We will not dwell on the Pit of Bones.
People who have been there have a lot to say about it: a place where 250,000 years ago, human beings dragged several dozen corpses of other human beings into a cave and--who knows why?--dumped them down a 46- foot shaft. With a dull thwack the corpses must have landed, the base of the shaft being a muddy slope; arms and legs flailing like rag dolls, they rolled and settled into a low chamber that is the true bottom of the pit--a chamber without exit. Later, bears looking to hibernate blundered into the shaft, and some of them survived the fall long enough to gnaw on the human remains. Foxes also took the tumble, as did a lion or two. Over many centuries, a rich layer of animal remains built up on top of the jumbled human ones--and then the original mouth of the cave closed somehow, leaving all the bones undisturbed for many millennia. The wet clay preserved them perfectly. Not until the Middle Ages, judging from graffiti in the cave, was the pit rediscovered by the lads from Ibeas de Juarros, a village just down the hill and across the wheat fields.
Ibeas and the hill--a line of low crests called the Sierra de Atapuerca--are in north central Spain, a few miles east of Burgos. They are not far from Pamplona, where young men to this day choose to be chased through the streets by angry bulls. In Ibeas the streets are more apt to be filled with sheep, and at some point the boys there took to proving their manhood by venturing into the Pit of Bones--the Sima de los Huesos. The idea was to fetch bear teeth for the girls. Getting the teeth was not easy, after all. Just to reach that 46-foot shaft, with the original entrance closed, you had to spelunk through more than 1,600 feet of cave, a few hundred of them on your hands and knees, a few tens on your belly. Eudald Carbonell i Roura, José María Bermúdez de Castro Risueño, and Juan Luis Arsuaga Ferreras started making that journey in the early 1980s--but in their case it was not for love, or at least not for the ordinary kind. Carbonell is an archeologist from Tarragona; Bermúdez and Arsuaga are paleoanthropologists from Madrid. In 1976 a graduate student had descended into the Sima and had emerged with bear teeth, yes, but also with a very old human mandible. That jawbone is what started it all.
Nowadays, though, only Arsuaga mines the Sima, along with his team from Complutense University. Carbonell and Bermúdez prefer to work outdoors. Carbonell has vivid memories of his seasons in the pit. One of the first things he and his colleagues had to do was carry out, on their backs, four tons of mud churned up by centuries of bear-tooth hunters. It was awful, he says. It was very, very, very hard. I remember: it was very, very, very hard. One day in the Sima he found himself nodding off-- not from the fatigue of digging for hours in a space in which he couldn’t stand up, and not from boredom, but from the lack of oxygen. He tried his lighter; it wouldn’t ignite. His companions were dozing too. He shook them awake and they all crawled out to daylight, gasping. Many times, Carbonell goes on, visitors who could not stand the close confines had to be hauled out of the Sima, through a passage that narrows to less than two feet. One time a television producer had a heart attack in the cave.
But we are not going to dwell on the Pit of Bones.
For although it offers an incomparable view of a deep past--the bones in it belong to the ancestors of Neanderthals--lately the pit has been upstaged by a second site a few hundred yards away. In a sediment- filled cave called Gran Dolina, a cave you dig rather than crawl into, Carbonell and his colleagues have found bones that are three times older than those in the Sima--at 800,000 years old they are the oldest human remains in Europe. Their anatomy has turned out to be peculiar. The teeth, especially the premolars, resemble much older teeth from Africa. The lower jaw is like that of the Sima people and their Neanderthal descendants. But the face--the face that has emerged from the clay at Gran Dolina is the most surprising thing of all. It is so surprising, we must rethink human evolution to fit that face, says Arsuaga. The Gran Dolina face is 800,000 years old and yet distinctively ours. It is almost that of a modern human.
The Spanish researchers believe it belonged to a previously unknown species of human, one that is close to our last common ancestor with the Neanderthals. They call the species Homo antecessor--meaning Man the Pioneer, or perhaps Man the Scout. Around a million years ago, they say, antecessor walked out of Africa, through the Near East, and across southern Europe to Spain. There it found its way to Atapuerca, which must have been a nice place to stay.
Hills like green elephants loom out of the mist, ahead and to the left of Eudald Carbonell’s aging Land Rover as it rumbles east along the national road from Burgos. A townhouse development looms briefly on the right. It is 8:45 on a Monday morning in mid-July, and Carbonell is a few minutes ahead of the vans that are carrying his team, the 60-odd young scientists and students who dig at Gran Dolina. As he leaves the paved highway at Ibeas, he pulls into the parking lot of an inn called Los Claveles. Stepping up to the bar, he snorts down a chico chica--a mix of two liquors, one of them clear and hard. This is how the farmers get started in the morning, he explains. Here at the foot of the Sierra de Atapuerca, in the gentle valley of the Arlanzón, men have been farming for 6,000 years. Carbonell has been coming here for the past 20, from Rovira i Virgili University in Tarragona. The barmaid puts the drink on his tab.
