case appears to have been his inability to identify the force driving the “shifting” he was arguing for. Even after Arthur Holmes correctly identified that force in the 1920s, as convection cells in the earth’s magma created by radioactive heating, the scientific community wanted the details of this mechanism spelled out for them before they would accept the idea of moving continents. It was, therefore, only after the phenomenon of sea-floor spreading and subduction had been fully elucidated in the early nineteen-sixties, that Wegener was finally vindicated.

So what, one might ask, is holding up the full acceptance of Paul’s insights? What essential element of  that theory remains undiscovered and undescribed?

Paul’s insights will undoubtfully be fleshed out with plenty of new facts and details in the coming decades, and some of his conclusions may well be modified in the process,[60] but I do not expect that any of the essential elements of his overkill theory will be called into question. Like John Alroy I believe that the overkill hypothesis has “already… been ‘proven’ as thoroughly as any historical hypothesis can be.”[61]

All of the key evidence was available years ago, and all of it firmly refutes competing, ecologically-oriented hypotheses. The event’s timing, rapidity, selectivity and geographic pattern all make good sense according to the anthropogenic model, and no sense at all otherwise. To my eyes, this assessment is so clear that further “tests” are not really necessary.

No intellectually respectable objections are raised, nowadays, against the proposition that the arrival of our species on New Zealand during or near the 13th century AD[62] was the cause of the disappearance, within a few centuries after that arrival, of New Zealand’s avian megafauna. The approximately 38 bird species that were swept away by the first wave of human settlement on those islands included the world’s largest eagle, nine species of moa, the largest of which stood more than 10 feet tall, and two unique “adze-bill” predator/omnivores.[63]

Nor does any scientific doubt remain that the combination of human predation, human-caused habitat alteration, and human-introduced species which caused the New Zealand collapse, caused similarly sudden and catastrophic species-losses on Madagascar and on the Hawaiian Archipelago[64] after humans reached those islands some five hundred years before their arrival on New Zealand.

Astonishingly, however, the clear and undisputed fact that these Early Medieval megafaunal collapses were caused by humans, has not been used as a “Rosetta Stone” to decipher to the general satisfaction the meaning of the similarly catastrophic losses of megafauna which took place earlier in the Holocene and in the late Pleistocene; losses which took place on all the islands[65]  ─ and indeed all the regions and continents ─ which were (like New Zealand, Madagascar, and Hawaii) being settled for the first time by the genus Homo.

All scientific paradigm shifts are disconcerting and uncomfortable to one degree or another. Wegener’s theory itself provoked bitter resistance, involving personal ridicule as well as threats to careers and to funding. Paul’s insights touch, however, on issues which are even more unsettling than the geomorphological truths Wegener was urging upon the scientific community: the global overkill theory implies a great many controversial things about the evolutionary history of our own species, and human evolution is a notoriously emotive subject in its own right. Paul’s insights bear directly, moreover, on the even more fraught issue of the enormous human-caused extinction our planet is presently undergoing. What effect would Paul’s new ecological history have on our attitude toward that extinction? What would result, for instance, from its collision with the ideas of someone like the Canadian environmentalist David Suzuki who believes humans can stop exterminating other species by re-establishing the “sacred balance”[66] that “pre-industrial” or “indigenous” peoples are thought to have maintained with the natural world?

Paul’s insights need not, in my opinion, replace the Rousseauian myths propagated by those who share Suzuki’s beliefs with a Hobbesian caricature of a species burdened by an aberrant level of cruelty and aggression. Humans beings — subject as they unquestionably are to the normal complement of mammalian drives — clearly do a great many things which fall foursquare into our conceptions of “cruelty” or “aggression,” but the exceptional intelligence which makes humans so much more destructive than other animals, also allows them to experience something that is literally inconceivable for other animals: concern for the survival of other species.

While I was writing this, the BBC ran an item about the survivor of an attack by a great white shark, who now campaigns for the protection of the species that nearly caused his death.[67] It’s unthinkable, of course, that a baboon which has survived an attack by a leopard, could be motivated by that attack to make efforts to protect leopards. It is only “man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends… to the humblest living creature,”[68] that could react in such a biologically anomalous way.

