Silviu told me about how he had travelled around the countryside as a young man. He recounted how, if he’d got stuck for somewhere to stay overnight, he would find a barn and sleep in the hay. He usually looked for someone to ask beforehand, and had often been invited in to dinner. ‘People treated the occasional backpacker as a traveller: to be given hospitality,’ he said. ‘Now they want money. They think tourists have money and they want some of it.’ Silviu was worried about the people and the countryside being spoilt by tourism. He liked the wilderness.
‘What would this landscape have looked like 40,000 years ago?’ I asked Silviu.
‘I don’t know,’ he said, and paused for thought. ‘It would have been [Oxygen Isotope] Stage 3. So – colder than now. And wetter summers. Like – perhaps Norway today, at the coast; maybe like Bergen.’
I tried to imagine the hunter-gatherers in the foothills of the Carpathians, dressed warmly against the cold, in a country with red deer, ibex, wolves and cave bears. Although cave bears are long gone, there are plenty of brown bears roaming Romania today: nearly half of all European bears are in the Carpathians. Some hunting of bears goes on today; indeed, one restaurant in Bucharest even had ‘bear paw’ on the menu. There were times when I was truly glad to be vegetarian.
The following day, I visited Silviu in his natural habitat at the Emil Racovita Institut de Speologie in Bucharest. He brought a series of cardboard boxes into a lab next to his office and we carefully unpacked some of the Oase bones. There were pieces of animal bone embedded in speleothem – a real gift for a geologist like Silviu who could date the stalagmite, and therefore the bone. He also brought out a huge and formidable looking cave bear skull. And then there were the human remains: the mandible and the skull.
Again, these were quite clearly modern human. The skull was globular in shape, without any of the more obvious features of an archaic skull, like big browridges, or a protruding occiput at the back of the head. The jaw was quite gracile and modern-looking too, with a definite chin. But there were some oddities – particularly in the mandible or jawbone. The chin was very straight, the ramus (the part of the mandible ascending up to the jaw joint) was very wide, and the mandibular foramen (the hole on the inside of the ramus where the nerve supplying the lower teeth enters) was a little strange. Then there were the teeth, set in a very wide arc in the mandible, and with absolutely enormous wisdom teeth. These molars are usually smaller than the ones in front, but in the Oase jaw they were huge.1,2 I had read about these odd features in the scientific articles announcing the discovery and dating of the Oase bones, but it was something entirely different to hold the actual bones in my hands and look at them myself.
Now, everyone is unique and we all have ‘anatomical traits’ – little variations on a theme – in our bodies and our bones. In our skulls, some of us may have one hole for a particular nerve, where others have two or three. We might have little islands of bone, or ‘ossicles’, embedded in the zigzag joins or sutures where the plates of the skull come together. Some of these traits are genetic, whereas others appear during our lifetimes, and might be related to diet – or other things we do to our bodies. For instance, lumpy bits of bone inside the ‘external auditory meatus’ – the bony part of the ear canal – can be caused by swimming in very cold water. But, like skull shape and size generally, we’re not sure about how or why some of these traits occur, and the various influences of genes and environment. It’s all part of that great question in developmental biology: how are our bodies shaped by our genes and our environment?
Having said all that, however, there are traits that do at least seem to hark back to an ‘earlier’ form. If you were being unkind, you might call them ‘throwbacks’. If you were a bit nicer about it, you might think of these characteristics as echoes of evolutionary history, glimpses of where we’ve come from. And those odd traits in the Oase jaw seem to fall into this category: archaic features. But could this be more than just an echo of a more distant evolutionary past in these 40,000-year-old bones? Is it possible that, instead, the Oase bones show a mixture of modern and archaic traits because that person was a mixture of a modern and an archaic human – some sort of hybrid? This isn’t such a preposterous idea, because, when modern humans started making their way into Europe, someone else was already there: the Neanderthals.
As we have seen from the archaeology and fossil record of East Asia, ours was not the first human foray out of Africa. A series of archaic human species made the leap before us.