The Land Rover bounces north now along a dirt road, through windblown waves of golden wheat that emit an almost subliminal sparkle of red poppies. The hills lie straight ahead. They are much older even than the farms, of course--the bedrock is Cretaceous limestone, laid down in a shallow sea that once separated Spain from Europe. Later the limestone was pushed up in the great tectonic squeeze that made the Pyrenees; much later, groundwater ate tunnels through it; and later still the Arlanzón cut its valley, thus drawing the groundwater down out of the hills. The tunnels became hollow caves. During the Pleistocene Epoch, which began around 1.6 million years ago, they slowly filled with sediment that blew or washed in through their entrances. For much of that same epoch they were available as shelters to humans and other animals. The stacked layers of sediment, each one a former cave floor, are now laced with remains.
Caves and Carbonell go way back. He was raised in the eastern Pyrenees, in Catalonia, and it was there he found his first fossil at age five. He organized his first archeological dig at age twelve, in the mouth of a cave--he found some Bronze Age ceramics and some Roman coins that are still displayed in a museum. The cave was near a quasi-fascist Catholic boarding school that Carbonell was attending with little success and much evidence of the wildness that led his mother to consign him there in the first place. Caves were a refuge for Carbonell--although one time he and some boys under his influence nearly drowned in one when a sudden thunderstorm filled a tight passage they were crawling through. Tales of youth, he says now, chuckling, but sometimes life makes sense in retrospect; some people seem born to their parts in it. At Gran Dolina the workers wear colored hard hats to protect them from falling stones; but Carbonell--tall, mustached, ruggedly handsome and hale at 44, a man who stands out, even in a physical and extroverted culture like Spain’s, as someone who never lets a back go unslapped or a shoulder unsqueezed, a man who sings aloud in crowds--Carbonell does not wear a plastic hard hat. Scrambling up the scaffolding to the dig, he wears his pith helmet.
The dig where Homo antecessor made his first and so far only appearance is notched a few stories up into the wall of a canyon that is really an abandoned railway trench, the Trinchera del Ferrocaril. Early in the century a British mining company cut the trench through the southwestern slope of the Sierra de Atapuerca; the railway moved iron ore from a mine in the Sierra de la Demanda, 30 miles to the southeast, to a junction near Burgos. Period photographs show what a blot on the landscape the Trinchera was when it was new. But in places now--the places where you can’t see Carbonell’s scaffolding--it looks almost organic, even beautiful: the canyon walls have weathered, bushes and wildflowers have reclaimed the floor, and holm oak pours over the lip. The glimpse you get of the trench as you come up from Ibeas, and look down it to where it bends out of sight, is an image that sticks with you. It looks like an icon of the Path Through Time: Click here to enter the past.
Naturally it has not been that easy; for Eudald Carbonell, things have only recently started to click. But standing with him now on the scaffolding, facing the seven-by-ten-foot cut in the layered sediments, you can picture the place as it once must have been. The scaffolding collapses noiselessly, the Trinchera fills beneath you, the limestone walls and roof of the cave reassemble themselves and the sediment in front of you melts away, until finally you are standing in the cave of Gran Dolina, circa 800,000 years ago. The morning sun that had burnt through the mist and brightened the Trinchera is gone now, and the only light is that which filters down from the small cave mouth, 40 feet behind you up a gentle, rubble-strewn slope. A few feet in front of you, a small party of humans is energetically stripping the meat off bones, wielding rough stone tools. They are snapping and smashing the bones to get at the marrow. Is it fear of predators that has caused them to retreat so far into the dark? Is it shame? Their feelings are lost to us, they will not fossilize, only the bones they are butchering will, and those bones belong to the butchers’ own kind--an eleven-year-old boy or girl; a couple of toddlers of three or four. But more on that later.
From the floor of the Trinchera you see the cave in cross section: the walls and undulating roof of white limestone framing a giant bulb of red mud that fills the cave to the top. In some places animal bones stick out of the mud. Other people had noticed them even before Carbonell came to the site in 1978, working under the supervision of a paleoanthropologist named Emiliano Aguirre. The human mandible from the Sima was what had attracted Aguirre and Carbonell to Atapuerca, but they started digging at Gran Dolina first. At the time it seemed more straightforward.