“Save the whales” became something of a joke among those who deride “tree huggers,” but it is momentous, of course, rather than funny that Homo sapiens has developed enough understanding to step back from the edge of wiping out the planet’s very largest megafauna.

Human erosion of the biosphere has, however, gone far beyond the overkill of large species. It has developed via agriculture — i.e. the elimination of unwanted life-forms on given tracts of land to create monocultures — into a great many other diversity-threatening activities. These include wholesale habitat destruction, the witting and unwitting introduction of alien species, and the alteration of oceanic and atmospheric chemistry by mining nitrogen from the air and fossil fuels from the earth. With the best will in the world, we may simply not be able to identify and ward off enough of the “thousand cuts” by which biodiversity is dying. It’s by no means impossible, therefore, that the anthropogenic extinction-spasm could continue, despite our best efforts, to the point where it degrades the biosphere’s ability to provide us with food, clean water and air.

* * *

The German word for despair is Verzweiflung. Maybe because it’s got Zweifel, “doubt,” as its root, it feels like the best label for the of the blend of perplexity and dismay I used to feel, before my exposure to Paul’s thinking, about the rising tide of extinctions my species is causing.

Paul’s insights didn’t lessen the dismay part of my Verzweiflung, but they did clear up some of the perplexity. On the most simplistic and emotional of levels, they brought me to the realization that my species wasn’t “bad” or “unnatural.” Homo sapiens has unquestionably had a tragic impact on the biosphere, but it, and the devastating level of its intelligence, are no less products of nature — of natural selection — than the coral-reef communities and rainforests whose existence it is currently threatening.

In order to survive on the Pliocene veld two and a half million years ago, our ancestors had to defend themselves against and compete with a formidable suite of big predators. The outcome of that struggle was by no means assured: the only weapon those hominins possessed to counter the all-too-tangible teeth, claws and horns of their antagonists was an abstract and rudimentary ability to think up useful new devices and behaviors. Today we are involved in another struggle with an uncertain outcome: to prevent that ability from making the earth unlivable for other organisms, and, indeed, for ourselves.

The only weapon available to us in this latter-day struggle is, ironically, the same one that enabled our destructiveness in the first place: the power of the human brain. But that brain cannot, of course, come to grips with the forbidding complexities of this problem if it’s not in possession of the relevant information.

The real facts of our species’ ecological history are an indispensable part of that information, and nobody has done more to make them available to us than Paul Martin.

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Footnotes

  1. Jensen September 16, 2010. University of Arizona News.  http://www.uanews.org/story/paul-s-martin-pleistocene-extinctions-expert-dies ^
  2. Schüle 1990a, p. 2001. ^
  3. Schüle 1990b, p. 2005. ^
  4. Martin 1996, p. 342. ^
  5. Martin 1996. ^
  6. Kurtén 1980, 343–354; Prado 1999. ^
  7. Coppens 1978, p. 367; Haltenorth 1980, pp. 19–22. ^
  8. Dreyer 1935. ^
  9. Grün 1996, p. 501. ^
  10. Dennell 1997, p. 767. ^
  11. Tattersall 1998, p. 131. ^
  12. Diamond 1991. ^
  13. Diamond 2008, p. 21. ^
  14. Thieme 1997, p. 807. ^
  15. The quotation is my translation of the following passage in Thieme 1998, p. 47: “…daß der Urmensch… seiner Ernährung nicht, wie in den vergangenen Jahrzehnten besonders von anglo-amerikanischen Prähistoriken postuliert, überwiegend durch das Erbeuten von Aas gesichert had, sondern ein äußert geschickter Jäger war.” ^
  16. de Heinzelen 1999, pp. 625–629. ^
  17. Domínguez-Rodrigo 2005, pp. 109–121. ^
  18. See Fig. B, in de Heinzelen 1999, p. 628. ^
  19. Domínguez-Rodrigo 2005, p. 109. ^
  20. Domínguez-Rodrigo 2005, pp. 109–110. ^
  21. Bosman 1952, p. 52. ^
  22. The settlers were able to shoot a hippopotamus, a rhinoceros and an aggressive lion in the first three years of van Riebeek’s command, but the only references to antelopes I found in Volume 1 of his Cape diary were repeated complaints of the kind that “men se niet genaeken can” – “one cannot lay a hand on them.” ^
  23. Table 1, de Heinzelen 1999, p. 627.  The fact that no other big cats, and no hyenas, appear in the Hata faunal record does not of course, mean that such animals were absent from the area at the time when Hata Member was being laid down. It is in fact hard to imagine that none of Africa’s other big, Early-Pleistocene predators would have been present at that time. ^
  24. Lewis 2007, p. 90. ^
  25. Edmeades 2006, http://www.megafauna.com/chapter10 ^
  26. When I originally formulated these thoughts on the trajectory that the development of hominin competitive power might have followed, I was hesitant about in including them in my book, because I thought they would (along with the entire notion of hominins diminishing Africa’s megafauna in the early Pleistocene) be dismissed as too speculative to the taken seriously. Even as I was overcoming these misgivings to write and upload those thoughts in 2006, however, the unthinkable was already in the process of becoming thinkable. Reasoning independently of Paul’s work, on the basis of an intensive study of the origination and extinction of African carnivores during the late Pliocene and early Pleistocene, Margaret Lewis and Lars Werdelin came to the following conclusion in 2007:

    …Although hominins were unlikely to have been top predators upon first entrance into the carnivore guild, effective anti-predator/anti-kleptoparasitism strategies in combination with the eventual evolution of active hunting would have increased the rank of hominin species within the guild. While the appearance of stone tools at 2.6 Ma has no apparent effect upon carnivorans, the appearance of Homo ergaster after 1.8 Ma may have been at least partly responsible for the decrease in the carnivoran origination rate and the increase in the extinction rate at this time. The behavior of  H. ergaster, climate change, and concomitant changes in prey species richness may have caused carnivoran species richness to drop precipitously after 1.5 Ma. In this situation, even effective kleptoparasitism by H. ergaster may have been enough to drive local populations of carnivorans that overlapped with hominins in dietary resources to extinction.

    Lewis 2007, p. 77. ^

  27. For Olduvai, see Leakey, M. 1971. (Deinotherium butchery p. 285. Stone tools associated with Elephas recki p. 64, and with the extinct buffalo Pelorovis, p. xix.) With regard to Koobi Fora, see Braun 2010, p. 10004. (cutmarked rib of a rhinocerotid and the astragulus bone of a hippopotamus, the latter cutmarked in a manner consistent with disarticulation.) ^
  28. Dorst 1970, p. 89. ^
  29. Dorst 1970, p. 87. ^
  30. Edmeades 2006, Chapter 9. ^
  31. Coppens 1978. p. 367; Haltenorth, T., 1980, pp. 19–22; Edmeades 2006, Chapter 12. ^
  32. Cosmides 2000, p. 53. ^
  33. Asfaw 1999; de Heinzelen 1999. ^
  34. Lepre 2011. ^
  35. Keeley 1981; Domínguez-Rodrigo, 2001. ^
  36. Berna 2012. ^
  37. Brain 1998 and 2004a. ^
  38. Brain 2004b. ^
  39. Member 1 yielded two specimens of the cursorial hyena Chasmaporthetes that became extinct in Africa about 1.5 Mya, and a large, indeterminate canid which has not shown up in later deposits, possibly allied or conspecific with Canis lycaonoides. (See on the latter point Lewis 2007.)
    Member 2 contained two specimens of Chasmaporthetes, and one of the large canine mentioned above.
    Member 3 (in which the burned bones were found) yielded one specimen of the sabertooth cat Megantereon, and two of Chasmaporthetes.<br />See de Ruiter, D., 2003 and 2004; Watson 2004. ^
  40. Vrba 1982. ^
  41. Curnoe 2001. ^
  42. Bellomo 1994; Rowlett 2000. ^
  43. Ludwig 2000. ^
  44. Darwin 1871, p. 132. ^
  45. Brain 1981, p. 273. ^
  46. Schüle 1990 b and 2000. ^
  47. Martin 1966, p. 341, Fig. 1. ^
  48. Martin 1984. ^
  49. Leakey, L., 1961. ^
  50. Megafauna Extinction. The Science Show, ABC Radio National. http://www.abc.net.au/radionational/programs/scienceshow/megafauna-extinction/3489156.  Broadcast:Saturday 8 September 2001 12:10PM. ^
  51. Pinker 2002, 6. ^
  52. http://www.youtube.com/watch?v=3atnfKzObaM: YouTube video (uploaded Jan 21, 2012) at 21 minutes, 49 seconds, and at 22 minutes, 08 seconds.
    The writer John Frederick Walker is also of the opinion that, if humans restricted themselves to killing only enough mammoths to feed themselves, they could not have exterminated the species. A small human population could not, he thinks, have exterminated America’s mammoths unless they “knocked off more than they could eat, just for the hell of it.” (http://johnfrederickwalker.com/tag/christoper-johnson/)
