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Closer to us than we thought

Research carried out by a team of Spanish paleontologists at a cave in Asturias adds to the growing consensus that Neanderthals and Homo sapiens interbred

Days before, sitting in front of the fire, the patriarch of the Neanderthal group that Ida had joined made a hard decision. It had been weeks since they had found any food, the cold was making things harder, and several in the group had already perished from hunger. The times when they had fed the fire with the bones of their prisoners seemed far away, when they had eaten roasted meat and fat, and told stories as they warmed themselves.

The women and children were the first to die. They had been buried behind rocks at the back of the cave. Ida was 20 years old, with red hair and blue eyes. She already knew what it was like to lose a loved one: several months earlier, before joining the clan, she had buried her father, placing a giant reindeer antler on his grave. She had cared for him for the 10 years since a bear had left him partially paralyzed. Now more and more of the clan were dying, and so the patriarch decided that they should nourish themselves by eating the dead.

She had buried her father, placing a giant reindeer antler on his grave

Spain has some of the most important Neanderthal sites in Europe

"We who live outside Africa carry a little Neanderthal DNA in us"

They ceremoniously dragged the bodies to the cave's entrance, and skillfully began to butcher them. Using axes and flint knives, they removed the meat from the bones, sometimes breaking the bones to get at the marrow. Ida satisfied her hunger, but noticed that a collective evil had spread throughout the group, like some demon from a dark corner of the cave. The patriarch was the last to die. Ida felt that something malignant and invisible had taken over the cave, and that she would die if she stayed there.

After provisioning herself with the patriarch's own flesh, Ida set off to the south. Her father had taught her how to forage for plants. She found some herbs in the grasslands, and she found seeds that she could eventually boil down to make a delicious paste. She also knew how to make glue from the resin that seeped out of the trees.

Ida made her way to the coast, and joined another group. They were cooking something delicious that tasted of the sea. They roasted the meat of a strange animal with horns that dragged itself along the beach. In the following days, Ida accompanied the men to learn how they hunted. They would hide behind rocks, waiting for the mother to leave her young ones. Two men would jump out and drive the infants into the knives of the others in the group.

Ida also learned how to make necklaces out of shells, painting them red with a dye. The men and women of the group painted their faces and bodies. Sometimes they would walk long distances to make contact with another group who were taller, thinner and less strong. Ida, who was less than 1.5 meters tall, singled out the tallest of the new group, and soon after decided to mate with him, just as she had seen other women in her father's clan do.

Ida's story could have taken place around 50,000 years ago anywhere in what today is Spain. This country has produced some of the most important Neanderthal sites in Europe, the most recently discovered of which is Palomas in Murcia, on the Mediterranean coast. A team led by anthropologist Michael Walker has just uncovered an exceptionally well-preserved skeleton of a woman who would have lived around 50,000 years ago. Walker says that most of the bones are still anatomically connected. "We haven't seen anything like this for 35 years. We dug her up as though she had been buried in a cemetery," he says.

Neanderthals have until now been scorned as clumsy, idiotic brutes with little in the way of developed culture. But our pitiless modern view of Homo neanderthalensis may be tempered by new findings that provide insight into the terrible life our evolutionary cousins faced. Recent research shows that Homo sapiens and Neanderthals have a shared past.

Neanderthals had different skeletons and morphology: they were tougher, stronger and significantly shorter, with a marked brow and a bigger cranium and brain. "Many of the features that we use to distinguish between modern humans and Neanderthals are anatomical details that are not visible externally," says Portuguese paleontologist João Zilhão, who works at the Catalan Institute for Research and Advanced Studies in Barcelona. He believes that Neanderthals were as "human" as us, and that they have as much in common with us as a pygmy does to an Eskimo. He illustrates his argument by pointing to Russian wrestler Nicolai Valuev, whose appearance is Neanderthal-like, "but he is within human variability." In short, says Zilhão, the question isn't about how different Neanderthals were to us, but how similar.

Over the last 20 years, a cave in Asturias known as El Sidrón has yielded invaluable clues in the form of bones and other material, providing us with a unique insight into how Neanderthals lived. A team led by Spanish paleontologist Antonio Rosas of the CSIC science council has analyzed the remains of 12 individuals, which are thought to represent three adult males, three adult females, three male adolescents, two juveniles and an infant of unknown gender. The team found marks on the bones that show they were likely the victims of cannibalism.

All El Sidrón individuals suffered from developmental stress, or periods of growth arrest, presumably arising from malnutrition. This is indicated by deficiencies in dental enamel, present on over 50 percent of the group members' incisors, canines and premolars, and over 30 percent of their molars. Five of the members had experienced two such episodes of growth arrest and one adult had experienced four. It is clear that for this extended Neanderthal family, life was very difficult - and in the end, it seems, they met a grim fate.