In a review article that appeared in Science in 2003, Ann Gibbons wrote: ‘The long-legged, relatively big-brained hominin called Homo erectus has long been considered the Moses of the human family – the species that led the first exodus out of Africa more than 1.5 million years ago.’3
The biblical analogy is great. I can imagine that striding, big-browed man leading his people out of Africa, across the Red Sea, but it’s a sleight of pen in two ways. Firstly, there’s a wry and unwritten ‘but of course it wasn’t like that’, as we all have this tendency to promote our ancestors to heroes and imagine their lives as epic struggles against adversity, winning through so that we could be alive today. And secondly, Ann Gibbons goes on to write about Homo georgicus, one of the recent and somewhat cheeky surprises in European palaeoanthropology. The three paradigm-nudging and diminutive fossil skulls were recently discovered in Dmanisi in Georgia, and dated to 1.75 million years ago. Then another small skull was found in Kenya, dating to about 1.5 million years ago – perhaps belonging to a particularly small population of Homo erectus, perhaps linked with the Georgian hominins. The Kenyan skulls were the same age as another famous fossil: Turkana Boy. This young man, with a largish brain, is sometimes classified as Homo erectus, sometimes as Homo ergaster. (Remember that the world of palaeoanthropology is interpreted differently by ‘lumpers’ and ‘splitters’ – see page 3.)
Fossils can be extraordinarily slippery when you’re trying to pin a species name on them. The Kenyan and Dmanisi skulls are no exception. They all look a bit like a small Homo erectus without browridges, but also bear similarities to another, earlier hominin species, Homo habilis. Although the discoverers of the Dmanisi skulls claim that they warrant a new species name, Homo georgicus, most researchers place the skulls in Homo erectus. So maybe erectus was the first hominin to get out of Africa after all.3
Georgia lies west of the Caspian Sea, but it is hard to know whether it really counts as part of Europe or Asia. Certainly, Dmanisi was sidelined when another, intriguingly ancient fossil, this time from the Sierra de Atapuerca, in northern Spain, was reported as ‘The first hominin of Europe’. It dated to 1.2 million years ago, and its discoverers suggested that it was Homo antecessor (a category that some lump into Homo heidelbergensis).4
By about 300,000 years ago, Homo heidelbergensis in Europe had morphed into Neanderthals. And when modern humans got to Europe, these other hominins, their distant cousins, were still around in the landscape.5,6
The first fossil of these ancient Europeans was found in 1848, in Gibraltar, but nobody paid it much attention. The bones that gave the species its name were found in 1856 in Germany, near Düsseldorf – in the Neander Valley, or Neanderthal. The valley was being quarried for limestone, and workmen clearing out mud from caves in the cliffs prior to quarrying found what they thought were cave bear bones. But a local teacher recognised that they were human and collected them up.7
The following year, rather bravely for the time, Professor Schaafhausen of Bonn University published a report on the skull and bones from the Neander Valley, saying that they were normal – non-pathological – but seemed to be from an ancient inhabitant of Europe as the remains were found alongside bones of extinct animals. This interpretation was challenged by Professor Mayer, also at Bonn, who said the bones were probably much more recent, probably those of a Russian Cossack dying from rickets who had crawled into the cave, with great browridges from frowning in agony. But a few years later the find had been widely
published, and there was a growing consensus that the bones were very ancient. The Irish anatomist William King proposed that the skeleton should be given a new species name: Homo neanderthalensis. It was the first known species of a fossil human.7,8,9
Since the discovery of the first Neanderthal fossil more than 150 years ago, several thousand bones have been found from more than seventy different sites. And there are over three hundred sites where Neanderthal stone tools have been found.
Neanderthal characteristics start to appear in European Homo heidelbergensis. For instance, the Sima de los Huesos specimens from Atapuerca, which are over 350,000 years old, already have some ‘Neanderthal’ features such as protruding faces and gaps behind their wisdom teeth, as well as a characteristic shape of the browridge, and a ridge across the back of the head: the ‘occipital torus’.10 By about 130,000 years ago, ‘classic’ Neanderthals, with full-blown features, lived right across Europe – and beyond.11 Their territory extended from Portugal in the west to Siberia12 in the east, from Wales in the north to Israel in the south. And they persisted in some parts of Europe and western Asia until less than 30,000 years ago – after modern humans had arrived in Europe.