A few years into the project, in 1982, Bermúdez came to visit. He and Carbonell had drinks at Los Claveles and became friends for life. Bermúdez was a young paleoanthropologist, he had always wanted to study human origins, but he had a problem: there were next to no human fossils in Spain. His Ph.D. adviser had directed him to study the origin of Canary Islanders instead--the question of who had settled the islands a thousand years ago--which Bermúdez had done, by analyzing teeth in a museum collection. His expertise in teeth would later come in handy, but pulling teeth out of museum drawers was not how Bermúdez had pictured his career. His first field season at Gran Dolina was more like it. It was very strong archeology, he recalls, a smile spreading over his affable, slightly pudgy face. The English word jackhammer eludes him, and so he mimes it. My impression was, ‘Wow, this is fantastic!’
Carbonell, however, had already been digging for five years, and whatever appeal the power tools had was wearing thin. Those were very difficult times for the excavation, he says. Harsh times. We didn’t have much in the way of resources--it was a very small team. For years we just picked things out of the railway cut. There was the problem of how to attack the site--it was enormous, and we didn’t know where to start. The only reasonable place, really, was at the top; the only way to date bones and artifacts properly and to re-create their original context is to excavate a site layer by layer. Which is why Carbonell and Bermúdez were standing on top of Gran Dolina in the summer of 1983, jackhammering through the limestone roof into the first layer of sediment, 150,000 years old or so, jackhammering and pick-axing and sweating like bulls in the dust and the Castilian sun--and not finding much. Even then Carbonell suspected, from what he could see in the wall of the trench--he had even found a few flint tools--that much older sediments in the middle of the stack were going to be the rich ones. But getting there from the top was a job that would require more money and a bigger team.
In the Sima de los Huesos, on the other hand, you couldn’t fit a bigger team even if you had one--five or six live bodies is about all the pit will hold. And though the work there was painfully hard, it was nearly certain to be repaid with human fossils. So Carbonell and Bermúdez slowed the excavation of Gran Dolina for a while and spent the mid-eighties attacking the Sima with Arsuaga. In 1989, Arsuaga finally passed the bear bones and reached a level where he was finding human bones almost exclusively. Then in 1992 he and his colleagues pulled from the Sima the most complete Homo skull ever found that was not modern Homo sapiens--more complete than any of the many Neanderthal skulls, it was, and 200,000 years older than most of them. The Sima skull soon appeared on the cover of Nature, the prestigious British journal. Things had at last started to go well at Atapuerca. Carbonell had been digging there for 15 years, Bermúdez and Arsuaga for 10.
Now they began to get the resources--the state government of Castilla y León increased its support--to attack Gran Dolina properly. Carbonell set a team to work on a small test dig, that seven-by-ten-foot notch in the Trinchera wall, with the plan of starting at the top of the cave and working right through to the million-year-old sediments at the bottom. By the end of the 1993 field season, the team was nearly down to the level they thought was 500,000 years old. They were moving slowly but steadily. Then they got a little prod from the competition.
In early June 1994, a month before the next round of digging was to begin, Carbonell picked his copy of Nature out of the mailbox, and this time on the cover he saw, in large type, the words the first european? underneath a picture of a human tibia. The shinbone had been found at Boxgrove in southern England, and dated at around 500,000 years ago. That made it the same age as a famous jawbone, the Mauer mandible, that had been unearthed near Heidelberg, Germany, in 1907. Though a jawbone is hard to connect to a shinbone, the Boxgrove researchers assigned the two finds to the same species--Homo heidelbergensis--more or less by default. For nearly a century no other human bones of that age had been found in Europe, and certainly no older ones. A commentary accompanying the article strongly suggested that no older bones would ever be found. In spite of clear evidence that an early species of human, Homo erectus, had wandered out of Africa a million years ago at the latest, Europe seemed to have remained an uncolonized backwater until 500,000 years ago. How do we explain this? the Nature commentator wondered.
That got Carbonell’s blood up. He knew in his own personal bones that he had older Europeans at Gran Dolina--he had picked some of their stone tools out of the Trinchera. He called Bermúdez and Arsuaga on the phone. The three of them, joint directors since 1991 of all the excavations at Atapuerca, agreed to send a special team right away to move faster on the dig. Otherwise they might have spent an entire frustrating field season not getting to the depth of history the Boxgrove workers had already reached. When Carbonell got to Gran Dolina at the usual time on July 1, the advance men had raced through more than six feet of sediment. The next week was burned in his memory.
On July 2 the diggers found teeth--the teeth of the water vole Mimomys savini. This was exciting news. Mimomys is known from sites all over Europe, and it went extinct around 500,000 years ago. Its molars had roots, which distinguishes them from the rootless molars of the vole that succeeded it, Arvicola terrestris. The Boxgrove tibia had been dated by the vole clock: it came from right after the transition from Mimomys to Arvicola. No human artifacts or remains had ever been found in association with Mimomys, anywhere in Europe. Until now? Now we knew the rodent was there, Carbonell says. We still had to find tools and hominids.