Systematic excavation at El Sidrón began in 2000, and around 1,800 skeletal fragments and 400 stone tools have been recovered to date. The latter include side scrapers, denticulate pieces, a hand axe and several points. A group size of 12 individuals at El Sidrón is reasonably consistent with a previous estimate of between eight to 10 individuals per Neanderthal group, based on the size of sleeping and combustion activity areas in the long-occupied rock shelter of Abric Romaní, near Barcelona. However, because the original external deposit cannot be studied, it cannot not be ruled out that the El Sidrón group was larger and that some original members are not represented among the remains.

The tools and remains were found in a side gallery deep within the cave complex, and the trove was probably introduced into the cave from the surface when a violent storm caused an upper gallery or a series of fissures to collapse. Pebbles and clay were also dragged down from the surface. Around 18 percent of the tools have been refitted, suggesting that they are all the same age and that the associated human remains represent all or part of a contemporaneous social group of Neanderthals, who died at around the same time.

The low temperature of the side gallery meant that genetic material has survived and mitochondrial DNA has been extracted from each of the individuals. It was found that all three of the adult males carried the same mitochondrial lineage, but the three adult females all carried different lineages. Mitochondrial DNA is not a part of the primary genome and is inherited solely from the maternal line. The implication, therefore, is that the males shared the same maternal lineages but the females all came from different origins. This suggests that in Neanderthal groups, mature males remained within their family birth group, but females came from outside. Patrilocality, as it is known, is present in about 70 percent of modern human societies, where men remain in the family home but women move to the home of their new husband upon marriage.

Rosas says that Neanderthal groups frequently exchanged women to preserve genetic diversity. "It was very common in hunter-gatherer groups. We are talking about small groups, a low number, maybe between eight and 30 people, and with a certain degree of mobility. If these groups didn't mix with others, then within 10 generations there would have been genetic and cultural deterioration. The practice also helped to establish links between groups."

Paleontologists agree that there is no evidence to suggest that Neanderthals were violent. The most likely explanation for cannibalism is hunger, says Rosas. The belief that Neanderthals like Ida felt compassion, and looked after relatives who were no longer of any use to the group, is borne out by other finds. Perhaps the most spectacular is the so-called Old Man of Shanidar, whose remains were found in a cave in Iraq. He had terrible wounds on his arm, both legs were deformed, and he had been hit hard on the head as an adolescent, leaving him almost blind. But according to anthropologist Penny Perkins of the University of York, and author of The Prehistory of Compassion , he could only have lived for as long as he did with the support of his group.

Far from being the brutish, raw-meat-eating hulks as they have typically been portrayed, Neanderthals ate a relatively varied diet, and cooked their food. They were masters at making fire. Archeologist Eudald Carbonell has identified at least a dozen categories of fire making at the Abric Romaní site, used for example for cooking, heating, or lighting. Anthropologist Amanda Henry, who has excavated extensively at the Shanidar cave, has identified seeds from fruits such as dates, wild wheat, oats and legumes such as barley and lentils in the teeth of Neanderthals.

"All we can deduce is that they cooked with water, presumably boiling their food to roast it," says Henry. "We don't know how they did it; presumably they had a variety of receptacles made of some kind of organic material, although we have found no evidence yet. What we do know about their cooking comes from ethnography. We can compare what we have found at Neanderthal sites with what we know about existing hunter-gatherer societies. But what we have yet to find at Neanderthal sites are the stones that would transfer heat from a fire to receptacles."

Our fictitious Ida had eaten human meat; surely this makes her more primitive than Homo sapiens? This is one of the most enduring myths about Neanderthals. In reality, 50,000 years ago, many human tribes practiced cannibalism. In fact, eating each other is one of the defining traits of humanity. "If they resorted to cannibalism due to lack of food, or for ritual reasons, then that makes them more human, not less," says João Zilhão.

Ida joined a group living on the coast, who were able to capture dolphins and seals. Remains of whale and seal bones have been found in caves near Gibraltar. Anthropologists speculate that without nets, Neanderthals probably killed young seals while their mothers fished, and scavenged for beached whales or dolphins. Neanderthals, then, used complex hunting methods. Add to this the ability for abstract thought plus an understanding of symbolism and a sentient being similar to ourselves emerges. Recent work by Zilhão and his colleagues show that Neanderthals adorned themselves and painted their caves. Two caves in Murcia - Los Aviones and Antón, five and 80 miles inland respectively - provide solid evidence that Neanderthals had a decorative side to their nature.