Given that we now know so much about Neanderthals, there are still many questions about their disappearance. Although there is no evidence of Neanderthals and modern humans actually living in precisely the same places at the same time, there was certainly a period when both species were present in Europe. It used to be thought that this period of overlap lasted around 10,000 years, but new calibrated radiocarbon dates suggest that the overlap was shorter: about 6000 years in north and central Europe, and perhaps only one or two thousand years in western France.13 But why did the Neanderthals disappear? Did we kill them off or out-compete them? Or perhaps they are actually still around – could Neanderthals have been assimilated into the expanding modern human population as it flowed westwards across Europe?
There are certainly some researchers who think so. They put forward specimens – mostly skulls – like Oase and Cioclovina from Romania, the Mladeč fossils from the Czech Republic and the Lagar Velho skeleton from Portugal1 – as physical evidence for interbreeding between Neanderthals and modern humans. Palaeanthropologists João Zilhao and Erik Trinkaus suggest that archaic traits in these fossils are not just ‘throwbacks’: they may be evidence of Neanderthal genes in the early modern human populations of Europe.
Neanderthal Skulls and Genes: Leipzig, Germany
So I made my way to Germany, not to the Neander Valley, but to the Max Planck Institute for Evolutionary Anthropology in Leipzig, where I had arranged to meet Dr Katerina Harvati, who had recently analysed the Cioclovina skull. Katerina met me on the other side of the revolving door at Max Planck, and we walked into an enormous space, some three floors of atrium with light streaming in through glass walls on two sides. Stairs and ramps to the upper floors seemed to float in the air. Katerina led me up to the labs on the second floor, where she was going to show me CT scans of the Cioclovina skull.
But my attention was first drawn to a composite skeleton, put together from casts of fossil bones from different sites, standing in the corner of the lab. It was the first time I had laid eyes on a complete, assembled Neanderthal skeleton, and it was interesting to see just how stocky he looked. The ribcage flared out at the bottom, quite different from the modern human chest shape. Individual bones were generally quite similar to modern human bones, but nonetheless very rugged.
‘We can tell from their body form and proportions that Neanderthals were showing some level of cold adaptation: they were stocky, with short limbs,’ said Katerina.
But how much of an advantage would this have given them, compared with modern humans?
‘It has been calculated that the advantage would be – perhaps not as great as we originally thought – maybe the equivalent of one business suit.’
It didn’t sound that impressive. Cultural adaptations, like clothing and use of fire, must have been more important to the Neanderthals’ survival in Ice Age Europe.
But the most ‘different’ part of all the Neanderthal skeleton was the skull. Neanderthals have very long, low skulls, whereas modern human human crania are much rounder. Neanderthal faces are big: they have massive browridges, large, goggly orbits (eye sockets), large nasal openings and projecting, prognathic jaws.
So what about this Cioclovina skull that had been suggested to be a Neanderthal/modern human hybrid? The skull itself had been discovered in the cave that gives it its name in southern Romania, in 1941 – during phosphate mining – and had recently been radiocarbon dated to about 29,000 years old. The skull was really just a braincase: most of the face was missing. Although its general shape was definitely modern, some researchers had suggested that the shape of the browridge and the back of the skull were Neanderthal-like.1
Obviously, before you can confirm or reject a claim that a skull represents a hybrid, you have to have an idea of what a hybrid might look like. Is it likely to have an even mix of features from each parent? Or might it be mostly like one parent with just a few features from the other? Katerina had looked into the features of hybrids in other primate groups and she found that a common feature of hybrids seemed to be a size change – either bigger or smaller – than would be expected from the parent populations. Some hybrids – like a gibbon–siamang cross in Atlanta Zoo, and hybrids from different macaque and baboon species – looked anatomically like a mixture of the two species they came from. It also seemed that hybrid populations tended to be more variable than the parent species, and also had rare anomalies popping up more often than usual.1
So Katerina had analysed the Cioclovina skull to see if it showed any of these signs of being a hybrid: an appreciable size difference, a mixture of features, a high level of variability, or any strange anomalies. But she had also measured the skull so that she could compare its size and shape with those of other modern human and Neanderthal skulls. Describing features in skulls, even measuring them, is fraught with problems, as I had seen so vividly in China, but Katerina had also used a technically sophisticated and perhaps more objective approach to the problem of comparing skull shape and size.