    A population of 50 human immigrants, sustained by a plentiful supply of naïve, easy-to-hunt animals like tortoises and glyptodonts, would, however, increase. And even if that increase only amounted to a modest 2% per annum, it would produce 5,000,000 people in only 581.384 years. It’s more likely, however, that the first Americans would have experienced a larger annual increase: at 4% p.a., a rate equaled by several contemporary populations, 50 immigrants would take just under 294 years to reach the 5,000,000 mark. ^
  53. Martin 1999. ^
  54. Dawkins 2001. PDF, p. 8. ^
  55. For an account of how decimated species were restored in the Kruger Park, and locally extinct ones reintroduced, see Edmeades 2006. http://www.megafauna.com/chapter2.htm, and http://www.megafauna.com/chapter3.htm. ^
  56. Farewell to the Baiji, http://www.chinadialogue.net/article/show/single/en/673-Farewell-to-the-baiji Retrieved 8/27/2012. ^
  57. The rhino has been named South Africa’s newsmaker for 2012, based on the extensive media coverage around the slaughter of the creature for its horn: http://www.theaustralian.com.au/news/breaking-news/rhino-named-s-africa-newsmaker-of-2012/story-fn3dxix6-1226557476673
    Business Day Live article by Sue Blaine, 1/11/2013.
    http://www.bdlive.co.za/national/science/2013/01/11/rise-in-rhino-poaching-threatens-to-undo-years-of-successful-effort ^

  58. Geckos: http://globalvoicesonline.org/2011/08/17/philippines-tokay-gecko-hunting-craze/ http://www.boddunan.com/articles/science-nature/70-nature/20713-tokay-gecko-the-reptile-endangered-by-myths.html

    Syngnathid fishes: http://www.endangeredspecieshandbook.org/trade_traditional_seahorses.php

    http://www.care2.com/causes/over-16000-dried-seahorses-seized-by-peruvian-police.html ^

  59. See for example Waguespack 2005. ^
  60. I’ve never been comfortable, for instance, with the idea that the first humans to enter the Americas wiped out the extinct megafauna of those continents in a “blitzkrieg” that was completed in the space of a single millennium.  Madagascar has a land area smaller than that of Texas, and yet a study by David Burney and his colleagues (Burney 2004) showed that the that the great majority of Madagascar’s extinct megafauna was still in existence 1,300 years after humans first arrived on that island, and that several of the island’s large extinct lemurs survived until at least 1,800 after that arrival. I venture to suggest, therefore, that research could show, in the coming years, that Homo sapiens took well over two millennia to complete the end-Pleistocene exterminations that took place in the Americas. ^
  61. Alroy 1999, p. 105. I have to mention that Alroy’s remarks were directed at the North American overkill. ^
  62. Wilmshurst 2008. ^
  63. Flannery 1994. ^
  64. James 1987. ^
  65. Duncan 2013. ^
  66. Suzuki 1999. ^
  67. Shark attack survivor campaigns to save great whites. BBC News, March 10, 2013. http://www.bbc.co.uk/news/magazine-21719781. ^
  68. Darwin 1871, p. 406. ^