On a late-summer day in 2001, at the University of Poitiers in west-central France, the palaeontologist Michel Brunet summoned his colleagues into a classroom to examine an unusual skull. Brunet had just returned from Chad, and brought with him an extremely ancient cranium. It had been distorted by the aeons spent beneath what is now the Djurab desert; a crust of black mineral deposits left it looking charred and slightly malevolent. It sat on a table. “What is this thing?” Brunet wondered aloud. He was behaving a bit theatrically, the professor Roberto Macchiarelli recalled not long ago. Brunet was a devoted teacher and scientist, then 61, but his competitive impulses were also known to be immoderate, and he seemed to take a ruthless pleasure in the jealousy of his peers. “Michel is a dominant male,” Macchiarelli told me. “He’s a silverback gorilla.”
Inspecting the skull, one could make out a mosaic of features at once distinctly apelike and distinctly human: a small braincase and prominent brow ridge, but also what seemed to be a rather unprotruding jaw, smallish canines and a foramen magnum – the hole at the base of the skull through which the spinal cord connects to the brain – that suggested the possibility of an upright bearing, a two-legged gait. Macchiarelli told Brunet he did not know what to make of it. “Right answer!” Brunet said.
The discovery was announced to the world the following year on the cover of Nature, the leading scientific journal, and in a televised ceremony in the Chadian capital, N’Djamena. “A new hominid is born,” Brunet declared. “By virtue of his age, he is the ancestor of all Chadians. But also the ancestor of the whole of humankind!”
The skull, which Brunet called “Toumaï” – a name from the Djurab, meaning “hope of life” – belonged to a two-legged animal of the Upper Miocene epoch, between 6 and 7m years old. Assuming it was indeed our distant forebear, it was the most ancient ever found, by a margin of as much as 1m years. The location of its discovery furthermore suggested that the human lineage might not have evolved in the savannas of the Great Rift valley of east Africa, as long understood, but rather about 1,500 miles west, in what were once the gallery forests of the greater Sahara. Toumaï stood to upend our very notions of how and why we came to be, to “fundamentally change the way we reconstruct the tree of life”, one prominent palaeontologist wrote. Brunet, to whom the honour of naming the new species fell, called it Sahelanthropus tchadensis: “Sahel Man of Chad.”
But immediately questions were raised about whether the species was correctly assigned to the human lineage. The authors of a sneering letter in Nature suggested renaming it “Sahelpithecus” (“Sahel Ape”), most notably because it did not, according to their counter-analysis of the skull, walk on two feet – bipedalism being one of the very few available criteria for identifying ancient members of our evolutionary branch. Yet it escaped the notice of no one in the field that some of the letter-writers were affiliated with another hominid species, which had, until the arrival of Sahelanthropus, held the record for the oldest known. And while the question of Sahelanthropus’s gait was acknowledged to be a crucial one, the skull alone was not going to provide a definitive answer. For that, “postcrania” would be required: remains from the neck down, especially the lower body – a pelvis, a femur. Unfortunately, Brunet reported in Nature, none had been recovered.
Brunet became a celebrity scientist. In France, he shared caviar with President Jacques Chirac. In Chad, where he ran a programme of field research, he befriended the dictator Idriss Déby; the Chadian national airline was soon renamed after Toumaï. In 2003, Brunet received a $1m Dan David award for discoveries that “cast a new light on the history of human origins”. In Poitiers, grant money poured in.
Fame made Brunet grandiose and, in the opinion of some colleagues, slightly paranoid. He seemed to assume that everyone everywhere was consumed with the idea of studying Toumaï, “as if it were the most precious thing on Earth”, said Olga Otero, a researcher who worked with him for years. Brunet’s relations with Macchiarelli, in particular, deteriorated. He had recruited Macchiarelli, who was 15 years his junior, from Rome, and he seemed to expect a certain deference. The palaeontology group in Poitiers was organised to an unusual degree around Brunet, its director; he had a tendency to treat the other scientists as if they were his vassals, as mere “service providers”, Otero said, expecting them to conduct research that furthered his own work, and refusing to sign off on projects that did not. Many members, especially the graduate students, put up with it in exchange for the resources and visibility he afforded them, I was told. But Macchiarelli had no interest in pledging loyalty. “Doubts, additional questions, argument and criticism contribute to the strength, not the weakness, of scientific thought,” he told Nature in 2003. Brunet referred to him derisively as “the Italian”, Macchiarelli told me.
In early 2004, Brunet and much of his group were in the Chadian desert with a film crew, making a documentary about Toumaï. In Poitiers, however, a master’s student named Aude Bergeret was undertaking a study of numerous Chadian fossils, including some from the zone where Toumaï itself had been recovered. One of these fossils, listed as an “undetermined long bone”, was scheduled to be cut in half for examination of the sediments inside. Bergeret wanted to be sure to extract as much information as possible from it beforehand. “There came a point where I was making observations, but I frankly wasn’t sure what I was looking at,” she told me. She needed guidance. The adviser who could have provided it was in the desert with Brunet. Macchiarelli, however, who had been one of her instructors, was on hand.