The tools came during the week. Then on July 8 an excavator named Aurora Martín Nájera extracted three more teeth from the dirt, teeth that were not from a vole. Martín, fittingly enough, was the veteran of the team, with 14 seasons of poking around Gran Dolina--almost as many as Carbonell himself. Maybe you have to have had that experience of long and mostly fruitless effort to understand the pure joy that a few teeth can arouse. Anyway Martín restrained herself. She knew what they were, but Bermúdez, the tooth expert, was summoned to confirm. He confirmed. They were human teeth, all right, and more--they were very old human teeth.
One of them was a premolar, the type of tooth that is situated between the molars at the back and the canines at the front corners of the mouth. Standing on the scaffolding next to the excavation, turning this premolar over in his hand, Bermúdez could see right away that it had a complex root, with three canals for the pulp--the nerves and blood that keep a tooth alive. Pulp canals in one tooth might seem a small feature to focus on at a time like this, and a ridiculously small one on which to build a grand statement about human evolution. But there it is: every premolar ever found before in Europe, from those associated with the Mauer mandible to those attached to modern humans, had a single root, not three. The Gran Dolina premolar looked old and positively African: Homo erectus, Bermúdez thought.
The presence of Mimomys teeth in the same layer of sediment showed that the human teeth were older than 500,000 years--older than the Boxgrove tibia, certainly--but not how much older. While the archeologists were digging, however--and finding 36 human bone fragments in all, including most of a forehead, pieces of lower and upper jaw, as well as teeth, fingers, and toes--two geologists, Josep Parés of the University of Michigan and Alfredo Pérez-González of Complutense University, were taking small samples from all the sediment layers at Gran Dolina. They were looking for a second time marker: the boundary between the Lower Pleistocene and the Middle Pleistocene. That boundary is defined as the last time Earth’s magnetic field switched directions, around 780,000 years ago. Before then the magnetic field had negative polarity: it pointed south instead of north. An earlier team of geologists had placed the switch at the very bottom of the sediment stack at Gran Dolina, far below where Carbonell’s team was digging. But Parés and Pérez had reason to believe that study had not been done carefully enough.
A couple of months after the field season, back in Tarragona, Carbonell got a call. Parés said, ‘Listen, we found negative polarity around your hominids,’ Carbonell remembers.
I said, ‘What do you mean?’
‘What I said. I’m convinced your hominids are in negative polarity. And that means those hominids are more than 780,000 years old.’
I remember very well what I told him then. ‘Listen, this is no joke. If you’re not sure, you could go down and take the whole team with you. Because that’s a strong statement. This would be the first time anyone found hominids in the Lower Pleistocene in Europe. You get the whole responsibility.’
And he said, ‘Yes, yes, okay, I’ll take the responsibility.’ And he repeated the analysis. And without any doubt we were at 780,000 years.
Sometimes the study of human evolution seems to advance at about the pace of its subject matter. Debates drag on for decades, often tediously. A hundred and forty years after the discovery of the first Neanderthal fossils, the event that gave birth to paleoanthropology, there is still no consensus on who the Neanderthals were--were they our ancestors, or another species of human entirely who vanished without a trace? The evidence lately seems to favor the latter hypothesis; just this year, for instance, DNA was extracted from one of the original Neanderthal bones and was found to be quite different from modern human DNA. But that will not end the debate. There is an irreducible subjectivity to paleoanthropology, having to do in part with the paucity of fossils, which permits arguments to remain unresolved--and nowhere is that paucity more pronounced than when you try to go back beyond Neanderthals into the Middle and Lower Pleistocene. Between the classic Neanderthals of 100,000 years ago and the earliest Homo fossils in Africa, there is a gap of around 1.5 million years that is sprinkled with just a few bones.
In the past decade the debate about Neanderthals has become part of a wider argument. The people who believe Neanderthals evolved into modern humans in Europe believe the same process happened elsewhere; modern humans evolved simultaneously in several regions of the world, they say, from populations of Homo erectus, after it fanned out from Africa. On the other side, the people who believe Neanderthals went extinct after being replaced in Europe by modern humans also believe the same process happened elsewhere; everywhere in the world, they say, premodern humans were replaced by modern Homo sapiens, which evolved only in Africa and then spread from that continent--a second migration--around 100,000 years ago. The most prominent advocate of this Out of Africa Two theory is Chris Stringer of the Natural History Museum in London. (Stringer also happens to be one of the people who analyzed the Boxgrove tibia and called it Homo heidelbergensis.) On that issue the Gran Dolina researchers are in Stringer’s camp--but their finds do not resolve the argument.
