Care-Worn Fossils

Welcome to a messy tale of survival in the face of daunting physical challenges. Its protagonists include a nearly toothless adult of indeterminate sex, a man with a withered arm and one blind eye, a teenage dwarf, and a bunch of apes. No, it’s not a screenplay for the next David Lynch movie–at least, not yet. It’s a scientific inquiry into whether fossils of physically impaired individuals show that our ancient ancestors had a soft spot for the injured and infirm.

The latest chapter in this Stone Age saga began last year with a much-publicized report of a partial Neandertal jaw missing many of its teeth and marred by extensive bone damage (SN: 9/15/01, p. 167: Neandertals show ancient signs of caring). The newly discovered specimen, dated at between 169,000 and 191,000 years old, came from a man or woman who must have endured a mouthful of pain and was unable to chew food for at least 6 months, concluded coauthors Serge Lebel of the University of Quebec in Montreal and Erik Trinkaus of Washington University in St. Louis.

This person’s survival hinged on having a support system, the researchers theorized. Neandertal comrades supplied fruit and other soft foods to him or her, and they probably pounded or cooked tougher fare–meat, in particular–so that it could be swallowed without chewing.

Not everyone who stares into the jaw, which was discovered in France, or examines other disfigured human fossils sees signs of prehistoric compassion, though. Lebel and Trinkaus ignored critical evidence that undermines their conclusion, contends David DeGusta, a doctoral student in anthropology at the University of California, Berkeley.

He has examined published reports of relatively recent wild monkeys and apes that exhibit as much or more tooth loss and bone disease as that reported for the French Neandertal find, he says. Skeletal scrutiny also indicates that these animals can survive a range of illnesses and injuries that cause permanent disabilities.

Such data haven’t fueled any arguments that healthy monkeys and apes keep their disabled peers alive or to make their lives easier. Neither can such evidence be used as a signature of social support among Stone Age folk, DeGusta concludes in the December Journal of Archaeological Science.

“The French jaw doesn’t provide any evidence of increased Neandertal caregiving relative to nonhuman primates,” he says. “This fossil individual could just as easily have provided or processed his or her food without help from others.”

DeGusta, Trinkaus, and other scientists are re-examining data and specimens collected over the last century to try to clear up how Stone Age folk treated their weakened comrades.

Ancestral aid

The French jaw, found at the Bau de l’Aubesier rock shelter and dubbed Aubesier 11, joins several other debilitated Stone Age individuals often regarded as recipients of social assistance. The French jaw represents the earliest evidence of caring for the disabled by our fossil ancestors, according to Lebel and Trinkaus. It also fits with broader attempts by some anthropologists to portray Neandertals as the cultural equals of modern people (SN: 12/15/01, p. 380: Evolving in Their Graves).

“This is one more piece of the puzzle indicating that some type of social support occurred among Neandertals,” Trinkaus says.

The most prominent case of Neandertal physical impairment is an adult male whose skeleton was found more than 30 years ago at Iraq’s Shanidar Cave. Trinkaus’ 1983 analysis indicated that the Shanidar man, who lived about 50,000 years ago, suffered many bone fractures and extensive arthritic damage to his joints. His withered right arm had been paralyzed, and damage to his left eye had probably left it blind.

Moreover, several Neandertals who inhabited Croatia’s Krapina Cave around 130,000 years ago sustained skull fractures that would have knocked them unconscious and required life-saving aid from others for at least a few days, says Janet Monge of the University of Pennsylvania in Philadelphia. Monge and Princeton University anthropologist Alan Mann discovered the injuries when they recently took X rays of more than 800 Krapina fossils belonging to several dozen Neandertals.

Monge suspects that the Krapina Neandertals sustained skull fractures from pieces of the cave’s roof falling on their heads. Other researchers think that the head injuries resulted from fights using clubs or other weapons.

Some Krapina cave dwellers also lived with considerable tooth loss. It’s hard to know whether these individuals got special care from others, Monge holds. Some people today adapt to the pain of untreated dental disease and manage on their own, while others don’t. Jawbones can’t reveal telltale signs of either resilience or misery.