Initially, Macchiarelli declined to examine the bone. He did not want to get between Bergeret and her advisers, he told me, and he was cognisant of the ethical norms of the field, which dictate that one does not study fossils unearthed by someone else without their express authorisation. His relations with Brunet were already tense. And he also knew that Brunet had a special sensitivity about Chadian remains, the most important of which had been recovered under circumstances that were, from Brunet’s perspective, far from ideal.
Brunet had not in fact been in Chad for the discovery of the cranium that made him famous, and had not even authorised, much less directed, the small expedition that found it in 2001. Rather, a geographer named Alain Beauvilain, who handled the logistics of the Chadian operations, had, with three Chadian colleagues, set out from N’Djamena on an impromptu prospecting mission in the desert. Beauvilain, who had already been feuding with Brunet in the years before the discovery, was not shy about sharing these details with the world. As director of the research programme, Brunet was, by convention, the ultimate discoverer, but as soon as the description of Toumaï was published in Nature, he had Beauvilain recalled to France. And since then he had tried, in essence, to write him out of the story.
Examining the Chadian fossils without Brunet’s OK was unorthodox and a bit risky, Macchiarelli realised. But a student was seeking his help, he told me. “In the end,” he said, “I thought to myself, It’s my duty.”
He saw immediately that Bergeret’s long bone was the shaft of a left-hand femur. He took note of its robust diameter, its pronounced posterior ridge, its forward curvature: it was evident to Macchiarelli that it had belonged to a primate. “Aude, where is this piece from?” he asked, attempting to mask his mounting agitation. The femur’s inventory number suggested it had been collected from the same site, on the same day, as the Sahelanthropus skull. The crucial postcrania that Brunet said did not exist evidently did. “Don’t cut anything,” he said to Bergeret. “This appears to be the femur of Toumaï.”
He gave Bergeret some reference papers, told her to spend the weekend making a close study of the femur, and left. “I went back to my office,” Macchiarelli said, “I closed the door, and I said to myself: Shit!”
When he returned from Chad, Brunet was furious. According to Macchiarelli, he immediately spent several days studying the femur in the laboratory, behind closed doors. He soon asked to meet with Bergeret in his office. “Mademoiselle Bergeret, you were entrusted with study materials that were unidentified,” he told her, Bergeret recalled. “It was not your role to make an identification.” A laboratory meeting was convened in the presence of a university dean to discuss a “leak of scientific information”, as the minutes put it. One researcher alleged that there were “people who take advantage of our being away in the field to rifle through our collections”. Brunet spoke of “a Judas”. “A grave professional offence has been committed,” wrote the dean.
In the meantime, Bergeret left for several days of fieldwork. When she returned, she found that her research materials had been confiscated; the fossils were being “renumbered”, she was told. At one point, however, Bergeret said, one of her advisers appeared with the femur in his hand. “This piece,” he warned, holding it before her: “You forget you ever saw it.”
Palaeoanthropology is a notoriously disputatious, not to say vicious, field. In part, this is an effect of self-selection: given its prestige, and its philosophical, even metaphysical implications, the study of human prehistory attracts the most ambitious and, as one member of the discipline put it to me, “the most psychotic”, palaeontologists. There is, additionally, a cultural divide within the field between, speaking very broadly, field workers and laboratory specialists. The former disdain the latter as “armchair palaeontologists”; the latter disdain the former as “fossil hunters”.
But most of the fighting in palaeoanthropology is simply a function of the wild imbalance between the number of palaeoanthropologists, which is large, and the number of objects available for them to study, which is very much not. Our direct knowledge of the first few million years of human evolution derives from a collection of bone fragments that could no more than halfway fill a large shoebox. “It’s a bit frustrating,” the researcher Jean-Jacques Jaeger told me, with some understatement, “but there really is a gap in the palaeontological record between, I’d say, 14m and 5m years ago in Africa.” Among other things, the tectonics of this period were not conducive to fossil formation. Unfortunately, this period is precisely when the human line began.
Still, the greatest conflicts in the field tend not to be over access to fossils but over the sense one makes of them. Attempting to reconstruct the history of early humanity from the available evidence is, it has been said, akin to trying to divine the plot of War and Peace from just 13 of its pages, picked at random. Major disagreements of interpretation are inevitable, as are major errors, and the discovery of a single new “page” can change everything we thought we understood about the broader story. What we call our knowledge of the deep human past is in fact overwhelmingly provisional, contingent upon whatever fossil happens to turn up next.