On the other hand, from the moment Aurora Martín pulled human teeth out of Atapuercan dirt, another debate ended, more or less. That was the debate about when humans reached Europe. Many people had thought, like the Nature commentator, that the settlement of Europe had not begun before 500,000 years ago. That view had been proved wrong. It was one of those rash hypotheses, unusual in paleoanthropology, that are readily falsified. The Aurora stratum, now delineated on the wall of the Trinchera by red pushpins, lies about three feet inside the Lower Pleistocene--that is, below the level of sediment where the magnetic field started pointing north, 780,000 years ago. Those three feet could have accumulated in 20,000 years or in 200,000; it is impossible to say. But the bones pulled out of the Aurora stratum in 1994 showed that human beings were at Atapuerca at least 800,000 years ago.
They did not, however, reveal who those human beings were. After the 1994 field season Bermúdez and his colleagues weren’t sure. The teeth were early Homo, and not just in the premolar roots; the tortuous, wrinkled crowns were ancient as well. But those complicated roots, Bermúdez decided after he had pondered them back home at the National Museum of Natural Sciences in Madrid, were more specifically primitive. Nothing quite like them had been described in Homo before. Homo erectus didn’t have them, or at least the erectus fossils from Asia didn’t. Bermúdez found the closest resemblance in African fossils that are more than 1.6 million years old, including the one known as Turkana Boy. That spectacular skeleton, found in 1984 at Lake Turkana in northern Kenya, by Richard Leakey’s team, is either early Homo erectus or a different and more primitive species, Homo ergaster--another unresolved debate. The Spanish researchers call it Homo ergaster, and they say it has teeth like the Gran Dolina hominids.
Primitive too was the browridge that had come out of the Aurora stratum. All browridges seem primitive to us, of course, but in their heyday they came in different styles, like sunglasses. Homo erectus in Asia had a single, almost horizontal shelf--which presumably evolved after it left Africa--that shielded both eyes. The more primitive Turkana Boy had more graceful double arches--and so did the Gran Dolina fossil, and so, interestingly enough, did the Sima de los Huesos skulls, and so did Neanderthals. Already in 1994, a line seemed to be emerging, a conceptual line, that stretched from Lake Turkana through Gran Dolina into the Sima and out again to the Neander valley. Antonio Rosas, the mandible man on the Atapuerca team and Bermúdez’s colleague at the National Museum, could trace the same trajectory. The mandible fragment that had been found at Gran Dolina was more slender-- gracile--than that of the Turkana Boy but less so than that of the Sima fossils he had studied. Even the details of its inner surface seemed intermediate.
What to call such a specimen? Who exactly were these pioneering Europeans? At that time we didn’t know what was going on, says Rosas. We were still defining our creature. So at the end of their first report on the discovery, the Atapuerca team did what Stringer had done at Boxgrove and threw their creature into Homo heidelbergensis--a commodious receptacle that already contained virtually all the Middle Pleistocene fossils from Africa and Europe, including the ones from the Sima de los Huesos. The Spanish researchers suggested that 800,000-year-old Gran Dolina Man might be primitive Homo heidelbergensis. But then, having torn through six feet of sediment to get to the Aurora stratum, they spent three Julys, 1994 through 1996, slowly sifting through ten inches of red-brown mud.
When Homo antecessor showed his face at Gran Dolina, in 1995, it was a less emotional moment than the one a year earlier. The teeth alone had established the principle of early settlers in Europe, and the face did not look all that promising. When the diggers extracted it, it was still covered with mudstone. Juan Luis Arsuaga remembers thinking that not much in the way of intact bone would survive the removal of the rock. But then it was cleaned by the technicians at the National Museum, he says. They made a miracle. The cleaning took more than a year. For Arsuaga, the moment of discovery was not when the face came out of Gran Dolina, but last December in Madrid when he first saw it for what it was.
It was only a partial face, covering the region below the eyes to the upper teeth. A few of those teeth were still in place, which allowed Bermúdez to determine it was the face of a juvenile hominid, some 11 years old--roughly the same age as the Turkana Boy. In their paper last May in Science, the Spanish workers tried to convey the impact of that face in technical terms; they spoke of the depression of the infraorbital bone surface, the marked flexion of the maxilla, the horizontality of the zygomaticoalveolar crest. But the impression Arsuaga got on first seeing the fossil was simpler: it was the shock of the new. We expected something big, something large, something inflated--you know, something primitive, he says. Our expectation of an 800,000-year-old boy was something like Turkana Boy. And what we found was a totally modern face.
The modern human face is, above all and in spite of individual variations, a small, delicate face. The modern human brain, as we are all proudly aware, is a large, bulging one. That is the story of human evolution in a few words: expansion of the brain, reduction of the face, explains Arsuaga. Work was transferred from one body part to another. With brains large enough to conceive clever tools, we no longer needed giant, powerful jaws and teeth to process our food. On the other hand, we needed room for those brains. And so forward and up they grew, creating tall foreheads that swelled over our facial features and crowded them lower on the front of our skulls. Compared with our African ancestors, our faces are shrunken, flat, and deflated. Instead of projecting forward, the bone under our eyes--the infraorbital bone surface--slopes down and backward into a depression, giving all of us, not just supermodels, hollow cheeks. (They are sometimes masked by flesh.) To connect those cheeks with our thin, projecting noses, the upper jaw--the maxilla--has to flex markedly inward. Forget about the zygomaticoalveolar crest; it’s not that important.
