Balboa Park was repurposed after the closure of the exposition and now hosts seventeen museums and cultural institutions, among which The Nat stands out for its excellent collections and for its research expertise. As Santha and I strolled toward it on a bright Southern California morning, we couldn’t help but reflect on the irony. In a museum in a park named after an arriviste European adventurer, we were about to be shown evidence that might speak to the truly vast antiquity of Native Americans in the lands that Europeans had stolen from them with fire and sword.
Rebecca Handelsman had asked us to meet her at The Nat’s south entrance but we were early so we spent some time in the north atrium first, which is dominated by a looming skeleton cast of an Allosaur, a predatory dinosaur a bit like its more famous younger cousin Tyrannosaurus rex.
Scientists now agree that T. rex and the entire nonavian Dinosauria clade became extinct virtually overnight after a large asteroid or comet—more likely the latter2—hit the Gulf of Mexico around 65 million years ago. There is also no doubt that it was this sudden and cataclysmic eradication of dinosaurs from the planet that opened the way for the rapid, uncontested expansion into new niches of the hitherto-insignificant mammalian line. We humans today are among the descendants of those early mammals.
It’s thought-provoking, isn’t it, that cosmic impacts, whether by asteroids or by comets, can sometimes be of such magnitude that they drastically redirect the evolutionary path of life on earth. It has happened more than once, as we shall see. However, a cataclysm was not to blame 130,000 years ago when a lone mastodon, perhaps old or sick, died on a floodplain in Southern California and was subsequently scavenged, with the carcass then quite rapidly covered by, and entombed in, a deposit of silty, sandy, fine-grained sediment.3 There it remained undisturbed until November 1992, when the California Department of Transportation undertook highway construction on State Route 54 where San Diego borders National City.4 It was routine practice for paleontologists from The Nat to monitor road-grading in Southern California in case any important fossil material was exposed, and Richard Cerutti, the monitor on duty at SR 54, spotted the fossilized bones and the tusk of what he at first thought was a mammoth.5 He halted construction in the immediate vicinity until a proper excavation could be undertaken, and called in his boss, Dr. Tom Deméré, to lead it.6
Working together with a team of other researchers from The Nat, Cerutti and Deméré very quickly established that the fossilized remains, including many bones, both tusks, and several of the animal’s teeth, belonged to a mastodon.7 Like the mammoths, to which they were closely related, mastodons were swept from the face of the earth in the sudden and mysterious extinction of America’s Ice Age megafauna that took place around 12,800 years ago8—the same epoch exactly that saw the equally abrupt and equally mysterious disappearance of the Clovis culture.
From quite early on both Cerutti—after whom the site is now named—and Deméré were intrigued by what the excavation revealed: “Many of the bones were strangely fractured—or missing entirely. And there were several large stones, found in the same sediment layer as the bones and teeth, that appeared out of place. It looked like an archaeological site—like the preserved evidence of human activity.”9
As well as the hefty rocks, unusual in fine-grained sediment, smaller pieces of sharply broken stone were found peppered throughout the Cerutti Mastodon Site: “This is not typically something you would see as a result of normal geological processes. The combination of stones … together with broken bones was interesting and instigated speculation regarding the possibility of human activity at the site.”10
At first intriguing, the implications of the data grew worrying when it began to become obvious that the site was extremely ancient, lying embedded in sediments “that had been deposited much earlier, during a period long before humans were thought to have arrived on the continent.”11 In the early 1990s, radiometric techniques capable of peering much further back into the past than the standard 50,000-year limit for carbon dating12 were already available. Unfortunately, however, they had not yet attained sufficient accuracy to give scientists a high level of confidence in the age range suspected for the Cerutti Mastodon Site.13
The end result, after key finds were moved to The Nat where they were housed in the archives, was that the site was reburied and abandoned. Despite its anomalous character and suspected importance, it was just too explosive to put before the scrutiny of hostile archaeologists while the dates remained uncertain. “If you claim something is that old you get blasted,” Cerutti said, referring to the Clovis First lobby, “which is why some archaeologists stopped working on sites like this. They didn’t want to get blasted.”14
It wasn’t that the Cerutti Mastodon Site was completely forgotten in the 25 years after the excavation stopped. It’s on record that Tom Deméré invited several other researchers to study the collection of key finds kept at The Nat, but none did so.15
Robson Bonnichsen, founder of the Center for the Study of the First Americans, warned him that “research that contributes to First American Studies is a game of hardball.”16
Months ran into years with no journal article on the site even drafted, let alone published, nor any further investigation undertaken. Cerutti, reportedly, was so disappointed that he stopped going anywhere near State Route 54.17 The whole exciting matter seemed to have fallen into stagnation.