“Lucy”, the remarkably complete skeleton of a species that came to be known as Australopithecus afarensis, is the most famous case in point. At about 3m years old, Lucy was, at the time of her discovery in Ethiopia, in 1974, by far the most ancient hominid ever unearthed. She looked like nothing anyone had ever seen, with “an unexpected combination of a small-brained, apelike head and a fully erect body”, as the New York Times put it at the time. This strange morphology overturned a century-old presumption about what it was to be human. Until then, the human line was thought to be distinguished from the rest of nature largely by its superior intelligence. Lucy’s brain was tiny. And yet 3m years ago her species was already walking very much as we do. Though perhaps less flattering to our self-conception, uprightness turned out to be our deeper heritage. The smarts, such as they are, came later.
If logic were the only factor, the flimsiness of our understanding would inspire restraint, and new fossil discoveries would only rarely give rise to grand pronouncements about the nature of humanity. But the impulse to make such pronouncements, heightened by the prospect of fame, not to mention grant money, can be overwhelming. There is a large and receptive audience for stories about the origins of humankind, however conjectural the stories may actually be. We yearn to know how and why we came to be ourselves, how humanity emerged out of nature. Frequently we yearn, as any historian of the prehistoric sciences will tell you, to the point of unreason.
The result is a corpus of palaeoanthropological knowledge that is forever being not only revised but effectively rewritten, and then rewritten again. “A so-called science in which every new piece of evidence is claimed to overthrow all previous ideas must either be in a very juvenile state of development,” the palaeontologist Martin Pickford once wrote, “or it can’t really be a science at all, just a string of temporary opinions.” Pickford, a co-discoverer of the 6m-year-old species Orrorin tugenensis, knew whereof he spoke. A few years after he wrote that line, Orrorin was displaced by Brunet’s Sahelanthropus as the oldest hominid, and Pickford was penning his “Sahelpithecus” letter in Nature.
Even bipedality itself, which seemed so crucial after Lucy, is no longer taken as an obvious criterion for human-ness, at least not for the most ancient candidates. Our line evidently began walking upright at some point well before Lucy’s species emerged, but there is no agreement as to exactly when this habitual bipedalism began. It is entirely possible that our oldest ancestors walked not on two feet but four; it is entirely possible, conversely, that the most ancient panins – the ancestors of the chimpanzee and bonobo, our closest living relatives – walked on two legs just like their hominin contemporaries. The only trait that is in fact generally accepted as a reliable marker of our evolutionary branch alone is known as the “non-honing CP3 complex”. It has nothing to do with what most people would say if asked what makes us human. It describes the manner in which, when our jaws are closed, our canines and third lower premolars meet.
Our uncertainty about the nature of humanity is compounded, too, by the realisation in recent decades that the deep past is a far messier place, biologically speaking, than had long been assumed. Most researchers now believe that, for most of the past several million years, numerous hominin species in fact lived simultaneously, much as Homo erectus, the Denisovans, the Neanderthals, and our own species once did. But, setting aside the interbreeding that almost certainly took place – another complication – only one of the hominin species from any given epoch is our actual forebear; the others are our forebear’s cousins, you might say. For purely statistical reasons, we are far more likely to dig up bones from these cousins, who did not give rise to us, than from the rare species that did. In communicating their findings to the lay public, palaeoanthropologists often speak of finding human “ancestors”, but, unless they are referring to the genus Homo, that is only shorthand. “In a pinch, it’s the sort of thing you can tell the media,” one researcher told me. But it isn’t, strictly speaking, true.
Bergeret never saw the femur, or any of her other research materials, again. “In hindsight, I wonder why I didn’t go back and say, ‘What happened to my fossils, actually?’” Bergeret told me. “But I was just a student.” The laboratory seemed to close ranks against her, she said, and after her master’s she was made to understand there was no support for her to take a doctorate. (Several members of the laboratory denied any campaign of exclusion, while acknowledging that individual members probably did behave unfairly toward her.) Macchiarelli intervened, and eventually helped her to become a museum conservator; she currently directs a natural history museum in Burgundy. (She now goes by the name Bergeret-Medina.) To her mind, Macchiarelli rescued her from the worst consequences of stumbling on the femur. “And in a way,” she said, “it damaged his career more than mine.”
In Poitiers, Macchiarelli made overtures of reconciliation to the colleagues who felt him a traitor, he said, including a letter hoping for “a return to serenity”. But it didn’t work. Brunet’s group behaved “like a tribe, like a closed-off family”, he told me, like a “cult”. Brunet ought to have thanked him for bringing an important fossil to his attention, Macchiarelli thought. Instead, he urged administrators not to renew Macchiarelli’s contract. Macchiarelli’s office was relocated; he was forced to clean and supply it on his own, he said, and to buy his own stamps, printer cartridges and toilet paper. Though he remained a professor of the University of Poitiers, he took a research position in Paris. “I was attacked, I was insulted, I was threatened,” he said, of his time in Brunet’s group. “Poitiers is the asshole of the world.”