Until the Gran Dolina discovery, the oldest modern face was on a 120,000-year-old skull from Israel. The Gran Dolina face had all the right features, and it was 800,000 years old. It was far older than any heidelbergensis fossil, but it had a far more modern face. How could it be understood as primitive heidelbergensis? This hominid had the face of a sapiens, a mandible approaching heidelbergensis, and premolars like ergaster. What to call such an hombre? If you say it’s not heidelbergensis, it has to be a new species, says Arsuaga. And if you don’t name it, someone else will. Being of an age, 40-plus, to have had Latin forced on them in school, the Spanish researchers turned to their Latin dictionaries. Homo antecessor seemed to capture the essence of the first intrepid African who had scouted out Europe.
A new species complicates the story of human evolution in one sense, but it can also tidy things up. Certainly the scenario Arsuaga and his colleagues envision--a complement to Stringer’s Out of Africa theory-- is tidy enough. The ancestor of all humanity, in this scenario, was Homo ergaster, living in East Africa between 1.5 and 2 million years ago. Sometime during that period ergaster migrated to Asia, becoming erectus on the way. Dates that are still controversial put erectus in Java as early as 1.8 million years ago; even more controversial ones have it in China 2 million years ago. The dates are a mess, but the concept is simple: Homo erectus was essentially an Asian species. Contrary to long-held belief, we are not descended from it.
When those who would become erectus left Africa, the rest of the ergaster population stayed behind. After another 500,000 years or so of evolution, they gave rise to Homo antecessor. Sometime around a million years ago, perhaps a bit earlier, antecessor also decamped, following in the footsteps of erectus. But in the Near East it turned left into Europe, finally reaching Spain after many millennia. Why would it not have crossed at Gibraltar? Because there was no bridge, says Bermúdez. To cross the Strait of Gibraltar is difficult--the currents are very dangerous. Today people from Morocco try to get to Europe across the strait in small boats, and a few months ago there were 40 dead. He and his colleagues find it hard to imagine Lower Pleistocene hominids making the crossing in numbers large enough to establish a successful beachhead in Europe.
And it was successful, in their view: the European population of Homo antecessor gave rise to heidelbergensis, which spread all over Europe and even to Boxgrove, England. Sometime around 300,000 years ago, it was a heidelbergensis clan that chucked bodies into the Pit of Bones. Perhaps 100,000 years later, heidelbergensis had evolved, in complete isolation from its African forebears, into Neanderthals--with their large, wholly distinctive face pushing out the front of their skull and their large brain of uncertain potential pushing out the back. Meanwhile, in Africa, the populations of antecessor that had never left were embarked on a very different evolutionary path--one that eventually led to modern Homo sapiens.
After that the story is straight Out of Africa. Modern humans left that continent a little before 100,000 years ago and colonized Europe and Asia, gradually replacing Neanderthals and Homo erectus. The process took quite a while. As recently as 25,000 or 30,000 years ago, according to evidence reported last year, there may have been three species of human beings on Earth, with erectus hanging on in Java and Neanderthals in southern Spain. But those dates are still hotly debated.
As the Homo antecessor scenario no doubt will be, for some time to come. So far it has not been accepted by many of the Spanish workers’ peers. Chris Stringer, for one, still believes the Gran Dolina child is more likely to be early heidelbergensis. That species, he argues, displays anatomic traits that identify it as the true common ancestor of Neanderthals and modern humans; the evolutionary divergence between the two--which in the Spanish scenario would have begun around 800,000 years ago, after antecessor left Africa--is really less than 400,000 years old, the age of the youngest heidelbergensis fossil found. I’m just being cautious, Stringer says. There is a danger in giving a species name to everything that comes along. I’ve been accused of doing that myself--lots of people don’t believe heidelbergensis is a species.
The thing that troubles Stringer and other paleoanthropologists most about the Homo antecessor scenario is that it relies so heavily on the face of a child. Children are notorious for changing as they grow. Perhaps, says Stringer, that deflated face was strictly a juvenile feature that doesn’t distinguish antecessor from later heidelbergensis; perhaps a heidelbergensis child of the same age--none has yet been found--would have had the same kind of face. Arsuaga acknowledges the possibility that he and his colleagues could be wrong about the central evolutionary role of antecessor. It’s a big mistake being fanatical about this, he says. But he does not see that child’s face as a weakness of his story. To him it’s the best part.