It was not until 2014, more than two decades after the mastodon’s discovery, that the tide decisively turned.18 Built on improved understanding of processes that incorporate natural uranium and its decay products in fossil bone, a newly enhanced technique, known as 230 Th/U radiometric dating, was now available that could settle the age of the Cerutti deposit once and for all. Deméré therefore sent several of the mastodon bones to the US Geological Survey in Colorado, where geologist Jim Paces, using the updated and refined technique, established beyond reasonable doubt that the bones were buried 130,000 years ago.19
Now things began to move much more swiftly and it was time to reexamine the strange fractures on some of the bones that had been noticed back in 1992 and also to take a much closer look at the “out of place” stones and rocks found in the same sediment layer. To this end the large and eclectic team of investigators who would eventually coauthor the landmark 2017 paper in Nature had already begun to form. Tom Deméré and Richard Cerutti were at the heart of it but other members included Dr. Steve Holen, curator of archaeology at the Denver Museum of Nature and Science, a specialist in the ancient uses of bone, Professor Daniel Fisher of the Department of Earth and Environmental Sciences, University of Michigan, Dr. Richard Fullagar of the Centre for Archaeological Science, University of Wollongong, and Dr. James Paces, Research Geologist at the US Geological Survey.20
It was a formidable team, their work was meticulous, and publication of the paper in Nature meant that archaeologists, just then cautiously emerging from the shadow of the Clovis First paradigm and adjusting themselves with difficulty to ages in the few tens of thousands of years for sites like Monte Verde, Meadowcroft, and Bluefish Caves, were now obliged to contemplate a site dating back to the Eemian, the last interglacial period that extended from roughly 140,000 years ago down to about 120,000 years ago when the Pleistocene ice sheets began to expand again.21
At that point in 2017 it was still believed—though new evidence would soon substantially change the picture22—that anatomically modern humans had not even left their African homeland 140,000 years ago.
So how could they possibly have gotten to America before they’d even set out on the epic migrations by which they populated the world?
Having researched the Clovis First wars, and indeed the whole story of prehistoric archaeology in the United States from the late nineteenth century onward, I was just beginning to realize how staggering the implications of all this really were.
TOM DEMÉRÉ’S BONES AND STONES
THE NAT’S MAIN ATRIUM, WHERE the allosaur lurks, is accessed through the mu
seum’s north entrance, so just before 11 am Santha and I walked around the west side of the four-story building and presented ourselves at the south entrance. Beyond it was a second atrium, where we were encouraged to see that much of the space was devoted to a well-attended exhibition honoring the Cerutti Mastodon Site.
Out of the crowd, Rebecca Handelsman appeared. Tom Deméré would join us in a moment, she said. While we waited, she walked us over to a display case containing a mock-up of the sediment matrix from the site into which, point down and visible through the glass side of the case, was set a mastodon tusk. It was a little shorter than my arm, but it was obviously not complete as the upper part had been crudely broken off.
“This is the tusk that first attracted Richard Cerutti’s attention,” Rebecca explained, and before I could ask she added, “Its upper part was clipped off by the backhoe before he could stop the construction work.”