At the same time, Brunet’s star continued to rise. In 2005, in collaboration with the researcher Christoph Zollikofer, he published a three-dimensional digital reconstruction of the Toumaï cranium, correcting for the various distortions it had suffered beneath the earth. “Now it’s completely confirmed that Toumaï is not a chimp, or a gorilla, but a true hominid,” Brunet said at the time. The same year, the prominent palaeoanthropologist Richard Leakey declared Toumaï “the most important event” in the field in the past quarter-century. In 2007, Brunet was elected to the Collège de France – a tremendous honour for a French scientist – and soon thereafter published a new dating of the cranium, to between 6.8 and 7.2m years. Sahelanthropus tchadensis was, in Brunet’s view, unequivocally the most ancient hominid species ever known, thrillingly close, in all likelihood, to the very moment our line began.
The femur still haunted Macchiarelli, though. At the start, he’d dreamed about it feverishly. “I didn’t sleep for days,” he told me. “I replayed the film in my mind – I’d held it in my hands!” None of Brunet’s papers contained any reference to a recently discovered Sahelanthropus femur, however, and if one read closely, Macchiarelli realised, many of them seemed to implicitly deny its existence. A 2004 journal article reported an “absence of limb bone remains”. The following year, in Nature, Brunet wrote that “several lines of evidence” suggested that Sahelanthropus was bipedal, with the proviso that, in order to be certain, “postcranial evidence will be necessary”; he declined to report that he was now in possession of precisely such evidence. Macchiarelli at one point sent a long letter to the president of the University of Poitiers and several top officials at the CNRS, France’s prestigious research network, in order to “formally accuse” Brunet of lying about what he called “the femur affair”; nothing came of it. “There’s been a selection, a choosing of which remains to publish, and which not,” Macchiarelli told me. “No one has the right to do that!”
Macchiarelli is a compact, voluble man with a winning smile and an endearing minor lisp. He bears a passing resemblance to the actor Dustin Hoffman. He is also a man of considerable self-regard and, by broad consensus, of sometimes unbearable, even aggressive, fastidiousness. Since childhood, his nickname has been “precisini,” Italian for “anal-retentive”, he told me, not without pride. Typically it would be “precisino”, the singular, but just one precisino was deemed insufficient; Macchiarelli was more punctilious than that. “If a comma was missing, I was definitely the one who added it back,” he told me. As a teacher, he added, he sometimes drove students to tears, “even the boys”.
As his concerns about the femur grew, Macchiarelli discovered further oddities. Beauvilain, the banished geographer, had his own fixation on Sahelanthropus, and beginning shortly after the discovery of the femur, in 2004, he had written several articles, in journals of varying degrees of obscurity, attempting to undermine the discovery of the Toumaï cranium itself. In 2009, in a French-language regional geological newsletter, he published photographs of the skull as he alleged it was found, atop the sand, surrounded by various other fossils. Just next to it, no more than about a foot away, was what looked very much like a femur. It had been there, it seemed, from the very start.
Macchiarelli had initially assumed that Brunet was keeping silent about the femur for essentially emotional reasons, out of shame for not having been there for its discovery in the desert in 2001, and for not having recognised it afterward. By now, however, he had come to suspect that Brunet was in fact hiding it “because it didn’t fit”, he said – because it seemed to show that Sahelanthropus was not a biped, and presumably not a hominin at all, and because Brunet’s reputation would be shattered if anyone found out.
Beauvilain’s photograph constituted the first public confirmation of the femur’s existence. It gave Macchiarelli an opening. In 2004, Bergeret had taken several laboratory photographs of the bone. Macchiarelli now brokered the publication of two of them on the widely read blog of John Hawks, a University of Wisconsin-Madison professor and longtime Sahelanthropus sceptic. In principle, to print images of someone else’s unpublished fossil was a clear breach of ethics. But then, Macchiarelli, Bergeret and Hawks reasoned, after Beauvilain’s article, the femur was no longer unpublished.
The photographs went up on Hawks’s blog in the summer of 2009. They showed a small blackened shaft run through with fissures, ragged at the top and bottom, where the important end pieces had long since broken off. It resembled a length of burnt kindling. From the images alone it was impossible to say whether the bone had belonged to a biped, Hawks assessed. He called upon Brunet to make a formal description: measurements, scans, comparisons to other primates. It was “perfectly legitimate” for a scientist to delay addressing certain subjects “until you’re ready for the sun to shine on them”, Hawks wrote, but “some ideas need more sunshine than others”.
