September 5, 2012
The earliest known instance of cannibalism among hominids occurred roughly 800,000 years ago. The victims, mainly children, may have been eaten as part of a strategy to defend territories against neighbors, researchers report online in the Journal of Human Evolution. The new study shows how anthropologists use the behavior of modern humans and primates to make inferences about what hominids did in the past—and demonstrates the limitations of such comparisons.
The cannibalism in question was discovered in the Gran Dolina cave site of Spain’s Atapuerca Mountains. Eudald Carbonell of the University of Rovira and Virgili in Spain and colleagues found evidence of butchering on bones belonging to Homo antecessor, a controversial species that lived in Europe as early as 1.2 million years ago. Because no other hominid species has been found in the region at the same time as the butchered bones, the victims must have been eaten by their own kind, the team concluded in 2010 in the journal Current Anthropology (PDF).
Today, human cannibalism occurs in a variety of contexts: for nutritional value (often in times of starvation), as part of funerary rituals or during warfare. The different purposes of cannibalism can leave different patterns in the archaeological record. When humans consume other humans for purely dietary reasons, the victims are often treated just like any other prey. This is what the researchers found at Gran Dolina. Eleven individuals were butchered in a manner similar to that of deer and other mammals: Bones had cut marks in areas of muscle attachments and the skulls had signs of defleshing. Thus, H. antecessor appeared to eat its own kind for a nutritional purpose—but probably not because of a food shortage, as the team says there’s evidence of cannibalism over an extended period of time, dozens or even hundreds of years.
So why cannibalism? To find an answer, the researchers looked to chimpanzees. That’s because some aspects of H. antecessor cannibalism don’t resemble those of contemporary human cannibalism or cannibalism seen in Neanderthals or early modern humans living 100,000 years ago. For instance, nine of the 11 butchered individuals at Gran Dolina were children or adolescents compared with the largely adult victims of more recent human cannibalism.
Young victims is a pattern seen among chimpanzees. When female chimps range alone near the boundary of their territory, males from the neighboring group may kill and eat the females’ infants. Carbonell and his colleagues suggest the best explanation for this behavior is territorial defense and expansion. Males may attack to scare off other chimps as a way to protect their resources and gain new land to roam; such attacks are easiest against vulnerable females and their young, which make good meals. The team likewise concludes a similar explanation may have been the motivation behind H. antecessor cannibalism.
Whether this is a reasonable conclusion depends on some unanswered questions. For example, the researchers assume that the cannibalism was the result of intergroup violence and aggression, but they offer no evidence that the H. antecessor cannibals came from a different group than the victims. If they were all members of the same clan, then territorial defense doesn’t seem likely. It also seems unlikely if H. antecessor‘s social structure was vastly different from chimps—in which groups of probably related males band together to actively defend a territory while females in a community often forage alone with their infants.
It looks like the team has some more work to do.
July 18, 2012
Neanderthals didn’t ride bucking broncos (as far as we know), but the Stone Age hominids did seem to have one thing in common with rodeo riders: injuries. In 1995, paleoanthropologists Thomas Berger and Erik Trinkaus, now at Washington University in St. Louis, noted that Neanderthals had a disproportionate number of injuries to their heads and necks. The same is true among modern rodeo riders. Just as these cowboys get too close for comfort to angry horses and bulls, Neanderthals’ hunting style—sneaking up on prey and jabbing them with heavy spears—brought their upper bodies within striking distance of large, hoofed animals.
Over the last 17 years, researchers have reassessed the Neanderthal-rodeo rider connection. Recently, in the Journal of Archaeological Science, Trinkaus offered alternative explanations for the trauma patterns.
In the new study, Trinkaus considered the injuries recorded in the bones of early modern humans that lived at the same time as Neanderthals. Early human trauma hadn’t been as well studied as Neanderthal trauma. Statistically speaking, Trinkaus saw no difference between the two species’ wounds; they both suffered a lot of harm to the head and neck. This means ambush hunting may not account for all of these injuries because humans often hurled projectiles at animals while standing back at a safe distance. Recent archaeological work indicates Neanderthals might have done the same thing on occasion. Instead, the source of those injuries might have been violent attacks within or between the two species.
Then again, Trinkaus suggests, Neanderthals and humans might not have had an abnormal amount of upper body trauma after all. He points out that even minor injuries to the head can leave marks on the skull because there isn’t a lot of tissue separating the skin and bone. Arms and legs, however, have fat and muscle that safeguard the bones against more minor flesh wounds. So, anthropologists may not be getting a good estimate of trauma to these parts of the body.