“Is the way it’s displayed here the way it was found?” I asked.
“Exactly that way.” She paused and waved. “Look, here’s Tom. He can tell you all about it.”
Weaving through the crowd was a man of pleasant aspect, spare and lean after a lifetime of fieldwork, wearing blue jeans and a brick-red shirt. From my background reading I knew he was 69 years old, though he appeared younger, and as we shook hands I saw he had penetrating gray eyes and an easy smile. Despite the risk to his reputation of even talking to a “pseudoscientist” like me, he seemed relaxed and friendly.
I launched straight in on the subject of the tusk. “What’s so special about it?” I asked Tom.
“The way it was set into the ground so it would have stood upright. The other one lay in a natural horizontal position beside it but this one was found like you see it in the display. Vertical. And that, to us, immediately looked like an anomaly.”
“Why?”
“One suggestion is that it was perhaps left there as a marker to come back to the site on a floodplain where everything is low relief. … I mean, who knows? I don’t know what sort of noncultural process would put a tusk vertical. I just don’t understand it.”
“So what you’re saying is that this looks like the result of human behavior? That it’s evidence of a deliberate, intelligent act?”
“It seems like that to me, and to many others—though I have to say our critics aren’t persuaded!”
I take this as my cue to ask Tom if he and his team had been surprised by the level of skeptical response to the Nature paper.
“I expected we’d have pushback,” he replied. “I just hoped it would have been more objective.”
“I suppose that in any profession and any career people get very emotionally involved …”
“Apparently! I’m not used to it from a paleontological standpoint. I mean, there’s passion in paleontology, too, but I’m not used to this sort of thing.”
I restrain myself from stating my view that “this sort of thing”—namely sniping, quibbling, misrepresentation, straw-man arguments, and vituperative ad hominem attacks leveled against anyone suggesting deep antiquity for the First Americans—is perfectly normal among archaeologists, and Santha and I gratefully accept Tom’s offer to talk us through the exhibits.
The anomalous tusk is just a small part of the story, he says. The stronger evidence comes from the mastodon’s fossilized bones, and from the rocks and stones of various sizes found distributed around the site.23
In humans the femur is the long bone of the thigh. At its upper end it has a ball-like protrusion, the femur head, that articulates with a socket in the pelvis and thus—wondrous nature!—enables us to walk. Though they stood on four legs it was no different for mastodons. Their femora were their upper hind limbs and, just like our femora, were surmounted by ball-like heads set into their pelvic sockets.
Tom draws our attention to the hefty, almost hemispherical detached heads of the mastodon’s two femora, one with the rounded end down, the other with the rounded end up, sitting side by side in a display case. “This is how they were found when we excavated them,” he says. And he points out a rock next to them that he calls an “anvil stone,” adding that there wasn’t much left of the femora themselves.
The significance of this is not immediately obvious to me so I ask Tom to elaborate.
“We suggest that this was a work station,24 that both femora were hammered and broken here on the anvil stone and that the heads were detached and just set off to the side. It feels purposeful, like the tusk. It feels like humans were breaking these bones and it’s not only what’s here that’s important but also what’s not here. I mean, originally the femora from which these heads came were three feet in length and massively thick, yet we have just a few pieces of them …”
“So that would suggest, what, that the other pieces were taken away?”
“Yes. I mean, if it was equipment damage, you’d think you’d have the whole femur, right? So the fact that we have missing bits suggests to us that they were taken away, which fits this idea of human processing and transportation.”
In the next display case are the few large fragments of femur that were found at the site and multiple smaller flakes of bone that were found lying around them.
“We interpret these as cone flakes,” Tom explains. “So when a bone is struck by a stone hammer you have damage on the impact side but also you have these flakes come out on the other side. At the point of impact you have a small hole and the exit point of that impact is a larger hole, and so these are flakes that are created by impacts.”