Neandertals weren’t the only human ancestors that survived physical disabilities. Consider three separately discovered archaic Homo sapiens fossils dating to around 150,000 years ago. One individual grew to adulthood despite an inborn misalignment of head and neck, another tottered around on a misshapen hip, and a third had bony growths in the inner ear that would have interfered with balance and walking. The discoverers of these fossil individuals have assumed that they must have benefited from some type of social assistance.

An even more curious case involved the Romito boy, an 11,000-year-old human skeleton that was excavated in an Italian cave nearly 40 years ago. This 3-1/2-foot-tall individual, about 17 years old at the time of his death, experienced a severe growth deficiency and limited mobility, according to a 1987 study directed by anthropologist David W. Frayer of the University of Kansas in Lawrence. Comrades must have taken pains to feed the diminutive teen and bring him along on periodic moves through the area’s rugged environment, Frayer’s group concluded.

Nearly toothless, diseased jaws also appear in the skeletal remains of hunter-gatherers who lived in parts of North America several thousand years ago, according to research directed by anthropologist Clark S. Larsen of Ohio State University in Columbus. In his view, however, there’s no evidence that these individuals–or the Aubesier Neandertal–received special care from their comrades.

Another anthropologist who studies Stone Age Homo species disagrees. Although it’s hard to squeeze prehistoric behavior out of fossils, Lebel and Trinkaus “are on to something,” remarks Karen Rosenberg of the University of Delaware in Newark.

Fossil evidence including the Aubesier jaw suggests that, beginning with Neandertals, social assistance of some kind enabled physically impaired individuals to survive longer than they could have in earlier species, such as Homo erectus, Rosenberg asserts.

Aping human injuries

“It’s really reaching to interpret [the Aubesier] fossil’s condition as a sign of social care among Neandertals,” contends Berkeley anthropologist F. Clark Howell, DeGusta’s academic advisor. He and DeGusta wondered whether apes, which anthropologists generally agree don’t take care of injured companions, survive after similarly serious wounds.

Although DeGusta found that relatively few researchers have probed skeletal markers of disease and injury in nonhuman primates, he located several published instances of these creatures having lived with extensive tooth loss and bone-decaying oral ailments. These reports described recently deceased animals.

One of the most thorough investigations of primate skeletons occurred decades ago. In 1956, primatologist Adolph Schultz wrote that “the misnamed permanent dentition” frequently falls out or becomes unusable because of disease in apes and monkeys, as well as in people. Schultz noted that several freshly killed chimpanzees showed evidence of having survived for months and possibly years after the loss of the majority of their teeth.

DeGusta also located a 1936 investigation by another scientist that noted near-total tooth loss in a chimp and a monkey that had lived into old age in the wild.

Studies conducted more recently have found that nonhuman primates sometimes survive not only extensive tooth loss but also illnesses such as hepatitis, malaria, and poliomyelitis, DeGusta says.

They also endure a surprising number of injuries from guns. In 1993, anthropologist Bruce Latimer X-rayed chimp, gorilla, and orangutan skeletons held at the Cleveland Museum of Natural History. He determined that about 12 percent of injuries originally classified as naturally occurring fractures were instead healed gunshot wounds. These creatures had endured types of injuries that routinely put people in the hospital and sometimes prove fatal, Latimer says.

“Even a cursory examination of great ape skeletons demonstrates that these animals have a remarkable ability to survive trauma and infection,” he holds.

The physical resilience of apes also casts a shadow over attempts to portray skeletal disease, such as that on the French Neandertal jaw, as a marker of social care. “I have no doubt that Neandertals had a sophisticated culture and social structure, but dental [disease] is not evidence of it,” Latimer contends.

That hardly settles the issue. Lebel and Trinkaus defend their position in an upcoming Journal of Human Evolution.

Wild apes and monkeys have yet to provide any evidence of having lived for long periods with as much tooth loss as that observed on the French Neandertal jaw, the researchers assert. Most of the apes and monkeys in the studies that Lebel and Trinkaus have considered had lost fewer than 60 percent of their teeth. Those who survived the most extensive tooth loss lived in the tropics where they ate soft plants, a far more congenial diet than Neandertals’ meat-laden menu, the researchers maintain.