Another factor might also be masking lower body injuries—the mobile lifestyle of Stone Age hominids. Both humans and Neanderthals moved around a lot to find appropriate food and shelter. An individual who couldn’t keep up with the group, due to a broken leg, say, might have been left behind to die, perhaps in places where their bones didn’t readily preserve. (Trinkaus acknowledges that some fossils of old, sick Neanderthals have been found. But although their afflictions, such as arthritis, would have been painful, they wouldn’t have prevented them from walking.)
As Trinkaus shows, there’s more than one way to read Neanderthal trauma. But the small numbers of injured bones left in the fossil record make it hard to know which interpretation is correct.
May 23, 2012
Iraq is the home of the Fertile Crescent, the Cradle of Civilization. But the country’s importance in human history goes back even further, to the time of the Neanderthals. In 1951, American archaeologist Ralph Solecki discovered Neanderthal remains in Shanidar Cave. The cave sits in the Zagros Mountains in the Kurdistan region of northern Iraq, about 250 miles north of Baghdad. From 1951 to 1960, Solecki and colleagues excavated the cave and recovered fossils belonging to 10 individuals dating to between 65,000 and 35,000 years ago. Politics prevented further archaeological work, but the Shanidar fossils still provide important insights on the Neanderthals of West Asia. Here are a few of the most intriguing finds:
Shanidar 1: Nicknamed Nandy, Shanidar 1 lived sometime between 45,000 and 35,000 years ago. He had a hard life. A blow to the head in his youth probably blinded him in his left eye. A withered right arm and leg suggest the head injury probably also caused brain damage that paralyzed the right side of Nandy’s body. He also fractured his foot at some point. Yet his bones all show signs of healing, and Nandy lived to be a senior citizen by Neanderthal standards, dying sometime between the ages of 35 and 45. The find revealed that Neanderthals must have taken care of their sick and wounded.
Shanidar 3: Also an adult male, Shanidar 3 had plenty of problems of his own. In addition to suffering from arthritis, the Neanderthal seems to have been violently attacked. A tiny groove on one of his ribs indicates he was probably struck in the chest. A 2009 analysis (PDF) points to a modern human, Homo sapiens, as the assailant. Based on experimental stabbings of pig carcasses, a team led by Steven Churchill of Duke University determined that the most likely weapon was some kind of dart, shot from long range. Because modern humans are the only hominids known to have made projectile weapons, the researchers blamed our species for the wound. The wound may have harmed Shandiar 3′s lungs, but it’s possible he survived the attack. A callous that formed over the groove shows that he must have lived at least a few week after the incident. And modern people with similar injuries can survive even with little medical care.
Today, you can examine Shanidar 3 for yourself at Smithsonian’s National Museum of Natural History, where the fossil is on display.
Shanidar 4: Yet another adult male, Shanidar 4 was found on his side curled up in the fetal position. An analysis of the ancient pollen found in association with the fossilized skeleton revealed bright flowers had been brought into the cave. Solecki interpreted the pollen studies as evidence that Neanderthals buried their dead and adorned the graves with flowers, suggesting Neanderthals had rituals. Skeptical anthropologists say natural forces—perhaps burrowing rodents—introduced the pretty flora into the cave. Although Neanderthals might not have decorated the graves, they were responsible for burying at least some of the individuals in Shanidar.
May 2, 2012
Poor Neanderthals. Every time anthropologists acknowledge that these “brutes” were more sophisticated than previously thought, researchers come up a new reason why our closest cousins were inferior. This time it’s their lesser navigation skills. A recent study suggests that modern humans’ greater spatial reasoning may have given them an edge over Neanderthals.
Our spatial abilities is just one part of a multi-step explanation of the Neanderthals’ downfall that Ariane Burke of the University of Montreal in Canada lays out in Quaternary International. She begins with an observation. Neanderthal groups lived in small territories but moved around a lot within their home areas to find all of the food and raw materials they needed. When modern humans moved into Eurasia, they brought a new style of social organization. Different groups over an extended region were interconnected through social networks, like people today. The shuffling of people between groups helped keep group size matched to available resources, Burke argues. (How does she know these social networks existed? She suggests variation in art and other symbolic material culture found in the archaeological record is evidence of social identities, which helped groups maintain social ties.)
By living in small areas, Neanderthals may not have needed advanced “wayfinding” skills, as Burke puts it. Remembering landmarks may have been their best navigation strategy. But because humans were part of large, extended social networks—and may have frequently traveled to less familiar areas—they probably needed more generalizable spatial abilities to make mental maps of the environment. Thus, specific spatial skills may have been selected for, such as improved spatial perception and the capacity to mentally rotate objects. Burke argues that the selective pressure to improve these skills would changed the brain, “widening the cognitive gap” between modern humans and Neanderthals. In turn, improved spatial navigation enabled modern humans to quickly colonize new areas.