Brunet likes to say, with only slight exaggeration, that it took him 30 years of digging before he found anything of consequence. Fieldwork is gruelling and slow, and always a gamble. In the 1970s he went to Afghanistan, prompted by the nearby discovery of Ramapithecus, a 14m-year-old creature then thought to be a direct human ancestor. He was effectively deported after the Soviet invasion, in 1979; Ramapithecus turned out to be an ancient orangutan. He went to Cameroon. No hominins had ever been found there. “It wouldn’t have been very innovative to try to follow the people who were already in east Africa,” he told me recently. A close friend came to help; he was killed by a drug-resistant strain of malaria. Brunet found nothing. Only then did he try Chad.
The Djurab is a particularly difficult research environment. The zones of palaeontological interest typically require several full days of Jeep travel to reach; daytime temperatures can rise to about 50C. The winds whip stinging sand, and can sometimes cause a dune to migrate as much as 5 metres in a single night. Beneath the dunes lie compact sediments; when they are exposed, the winds erode them at a rate of a few centimetres per year. The fossils are left behind. Often they have been fully excavated by the wind, and come to rest gently upon the surface of the desert, strewn about and forgotten like the playthings of some primeval child. Eventually, inevitably, the winds cover them again with sand, if they do not destroy them first. In the Djurab, one must not only come to the right place, but arrive there at the right time.
I visited Brunet last year in Poitiers, where he picked me up from the train. He’d suggested we meet at a parking garage attached to the station, the “Toumaï lot”; on the way there I passed the municipal conference centre, the “Espace Toumaï”. Brunet was waiting behind the wheel of an ageing Mercedes, looking over the reading glasses perched at the tip of his nose. He greeted me slowly, as if sceptical of my intentions, and then began to deplore the unsettled state of French society, and of science. “Sometimes I feel as if I come from another world,” he said. He is now 85. A white beard tapered to an elfin point beneath his chin, and bright cerulean eyes twinkled beneath the wisps of his eyebrows. When he emerged from the car, he took out a cane and began hobbling away. He’d lost 7cm of height to the Djurab, he said; several years ago, after a heart attack, he’d had a defibrillator implanted, such devices being rare in the desert. He asked that I follow him. “It won’t be hard!” he laughed. No one has ever questioned his commitment.
Brunet was furious at the publication of the photographs of the femur. “When these little young people who have only ever worked with CT scanners or at the synchrotron come tell you how the world works, but they’ve never once found an actual fossil of their own – well!” he told me. Whatever the methodological conflicts within palaeoanthropology, it is a matter of near-universal agreement that, for having put in the time and effort, and for having made the initial gamble to dig wherever they dug, the discoverer has the sacred and inviolable right to be first to study their fossils, and first to publish them. In practice, Brunet noted, this often means a wait of many years.
Brunet told me he’d never sought to keep the femur “hidden”, exactly, and that he’d in fact known of it from the very start, since its discovery in the desert in 2001. He did falsely deny its existence, including in print, but, contrary to Macchiarelli’s assumption, this had nothing to do with what it showed about Sahelanthropus, he said. In Brunet’s opinion the femur obviously belonged to a bipedal hominin, but bipedalism in Sahelanthropus was already clear from the skull. “It only confirmed what you could prove without it,” he told me. He had attempted to keep the femur out of the public eye because it was quite a damaged, difficult specimen; he assumed, wrongly as it happened, that he would soon find other femora, and that these would make for a more conclusive publication. “I was too optimistic,” he said.
As proof of this version of events, Brunet offered that in 2001 or 2002, well before the bone turned up in Poitiers, he’d in fact taken the fossil or a cast to the United States, where he showed it to four prominent palaeoanthropologists: C Owen Lovejoy of Kent State, David Pilbeam of Harvard, Tim White of Berkeley, and Bernard Wood of George Washington. “Ask them!” Brunet said. When I did, three of the men said they had no recollection of seeing a femur at the time in question, though two did recall seeing one a few years later; one man, noting that he was a “close friend” of Brunet, declined to comment. When, in a later conversation, I brought these details to Brunet’s attention, he said he’d made a mistake about the timing but maintained that he had absolutely known about the femur from the outset. If that is true, he seems not to have made anyone else aware of it. Nor does he seem to have made any particular effort to keep it safe. On the contrary, for Bergeret’s study, he’d authorised that it be cut in half.
His former colleagues tend to believe that Brunet did in fact see the fossil in 2001, when he came to N’Djamena to collect the cranium, but that he failed to realise what it was. Beauvilain told me he’d pointed it out to Brunet specifically – “Wait, what about that thing? Isn’t that something curious?” – but that Brunet seemed uninterested. Jean-Renaud Boisserie, a CNRS senior researcher who worked with Brunet for many years, recalled that Brunet was “consumed by the skull” when it was found, “completely staggered”. “I don’t think he was in a state of mind to examine any other fossils,” Boisserie said.