Field observations of baboons and ring-tailed lemurs indicate that individuals that lose most or all of their teeth soon die or disappear from their groups, Trinkaus adds.

Handicapping bones

The Aubesier jaw inspires a frustrated sense of déj vu in Katherine A. Dettwyler. “Oh, brother,” she says, “will people never learn?”

Dettwyler, an anthropologist who now works at the American Philosophical Association in Newark, Del., wrote a 1991 paper that challenged fossil-fueled scenarios of compassionate Stone Age caregivers. She says that the newer evidence doesn’t change her position.

In her 1991 piece, she took special aim at scientists’ interpretation of the Shanidar skeleton. This individual may not have been a good hunter, but he could have collected plants, processed and cooked food, and performed many other daily activities, Dettwyler argued. If loss of sight in one eye occurred after adulthood, the Shanidar Neandertal could have adjusted relatively easily to a narrower visual field, she added.

Dettwyler also challenged the conclusion that the Romito boy must have been helped along on his people’s strenuous treks. Dettwyler notes that in some African hunter-gatherer groups, children as young as 5 years old walk with their mothers on long food-gathering trips. The Romito boy probably didn’t march at the head of a traveling band, but he could have straggled along on his own. It’s also possible that migrating group members left the Romito boy behind, and he then tracked them down at his own pace. There’s no way to know from his bones, Dettwyler says.

Frayer has now reversed course and agrees with Dettwyler. Because apes and monkeys show so many skeletal signs of surviving major illnesses and injuries, it’s dangerous to assume that the Romito boy or any other fossil ancestor displaying a physical disability benefited from special care, Frayer contends.

“A lot of researchers, including me, have been guilty of jumping to conclusions from fossil evidence about ancient caring behaviors,” he says.

As the mother of a child with Down’s syndrome, Dettwyler has a personal stake in this debate. Researchers who study the Stone Age and draw lessons about ancient social care from fossils rely on a handful of inaccurate beliefs about disabilities in modern societies, she says.

First, scientists assume that nonproductive individuals are rare and hard to incorporate into most societies. Instead, human groups have much experience caring for needy individuals. These include babies, children, and women in the final stages of pregnancy and the weeks after giving birth.

Second, the notion that bones inevitably tell the story of a person’s disabilities is belied by cases of blindness, deafness, mental retardation, and other impairments that don’t always affect the skeleton.

Third, people with physical disabilities often live without others’ assistance. In Mali, where Dettwyler has conducted fieldwork, many people develop disabilities from polio, leprosy, or untreated injuries. Yet these individuals can hold respected jobs, including caring for their relatives’ children, spinning cotton, and serving as traditional healers.

On the other side of the coin, even modern people who survive physical impairments haven’t necessarily been treated kindly. In Mali, Dettwyler observed some disabled individuals routinely beaten and jeered and children with crippling polio crawling to school. “The [fossil] record can’t tell us whether disabled persons were treated with compassion, tolerance, or cruelty,” Dettwyler says.

Skeleton keys

At this point, the fossil record contains just enough to keep the scientific debate about prehistoric social support simmering at a slow boil.

If skeletal keys can conclusively unlock Stone Age behavior toward the disabled, they have yet to be found, remarks anthropologist Della C. Cook of Indiana University in Bloomington. Cook studies signs of disease in skeletal remains of people who lived between around 10,000 and 5,000 years ago.

The Aubesier jaw represents a classic example of skeletal ambiguity, she says. Lebel and Trinkaus make an “interesting and persuasive” case for Neandertal social support, according to Cook. However, she notes, DeGusta provides a “useful critique” that, of necessity, relies on a small number of ape and monkey studies.

“I’m not convinced by either argument,” Cook says. “We need far more data than we’re likely to have anytime soon to resolve this issue.”

****************

If you have a comment on this article that you would like considered for publication in Science News, please send it to editors@sciencenews.org.