Burke says later Neanderthals in Western Europe might have switched to a similar type of social organization in response to a shrinking geographic range due to encroaching humans (again, this idea is based on art and other symbolic culture found at some Neanderthal sites). So Neanderthals might have been on a path toward better spatial reasoning and enhanced cognition. But it was too late. They couldn’t keep up with modern humans.
This scenario reminds me of a study published last year on human and Neanderthal ranging patterns. It came to a different conclusion about the Neanderthal extinction. According to a team led by Michael Barton of Arizona State University, Neanderthals and humans both lived in nomadic groups that roamed over small territories. But as climate changed and resources became sparse, both species started to set up base camps and make longer but more targeted trips across the environment to find food. Because Neanderthals and humans were traveling over greater distances, they met each other more often and probably mated more. Under this scenario, Neanderthals eventually died out because they blended into the human population. This wasn’t because humans had superior intellect of any kind—their numbers were just greater and that’s why they took over. Barton’s team came to these conclusions by looking at changes in patterns of tool-making over time.
I’m not in a position to say which explanation is right. Maybe neither is. But it’s fun to think about the Neanderthal extinction in new ways.
November 22, 2011
A popular explanation for the disappearance of Neanderthals is that modern humans were superior, evolutionarily speaking. Our ancestors were smarter and more technologically advanced. When they left Africa and populated the rest of the world, the Neanderthals didn’t stand a chance.
But what if Neanderthals went extinct in part because they were too successful? New research published in the journal Human Ecology demonstrates how that’s possible. By adapting their behavior to the challenges of climate change and expanding their ranges, Neanderthals may have set up the circumstances that led to their demise.
Neanderthals emerged in Europe and West Asia by 200,000 years ago. Their close cousins, Homo sapiens, arrived in that territory sometime between 50,000 and 40,000 years ago. Within a few tens of thousands of years, Neanderthals were gone. The timing of our arrival in Eurasia and the Neanderthal extinction has led paleoanthropologists to conclude the two events are related.
Archaeologist Michael Barton of Arizona State University and his colleagues developed a new approach to studying the Neanderthal extinction, by looking at changes in land-use patterns in both Neanderthals and modern humans. They first examined 167 archaeological assemblages from across western Eurasia, from Spain to Jordan, and as far north as Romania. All of these sites date to the Late Pleistocene, 128,000 to 11,500 years ago. The team identified which species lived at which sites based on the type of artifacts; Neanderthals and humans made distinct types of stone tools.
At the beginning of the Late Pleistocene, the team discovered, both Neanderthals and modern humans tended to be nomadic, moving their camps from site to site to utilize different resources in different places. As climate became more unstable and unpredictable over time, it was harder to find resources, so both species changed their behavior: They began to travel over a larger geographic area. But instead of moving to new sites more frequently and lugging all of their stuff across greater distances, they maintained more permanent base camps and took longer, more targeted hunting and foraging trips, returning home with their bounty.
These different hunting-and-gathering strategies left their mark in the archaeological record. When Neanderthals or humans moved their camps more frequently, they tended to repair and use the same tools over and over again because it was easier to carry around fewer tools and recycle them than to bring along raw tool-making materials everywhere they went. Therefore, in archaeological sites that record nomadic behavior, archaeologists find more stone tools that have been reworked and fewer stone tools overall compared to sites that were used as more permanent base camps, where researchers find an abundance of stone tools that show little sign of being reused.
Finding that this change in behavior correlates with climate change is fascinating in its own right, but there’s another implication that relates to the question of the Neanderthal extinction. Because both humans and Neanderthals started to stray farther and farther from home to find food, they had more opportunities to come into contact with each other—more chances for mating.
In other types of animals, the researchers note, species sometimes go extinct due to breeding with closely related species, or hybridization. If one species has a larger population than the other, the less numerous species will sort of blend into the larger species. As more and more interbreeding occurs, the smaller population will eventually disappear. This may be what happened to Neanderthals, according to two population models that Barton and his colleagues developed. Under these scenarios, humans didn’t have to be better adapted to the environment (physically or culturally) than Neanderthals to win out—they just had to be more numerous. “In one sense,” the researchers write in their report, “we could say that their extinction was the result of Late Pleistocene globalization.”
Of course, it is possible that humans were more numerous and had evolutionary advantages over Neanderthals. That’s a question that requires more research and more sophisticated models. But it’s interesting to think that the Neanderthals may have sealed their fate by adapting their ranging behaviors to the changing climates of the Pleistocene. In that sense, they may have been too successful for their own good.