Brunet was almost certainly also preoccupied with shaping the story of how the skull had been found, his colleagues said. Franck Guy, a palaeoanthropologist at the CNRS and the University of Poitiers and, like Boisserie, a former disciple of Brunet, said Brunet would have had a “dual reaction” to the discovery of the cranium on an unauthorised, wildcat expedition. “The first reaction is, ‘This Beauvilain asshole has once again taken a shit in my boots! And now I’m going to have make sure the shit doesn’t get out of them.’” (Initially, Brunet agreed to speak with me only if I agreed never to speak with Beauvilain; the articulation of this demand was complicated by his refusal to speak Beauvilain’s name aloud.) The second reaction, according to Guy – no less consuming or obsessional than the first – would have been: “Holy shit, we’ve clearly got the oldest hominid. We licked all those other fucking bastards!”
After Hawks’s 2009 blogpost, Brunet felt enormous pressure to make a formal description of the femur, and resented it. Toward the end of that year, during a presentation in London at the Royal Society, at a conference attended by many of the field’s biggest names, he addressed the audience angrily at one point. “My feeling is that you are thinking about postcrania!” Brunet said, his voice rising nearly to a shout. (In a recording of the talk, one can hear what sounds like a hand pounding on the dais.) Before his assembled peers, he declined to confirm or deny the existence of a femur. But he promised: “A description of postcrania is coming.”
No description came. Brunet seemed to take the demands for publication as an attempt at a putsch, his colleagues told me, an intolerable effort to wrest away control of a fossil that, to his mind, would still be buried in the Djurab but for the research programme he founded. And though he was spending ever more time in Paris, at the Collège de France, Brunet still made chaos in Poitiers. Guy told me that two major studies on Sahelanthropus – one on the geochemistry of the cranium, the other on the Sahelanthropus brain – were conducted at the time. The results of both were broadly in line with Brunet’s pre-existing ideas, but neither were ever published. In both cases, Brunet had gotten into disputes with his coauthors, including disputes about authorship credit, and no solution could be found. “Everything was always suffused with this extreme feeling of, ‘I’m the boss around here,’” Guy said.
At the start, Guy and his colleagues had essentially aligned themselves with Brunet in the femur conflict. In their view, Macchiarelli had behaved with wild disregard to ethics at least twice: first in 2004, when he examined the Chadian fossils without authorisation, and then in 2009, when he helped arrange for the publication of the photos of the femur. But Brunet himself was becoming increasingly unbearable, they felt: the behaviour they might have accepted as subordinate graduate students was no longer tolerable as professional peers. And his continued refusal to publish a description of the femur was damaging the reputation of the research group in Poitiers. Guy and Boisserie, who rose to positions of leadership there in Brunet’s absence, began to insist that he publish the femur. He was unmoved.
At the same time, Macchiarelli’s preoccupation with the unpublished femur seemed only to intensify. “For years, I thought about it every day,” he told me. He wrote repeatedly to university administrators to remind them of what he called the “damnatio memoriae” – the erasure from official history – to which the fossil had been condemned, to alert them to the “growing scepticism” of non-French researchers, and to warn that he might have no recourse but to go to the media. And he began to press Brunet’s former disciples, though they were, in his view, still in thrall to their mentor. “It was still him pulling the strings,” Macchiarelli told me. “I didn’t for one second believe in their good faith.” (Guy described this pressure – which took the form of long, rather pontifical emails with the university leadership copied in, or disparaging comments to outside colleagues at academic conferences – as “harassment.”)
Eventually, Macchiarelli had had enough of waiting. “From 2004 to 2018, as one says in proper French, Je fermais ma gueule” – “I shut my trap” – Macchiarelli told me. “In 2018, I decided it wasn’t worth it any more.” The research group in Poitiers was hosting a major palaeontological conference that year. With Bergeret, Macchiarelli submitted an abstract for a presentation in which, using Bergeret’s photographs and measurements from 2004, they would finally describe the femur. It was, he acknowledged, a violation of the norms of his field. “Perhaps another researcher would not have done it,” Macchiarelli told me, lauding what he considered to be his “act of courage.” His was the role of the “white knight”, he said.
The proposal was refused by the conference’s scientific committee. “Never in my life have I had another abstract rejected,” Macchiarelli told me. In a letter to the presidents of the University of Poitiers and the CNRS, among other recipients, he warned that the rejection threatened “the international credibility of French palaeoanthropological research.” He also spoke to the press.
Two days before the conference opened, Nature published a news story that began, “When anthropologists meet in France at the end of January, one of the most provocative fossils in the study of human evolution will not feature on the agenda.” One conference participant told Le Figaro: “There hasn’t been a formal session on Toumaï. But it’s the only thing being talked about at all the coffee breaks!” The conference’s scientific committee insisted that Macchiarelli’s abstract had been rejected for ordinary reasons – other abstracts had been rejected, too – but there were, Le Monde reported, “suspicions of omertà”.
For the researchers in Poitiers, the coverage was a catastrophe. “We were going to show that we’ve changed leadership, that we’re making a new start,” Guy told me. They were just beginning to emerge from what they considered to be the sinkhole around Brunet; Macchiarelli pulled them back in.