What we believe, he explains, is that the modern human face represents a case of neoteny. The idea is not entirely new. In the 1920s a Dutch anatomist named Louis Bolk argued that neoteny--the retention, in adults of a species, of juvenile characteristics of an ancestor--could explain just about all of human anatomy. Bolk thought we were essentially retarded apes, arrested in our development by a simple hormonal change that had occurred during our evolution. Twenty years ago, Stephen Jay Gould tried to rescue the kernel of Bolk’s idea from this naive exaggeration--to argue that neoteny could be an important mechanism in human evolution, even if it wasn’t the main one. The child’s face at Gran Dolina, Arsuaga thinks, shows that Gould was right.
Our face, our adult face, is very small and delicate compared with the face of our ancestors, Arsuaga explains. Our ancestors had a large face, reached after a long period of growth. But our face is not a new one--natural selection didn’t work like that. If you wanted to reduce the facial skeleton, you could continue growing it until the adult morphology of our ancestors, then reduce it. But there is another, wiser way. And that is to stop the growth when it is still reduced.
What happened to Neanderthals? Neanderthals produced a face the other way. Their face is not like anything that had been produced before. They had to make a new face--exactly as we did with our braincase; our braincase is a new design--because the face they needed wasn’t on the market. So they made a new face by adding new steps to the growth process. But in our case it was easier, it was more efficient, more safe, just to stop growing the face and to retain the juvenile form. That way we got a delicate and small face--which was that of the children of our ancestors. It’s the face of the children of Homo antecessor.
To me this is most spectacular--these are the kinds of things that shake you. Finding something totally unexpected like that. Not finding fossils; finding fossils is unexpected too, and it’s okay. But the most spectacular thing is finding something you thought belonged to the present, in the past. It’s like finding something like--like a tape recorder in Gran Dolina. That would be very surprising. We don’t expect cassettes and tape recorders in the Lower Pleistocene. Finding a modern face 800,000 years ago--it’s the same thing. We were very surprised when we saw it.
Arsuaga does like find-ing human fossils, of course. But it has become a bit routine for him. Of the three leaders of the Atapuerca team, Arsuaga is the most wiry, so it is fitting that he should be the one to slither into the Sima every day in July. I’m not particularly fond of caves, he says. I just pass through to get to the site. And every day he and his colleagues slither out with dozens of bits of human bone. The bones aren’t all skulls and faces--often they’re fingertips or toe tips or even hammers and anvils from the inner ear. It was those tiny bones--bones that normally aren’t preserved even in medieval skeletons--that kept Arsuaga and his team digging through the dues-paying years of the 1980s. If those bits were there, they figured, they would eventually find the skulls and mandibles that would make their peers pay attention to Atapuerca. Anyone interested in Pleistocene hominids has to pay attention now. More than three-quarters of all the human remains found from the period between 100,000 and 1.5 million years ago have been found in the Sima. If you take as an example just the bones of the hand, there is one fragment from China and another from southern France--and more than 300 from the Sima. It is paleoanthropology as candy store, although the store is a little hard to get to.
Arsuaga and his colleagues still do not know for sure what happened at the Sima 300,000 years ago. They believe the bodies were dead when they fell into the pit because some of the bones show evidence of fatal disease. But they have found no artifacts, which makes them doubt that they are looking at the remains of a funeral rite. Perhaps the corpses--at least 32 of them and probably many more--were thrown into the pit for sanitary reasons by the survivors of some sort of disaster. Humans were part of nature, and there are cycles in nature, says Arsuaga. There are years that are good, and the animals spread, and there are years that things go bad, and the animals die in large numbers. This is what I believe--that there was an ecological catastrophe, like a drought or something. The bones in the Sima de los Huesos may all date from the same killing season, and probably from no more than two or three years.
That means they come from a single population: these people knew each other. They were all young adults and teenagers, which deepens the mystery of their death. One of them, the owner of the most spectacularly complete skull, apparently died of a bone infection that spread from a broken tooth and was probably quite painful. Another was hard of hearing, judging from the growths that blocked his ear canals. Most of them had tiny holes in their eye sockets--cribra orbitalia, as the condition is called, and it suggests they were malnourished as children. Most also had arthritic jaw joints, perhaps from grinding their molars, and they all picked their teeth enough to wear grooves in them. Finally and perhaps most important, the men and women were no more different in size than men and women are today--which contradicts the conventional view that male hunters of the Pleistocene had to be much bigger than their stay-at-camp wives to bring home the bison. It’s like we’re explorers, and we’ve met a new human tribe, a new culture, Arsuaga says. We have direct access to their lives and deaths, and we can study them as we would a modern population. A year or so ago he had an artist take all the anatomic information and paint a portrait of the Sima people, standing under a tree in happier days, as if at a family reunion.