"We found pierced conch shells there that had been painted. They have no other function than to adorn. In the Los Aviones cave we discovered complex mixes of pigments, made up of different minerals, the aim of which were to achieve supernatural effects," says Zilhão.

All of this took place 50,000 years ago, before the first modern humans came into contact with European Neanderthals. It is generally accepted that the first contact between the two took place around 40,000 years ago. Which means that 10,000 years earlier, Neanderthals were already painting their bodies and dwellings. Zilhão says that accumulated prejudices blinded scientists to the evidence before their eyes. The first such examples were found in the 1950s in France, but it wasn't until a decade ago that the scientific community began to accept that the sophisticated decorations and adornments they had found belonged to Neanderthals, and not Homo sapiens.

In our story, Ida mates with a Homo sapiens. This is an issue that still divides the scientific community. Some argue that modern humans are a biologically separate species; although everybody accepts that humanity was born in Africa, Homo sapiens pushed the Neanderthals out of Europe and western Asia, where they had lived for 200,000 years. We were at war with them. We had better technology and eventually we drove them to extinction around 30,000 years ago. There are no Neanderthals left, but perhaps there of traces of them in our gene pool.

João Zilhão and Erick Trinkaus, a paleontologist at Saint Louis' Washington University, argue that Neanderthals and Homo sapiens bred. They cite a skeleton found in Portugal in 1998 of a child that died some 24,000 years ago, and which had Neanderthal features. Skeletons have also been found in Romania and the Czech Republic with similar mixes between modern humans and Neanderthals. Zilhão says that the process of contact and assimilation took place over some 37,000 years, and that it is therefore impossible for Neanderthals - at least Neanderthals that were not mixed with Homo sapiens - to have been in Gibraltar between 28,000 and 30,000 years ago, as has been claimed.

Last year, researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig analyzed some four billion base pairs of DNA from Neanderthals. Analysis of the resulting genome sequence draft showed that Neanderthals left traces of themselves in the genomes of some modern humans. "The comparison of these two genetic sequences enables us to find out where our genome differs from that of our closest relative," research team leader Svante Pääbo said in a statement at the time.

The DNA fragments came from bones found in Croatia, Russia, Spain and the Neanderthal region of Germany. But the scientists had to develop a new method of separating DNA microbes that had lived in the bones for some 40,000 years and the DNA of the Neanderthals themselves.

"Over 95 percent of the DNA in one sample originated from bacteria and micro-organisms which colonized the Neanderthal after his death," Pääbo said.

Once they were able to compare the human and Neanderthal genome sequences, they discovered that, contrary to the common belief that the two species are not related, it appears the two actually bred enough for traces to appear in between one and four percent of modern human DNA. "Those of us who live outside Africa carry a little Neanderthal DNA in us," Pääbo said.

The scientists compared the genome sequences for Europeans, Asians and Africans against the Neanderthal, and found that humans outside Africa show traces. "Neanderthals probably mixed with early modern humans before Homo sapiens split into different groups in Europe and Asia," Pääbo said.

But Eric Trinkaus wasn't surprised by the discovery. "The genetic tests don't prove anything," he says. "We knew already; the geneticists have simply provided the evidence. We have a number of modern human fossils that show a certain Neanderthal ancestry, even if they are modern humans. As the modern humans spread out over a wider area after 50,000 years, they came into contact with Neanderthal communities. We know from archeology that they had much in common, and it is likely that the two would have cross-bred. It probably took place over different periods in different places," he says.

So if there is a little bit of Neanderthal in us, how is it possible that two different species were able to produce fertile offspring? Trinkaus says that two species that are sufficiently close can produce fertile offspring, but whichever is more dominant and numerous will absorb the other. "In North America there are two species: the coyote and the wolf. Under normal ecological conditions, they behave like two separate species, competing with each other and not breeding. But if the ecological balance is disturbed, then males and females from both species will mate, and produce fertile offspring. The red wolf, which lives in the southwestern United States, is a hybrid of the coyote and the wolf," he says.

Trinkaus says our reluctance to own up to our Neanderthal past has nothing to do with biology, or the idea that they belong in the remote past, but simply that we see ourselves as special. We are separate from every other species on the planet, and the same must apply to Neanderthals. "When we published the results of the Lagar Velho find in Portugal 12 years ago, some people responded positively to our interpretation that the child was a mix of Neanderthal and Homo sapiens." Trinkaus believes that the simplest explanation for the evidence is that there was cross-breeding between Neanderthals and Homo sapiens. "Many of those who disagree with the scientific evidence do so on the basis of philosophical arguments. We are talking about the origins of humanity, and the place we occupy in the world. If you look at it from a scientific perspective, or if you do so from a religious one, you have to accept that there is a certain prejudice toward one answer or the other."