For outsiders, the bitterness and intractability of the femur dispute was sometimes mystifying. The University of Poitiers attempted a mediated solution, and at one early meeting the university’s vice-president for research remarked that Macchiarelli “seems a bit frustrated not to be able to study this specimen”, Guy recalled; “Just give it to him,” the administrator suggested. Guy, a generous but brooding man with a shaved head and an air of unmistakable weariness – weariness with Macchiarelli, with Brunet, with being stuck between them, with how puerile science sometimes is – noted ruefully that the vice-president was a physicist by training. “We had to explain to all these people how things work within our discipline,” he told me. Eventually, however, an agreement was reached. The researchers in Poitiers would, with Brunet’s approval, finally publish a formal study of the femur. In the meantime, and until publication, Macchiarelli would stop talking about it in public.
Macchiarelli broke the agreement. In November 2020, in the Journal of Human Evolution, or JHE, one of the top publications in the field, he, Bergeret, and two co-authors published their own formal description of the femur, the first ever made. Based largely upon the bone’s apparent forward curvature – in Homo sapiens, the femur is effectively straight – and what little they could glean of its internal structure from Bergeret’s photos, the authors concluded that it had probably belonged to a quadrupedal, non-hominin ape.
Without access to the fossil itself, the paper was “mediocre”, Macchiarelli acknowledged. But it was beyond time for a formal description: without one, he felt, the entire field was being misled, our vision of humanity itself distorted. The year before, a respected colleague in the US had published a paper in which he referred to Sahelanthropus tchadensis in definitive terms as a “hominin” and the “earliest species known.” “If he’d seen the femur, he wouldn’t have written the things he wrote!” Macchiarelli said. And he assumed that, despite the agreement, Guy and his colleagues had no plans to publish. “I waited, I waited, I waited,” he told me.
Even given Macchiarelli’s history, the researchers in Poitiers were astonished at what he had done. He had now, irrevocably, made the first formal description of a specimen that he had not himself discovered and to which he had never actually been granted access, including by the ultimate rights-holders, the authorities of Chad. Nor had Macchiarelli in fact been quite so unaware of any plans to publish. Two months before the appearance of the JHE article, the scientists in Poitiers had posted a preprint manuscript of their own study online; Macchiarelli had seen it, he acknowledged to me. He went ahead with his own article anyway.
The researchers in Poitiers wrote to the JHE to warn that Macchiarelli’s paper was “presumably subject to scientific integrity issues”. They also filed a formal ethics complaint with the CNRS. Neither undertaking had much effect. “We understand how upsetting this is for you,” the editors of the JHE responded. After more than 70 hours of interviews, a CNRS investigatory committee determined that it would make no pronouncement on Macchiarelli’s behaviour. In their brief report, they offered no specific logic for sitting on their hands but did make note, with apparent apprehension, of “the potentially media-attracting character of this affair”.
The researchers pressed on with the femur. Their finalised study was published in Nature in 2022, 20 years after the Toumaï cranium first appeared in the pages of the same journal. Brunet was not among the authors, and told me he had declined to participate out of lassitude with the “polemic” around the femur. According to Guy and Boisserie, he had in fact demanded to be credited as lead author, and had withdrawn his name when they refused. It was the end of cordial relations. Guy put the conflict in Oedipal terms. It had taken them many years, he said, but he and his colleagues were finally able to “kill the father”. Brunet now calls them “the young ones” – Guy and Boisserie are in their 50s – or the “little idiots”.
For the Nature study, Guy and his co-authors had measured the femur and two Sahelanthropus ulnae – bones of the forearm – across a total of 23 distinct parameters, working from high-resolution scans. The “most parsimonious hypothesis”, they concluded, was that Sahelanthropus was indeed a habitual biped, albeit one that probably engaged in a good deal of “arboreal clambering”. It would have been a flat-faced, small-brained creature about the size of a human child or small chimpanzee, perhaps scampering into the trees when a saber-toothed cat came round, perhaps hanging on branches, perhaps sleeping in nests as modern apes do, and presumably moving about much of the rest of the time on the ground, where it walked on two feet. Brunet felt vindicated. Whatever his relations with the authors, “they did an excellent paper”, he said.
More consequentially, if Sahelanthropus was bipedal, then bipedality was in all likelihood a marker of the human lineage from the start. In combination with our distinctive “non-honing” dentition, it was a possible “synapomorphic signature of the hominin clade”, the authors wrote: a functional definition of what it is and always has been to be human. “I don’t want to say we’re categorical about that idea,” said the researcher Guillaume Daver, who shared lead authorship with Guy, but “we have no evidence to contradict it”. Humankind: small dull teeth, two legs.