The same cannot be done yet for the people who lived--or more likely, stopped for a while--at Gran Dolina 500,000 years earlier. Carbonell and his archeological team have analyzed the tools, around 200 of them, that were found in the Aurora stratum alongside the bones of antecessor. The tools are archaic even for their epoch. By 1.5 million years ago, before antecessor supposedly left for Europe, hominids in Africa were making so-called Acheulean tools: symmetrical hand axes, elegantly worked on both sides to produce a sharp and regular cutting edge. Homo antecessor, for reasons unknown, was stuck in the earlier Olduwan tradition. They picked quartzite pebbles out of the Arlanzón and carried them back to the cave to use as hammers; sometimes they hastily knocked big flakes off such a pebble or off a piece of flint, using the flakes as simple knives and the core as a disposable chopper to crack the bone at hand.
They cracked a lot of bones. They ate deer, bison, maybe a bit of elephant and rhino--and also human beings. Yolanda Fernandez-Jalvo, a soft- spoken young woman, now at the British Natural History Museum, who has made prehistoric butchery one of her specialties, has examined under a microscope all 86 human bones that were found at Gran Dolina from 1994 to 1996. Half of them, she says, including remains of all six individuals found at the site, display man-made marks--sharp incisions, for instance, that could only have been made by stone tools, not by the teeth or claws of a carnivore. To be sure, humans in the more recent past have been known to slaughter other humans for ritual purposes, without eating the flesh. But at Gran Dolina, says Fernandez, the human bones have been found mixed with animal bones that were cut in the same way--dismembered and stripped of anything edible. The clavicle of a four-year-old was treated in that way. If you have any respect for the person, to break the bones so heavily, to peel them--it’s looking for the marrow, which is the most protein-rich part of the body, says Fernandez. All the vertebrae are broken like that. They liked the vertebrae.
None of the bones at Gran Dolina, it seems, are from hominids who camped there; all of them are from hominids who were eaten there. Whoever did the eating left afterward and didn’t die in the cave--or at least not in the part that has been excavated. The predators could have been a rival antecessor clan, victorious in battle; they could have been members of the same family eating relatives who had already starved to death. Carbonell’s hypothesis, not widely shared at Atapuerca because there is still little evidence for it, is that it was not cannibalism at all. At Ceprano, Italy, a single braincase was discovered in 1994, just before the Gran Dolina fossils, that may be as old as those fossils, and its discoverers have called it Homo erectus. (That is controversial.) If erectus was at Ceprano, Carbonell argues, it could have been at Atapuerca eating antecessor. My big hypothesis is that there were several species of human in Europe then, he says. Always everything is in Africa and nothing in Europe! Why? That’s not logical.
The small test pit that yielded antecessor is now more than halfway down the Trinchera wall. But Carbonell and Bermúdez have started at the top of the cave again, excavating a much larger area this time, about 800 square feet surrounding the original dig. By the end of last July, the two or three dozen diggers had finished the relatively sterile layer of sediment at the top of the cave. Next July they should penetrate the sediments that date from the time of the Sima people 300,000 years ago. Carbonell is hoping to find their campsite: their tools, including scrapers for working animal skins into clothes, a fireplace, maybe even a work of art--evidence, in short, that the Sima people led complex lives, as we do. We dig to find the things that are basic to knowing ourselves, Carbonell says. That’s the whole point of this research: self-knowledge.
Getting down to the Aurora stratum again, and perhaps finding the people who ate antecessor--if that is the sort of self-knowledge we need-- is going to take a lot longer. Eleven years, Carbonell estimates. Arsuaga says, I’m impatient. We’re not going to wait till we retire. Maybe six years. Twenty years, says one of the people actually doing the digging. Whenever--Carbonell is already planning the next excavations. There were a lot of people in the Sierra de Atapuerca at certain times, he says. And I think we haven’t found the big deposits yet. The Trinchera is fragmentary. In the big caves, we’re going to find continuous sequences of occupations, and we’re going to show what an attraction the Sierra exerted. The Ebro and the Duero are the two great basins that connect all the north of Spain--and Atapuerca is right in the middle of them.
One of those big caves is a couple of miles away from Gran Dolina, at the southern tip of the Sierra and near the top of the hill. Its broad mouth, like a half-open clamshell, leads into a cool, spacious shelter. In front there is a kind of terrace, sunbathed and covered with tall grass and wildflowers, that looks out over the valley of the Arlanzón, and toward the Sierra de la Demanda in the distance. The valley has the Burgos road and a military base in it now, but 800,000 years ago--when the climate was similar to today’s--it must have been dotted with oak and olive trees and grazed by bison, deer, and elephants. Even a nomad like Homo antecessor, one imagines, would have had the sense to stop here for a while. Carbonell and his colleagues have high hopes for an excavation of this cave. They call it Cueva Mirador--which, loosely translated, means Cave with a View.