The first step was to convert a real skull into a mathematical model, a cloud of points in 3D space that described the shape and size of the skull, using features or ‘landmarks’ that could be recognised on any skull. Rather than measuring a skull with calipers to get distances and angles, Katerina showed me how she had captured the 3D shape and size of skulls in two ways: using an electronic digitiser and CT scans. The digitiser was an elegant piece of equipment – an articulated arm ending in a stylus that could be placed on the surface of a skull – and points could be captured in 3D space, with x, y, z coordinates. It was a piece of apparatus that was widely used in design and engineering – and was now beginning to be applied to the study of old bones. 3D coordinates could also be taken from detailed CT scans of skulls, which would allow points on the inside as well as the outside of the skull to be recorded.
Having captured and quantified all that information, Katerina could then compare different skulls, and she did this in the context of variation among different primates.
‘The difference between Neanderthals and modern humans is not similar at all to the differences that you would find between subspecies of primates living today,’ she said.
‘It is much more similar to the distances you’d find between closely related species.’
‘So you can be absolutely sure that Neanderthals are a separate species?’ I asked.
‘Yes, that is what I’d say. They are too different to be another population or even a subspecies of modern human. They were our sister species. Closely related – but a different species.’
This seemed to refute the multiregionalist idea that all species since Homo erectus have essentially been one.
‘So what about Cioclovina?’ I asked. Katerina showed me a 3D computer model of the Cioclovina skull, based on CT sca
ns that had been done at a local hospital. She spun the model round on the screen, and pointed out the relevant features. The browridge was big, but it was broken in the middle, unlike the uninterrupted ‘monobrow’ of Neanderthals. The occipital bone at the back of the skull did bulge out, and the nuchal line where neck muscles attached was well marked, but not really Neanderthal-looking. There didn’t seem to be anything unusual about its size, nor were there any odd anomalies in the skull.
So what about the results of the shape analysis? Katerina had compared the 3D ‘landmark configuration’ of the Cioclovina skull to Neanderthal and modern human (including Upper Palaeolithic) skulls. Using different sets of statistical analyses to make the comparisons, Cioclovina always came out closer to modern humans.1
‘From my analysis, I wasn’t able to see any resemblance to Neanderthals,’ Katerina told me. ‘There is no evidence to support the claim that this is hybrid. It actually turns out to be very typically modern human in its anatomy.’
It was clear that Katerina couldn’t wait to look at the other proposed hybrid specimens, like Oase. She was open-minded about what her results meant, and what she still might find.
‘Of course this doesn’t mean that hybridisation didn’t happen. It could have happened and we just haven’t found the hybrids yet. Or, some of the other proposed hybrids that I haven’t examined yet might fit the criteria. Or it could be that it was so rare that it hasn’t left a trace in the fossil record. And the genetic evidence to date suggests that if admixture happened, it was so low that it was really not significant in an evolutionary sense.’
Indeed, it wasn’t just the shape and size of Neanderthal bones that was being studied in Leipzig, it was genes as well. In 1997, a team of scientists led by Svante Pääbo of the Max Planck Institute published the first analysis of DNA from an extinct human. They had managed to extract mtDNA from one of the original fossils from the Neander Valley. Pääbo chose to look for a non-coding, fast-mutating section of mitochondrial DNA that had already proved useful in studies into evolutionary relationships between living species.
The Incredible Human Journey Page 27