Macchiarelli called the paper out of Poitiers a “fairytale”. When I asked about its methodology, he chided me, “Please be serious.” (When I asked how such a ridiculous paper had been selected for publication in a top scientific journal, he alleged that, when it came to Sahelanthropus, Nature could not be trusted. The magazine had published the Toumaï cranium 20 years before and other Sahelanthropus papers since; it was now committed, he claimed, to showing that the species was bipedal.) Last year, in the JHE, Macchiarelli published a response, reaching conclusions that were precisely the inverse. When I spoke with his co-author Clément Zanolli, he offered a wry compromise with the findings of the Nature paper. “It’s not impossible that Sahelanthropus could have used bipedalism,” Zanolli, a CNRS researcher and former student of Machiarelli, told me. “Just like chimpanzees do occasionally today.”
In the view of other palaeoanthropologists, the interpretive approaches of both papers were in fact entirely reasonable. Yet by the laws of formal logic, at least one of them was wrong. We have grown accustomed to seeing this sort of scientific impasse resolved through improvements in technology: a new tool makes it possible to extract the pivotal data that had once been inaccessible. But it is hard to imagine pulling much more morphological information from the Sahelanthropus femur. For their study, the researchers in Poitiers scanned it via micro-CT a total of 5,984 times, resulting in 4,962 “slices”. Every feature of the bone as small as the width of a human hair was recorded in three dimensions.
Such exquisite accuracy is of obvious value, but it is also deceptive in a way; in the palaeoanthropological context, it is perhaps even slightly absurd. The defining problem in palaeoanthropology is not one of precision; the problem is that, because we know so extraordinarily little of our deepest past, we can only guess at the meaning of the measurements we already have, however precise they may be. The Sahelanthropus femur is the only possibly hominin lower limb bone ever recovered from before 6m years ago. Without anything contemporaneous to compare it with, even the premise that the fossil being studied in such incredible detail belongs to Sahelanthropus, and not to some other animal, is itself no more than a hypothesis. The maddening irony is that the same scarcity of evidence that makes the femur so important and so tantalising also makes it all but impossible to interpret with any meaningful degree of certainty. “The basic need in this field,” the palaeoanthropologist Tim White told me, expressing a position of rare consensus in the discipline, “is the recovery of new fossils.”
Slowly, as more remains come to light, certain questions will be answered. Others will not be, and cannot be. The question of the true nature of Sahelanthropus, and of its relation to us, may be of that latter, insoluble category. “Just because you want to know something, it doesn’t mean you can know it,” said the palaeoanthropologist Bernard Wood. If Sahelanthropus is indeed a hominin, statistics all but rule out the possibility that it is an actual human ancestor. The most that can be said is that it “represents humanity as it might have been 7m years ago,” Guy said: that it came into being according to the same evolutionary pressures that made our ancestor, whoever it was.
We will almost certainly never find fossils from that ancestor, and in truth we wouldn’t know it if we did. We could one day hold in our hands the remains of the literal ur-mother, the individual animal that birthed the whole of human history. There is no technology, extant or imaginable, that could extract that marvellous secret from her bones.
Fossils promise untold knowledge; fossils promise worldly fame. Often they withhold both; sometimes they drive people mad. They do stir up “an irrational element”, Macchiarelli acknowledged. But as a responsible scientist, adding careful bricks to the great edifice of learned wisdom, he said he had never been swayed by such human passions. “I’m not on a crusade!” he told me, in regards to Sahelanthropus. “I simply think the femur is not at all compatible with bipedality.” Brunet prefers to ascribe Macchiarelli’s two-decade preoccupation with the femur to jealousy. “And jealousy,” Brunet is fond of saying, “is a disease with no cure.” (“Impossible!” Macchiarelli retorted: “for inexplicable reasons”, jealousy “is not part” of his psychological repertoire.) The Toumaï fossils seem to cause a certain derangement, Brunet went on: “Everyone who’s come near Toumaï, who’s touched it – it’s gone to their head.” Like his antagonist, he seemed to imagine himself exempt.
Lately Brunet has turned his eye to chimps. For reasons no one entirely understands, the remains of ancient panins are much rarer even than the fossils of ancient hominins. “Three teeth, a femur – maybe,” Daver told me. They would be of tremendous use in identifying and understanding the species of our own line, a sort of Rosetta Stone. If we cannot know ourselves by what we were, we can know ourselves by what we were not. Brunet has been digging for them in Cameroon. He would like to return to the Djurab.
His former disciples now control the research programme there, however, and they have prevented him: he has a habit of creating problems for them in Chad, as elsewhere. He also seems to have a plan to die in the desert, I was told repeatedly. His former students do not wish to take on the moral burden of allowing him to carry out this plan, or the logistical burden of the aftermath. Repatriating a cadaver is never straightforward, one researcher pointed out drily, but the desert can be especially capricious with human remains.
Reporting for this project was supported by a Silvers Grant for Work in Progress from the Robert B Silvers Foundation