“I suppose one question would be—they took away bits of the femora, so why didn’t they take the tusks? Because the tusks, presumably, would have offered them useful materials, too?”
“But they’re also heavy,” Tom points out. “Whereas bones are relatively transportable. We have a pattern and the pattern begs for an explanation and what we feel fits that pattern is human transportation.”
“Did you find anything that was obviously a tool?”
“No.” Tom appears untroubled by what some critics regard as a fatal argument against his case.
I seek clarification. “So if we’re saying that humans did this, then we’re saying that they just took advantage of natural rocks and they used those as hammers and anvils basically?”25
“That’s one of the problems the skeptics have,” Tom admits cheerfully, “that there are no fashioned tools, no flaked stone tools, that there are no knives, no scrapers, no choppers.”
“But if I’m correct, you’re arguing that can be explained—because what these ancient humans were doing was extracting the marrow from the bones.26 They were smashing up the bones. They didn’t particularly need fine tools for this.”
“That’s what we’re saying. We’re saying that this was a carcass. It wasn’t killed by these humans. It wasn’t even butchered by these humans. Most likely it was a carcass at an advanced stage of decomposition but it still had potential for the extraction of marrow from the bones.”
“Some critics have claimed it was the backhoe or the grader or other equipment used in the roadworks that broke the bones,” I point out.27 “Others have argued that they were broken by being rolled against rocks carried along in river water when the surrounding sediment was laid down.”28
Tom raises an eyebrow. “Flow velocities that are strong enough to transport rocks like the big anvil stones are going to carry all the finer material much farther away. And yet we still have all that fine material at the site—small stones, small bone fragments, and obviously the associated silt and sand, too. So there really is a disjunct in terms of the hydrology.”
Addressing the suggestion of Cerutti skeptic Gary Haynes that the bones were broken by the roadmaking equipment in 1992,29 Tom launches into a long and detailed exposition. It’s too technical to try the reader’s patience with here, but the takeaway is that a recently broken, fossilized bone has a very different appearance to a bone broken when it was still fresh, within a short time of the animal’s death. Ex
periments carried out by Deméré’s colleague Steve Holen on the bones of a recently deceased African elephant showed that the characteristic spiral fractures that occur when you deliberately and systematically break fresh bone between a stone hammer and a stone anvil in no way resemble the fractures caused by the teeth of scavengers or predators and simply cannot occur in fossilized bones.30 The presence of spiral fractures among the bones of the Cerutti mastodon therefore leads to the inevitable conclusion that they must have been broken 130,000 years ago, when they were fresh.31
Meanwhile, the presence of the hammer and anvil stones, and the evidence of how they were used to break the bones, makes it equally certain that humans were involved.32
“Because,” I muse, “nothing else is going to smash up those bones and take out the marrow in that way.”33
“That’s how we see it,” Tom confirms, “but I’m a scientist so I’m open to alternative explanations if they fit the data better than ours. And so it’s possible that we are wrong. But the evidence suggests to us that the only explanation for the taphonomic data at this site is that humans were responsible.”
Taphonomy is the study of the circumstances and processes of fossilization, a field that is generally better understood by paleontologists like Tom than by archaeologists.
IF YOU DON’T LOOK, YOU WON’T FIND
AFTER WE’VE COMPLETED OUR TOUR of the exhibits Tom takes us behind the scenes at the museum into areas off-limits to the public. As we ride the elevator up to the fourth floor I ask him if it was a struggle to get the Nature paper accepted.
“Well, it was a yearlong review process,” he replies, “rigorous, which you’d expect. I’ve tried publishing in Nature before. It’s not an easy journal to get into. So we were excited when they sent it out for review. That’s really the first hurdle—if it gets off the editor’s desk. Then we went through several rounds of revisions and re-review and re-revision but eventually it was accepted. So that was really exciting. It’s a terrific journal. And that’s the other thing, of course, it’s Nature, it’s not some third- or fourth-tier publication.”
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