How Bioarchaeology Works

It would be easy to get swept up in the broad intellectual scope of bioarchaeology, but what it all comes down to is this -- the bones. Human bodies are notoriously fragile in the face of decomposition. When we die, our flesh quickly degrades due to environmental conditions and microbes that feed on our remains.

For the most part, our hard, durable skeletons are all that's left of us, and even those begin to break down over time. So bones, in essence, become centerpieces of evidence as bioarchaeologists work to unravel mysteries about ancient peoples.

Some places are better than others for unearthing bones. Bioarchaeologists work all over the planet, but they often prefer parts of the world where human remains are best preserved. Corpses that wind up in very dry or very cold or airless locations may last for centuries with relatively little decay. The arid areas of the southwestern United States, Andean South America, Egypt, and frigid parts of Europe are hot spots for bioarchaeology because many human remains can be found there in relatively good condition [source: Turner].

Dr. Bethany Turner, assistant professor of anthropology at Georgia State University in Atlanta, Ga., says that choosing bioarchaeological research locations isn't just weather-related.

"Some of these areas are also popular because there is already a lot of rich archaeological knowledge about them, which can help bioarchaeologists structure more in-depth hypotheses and ask questions with their research that are grounded in historical context."

In these well-established locations, scientists can easily share knowledge and develop their theories about past peoples. With plentiful bones as the basis for their ideas, researchers can forge ideas about how human populations developed, thrived and suffered, and overcame or succumbed to environmental or social upheaval.

No matter where on the planet the research takes place, uncovering the stories that bones have to tell is painstaking work. Sometimes those skeletal stories convey details that no one, not even the scientists, could have imagined.

Reconstructing ancient societies requires meticulous work, especially for bioarchaeologists, who must balance aspects of biology, archaeology and culture. These scientists are getting better at creating a more comprehensive understanding of skeletal and dental remains, both of which tell stories in and of themselves.

To experienced eyes, bones are full of clues about the life of a human being. A bioarchaeologist can usually determine the sex of an individual due to differences in male and female anatomy. Cranial and pelvic attributes, for instance, often help sex a skeleton. But there's a lot more to learn.

Human bones are noticeably affected by the physical burdens they bear in the span of a lifetime. A sedentary lifestyle can lead to loss of bone mass. The bones of a person who does a lot of hard labor, though, are often stronger and bigger.

A bioarchaeologist might combine established knowledge of an excavation site with these kinds of bone-based clues to hammer out a more holistic understanding of a society. For example, if the bones came from a burial ground of people who were understood to be poor laborers, saddled with the hardest work of their society, it would make sense that their bones reflected their lifestyles.

And if a nearby grave belonged to a person of higher societal stature, those bones might tell a very different tale. Perhaps the bone density is much lower, indicating a life with less physical stress. Taken as a whole, a bioarchaeologist can use such clues to generate ideas of what the political and cultural climate of the time might have been like, including labor disparities.

Dental clues also tell an ancient person's story. When children suffer from malnutrition or a serious infection causing fevers or diarrhea, it often disrupts the formation of the hard enamel that protects their teeth. During periods of insufficient nutrition or disease, lines form in the developing teeth; the size and shape of those lines can indicate how long a person may have suffered from a lack of food or an infection. Because these lines never go away, bioarchaeologists can study childhood health even in people who died in old age. In addition, tooth decay can point to greater consumption of starchy carbohydrates. This is because humans have oral bacteria that feed on carbohydrates, and, as a side effect, also break down human teeth more.

Many of these bone and dental clues are detected visually. But innovative technological advancements can also help scientists discern the tales that bones have to tell, as you'll discover on the next page.

Bioarchaeologists employ several modern technologies to aid their work. X-rays, for example, find details in both structure and damage in bones and teeth.

Scientists can reconstruct diet using techniques such as stable isotope analysis. For example, they might use a mass spectrometer to vaporize samples, which break down into various isotopes, or particles of an element that differ in their molecular weight. The ratio of heavier particles to lighter ones for the same element helps determine what sort of carbon or nitrogen a person consumed in his or her lifetime. A high ratio of nitrogen isotopes can point to a meat-heavy diet; a high ratio of carbon isotopes can indicate consumption of plants like maize or sorghum, while a low ratio of carbon isotopes can indicate consumption of other plants like potatoes or wheat.

Genetics is another high-tech way to analyze population histories. DNA from human remains can be used to determine the sex of individuals, genetic relatedness and can even be used to infer marriage patterns. Ancient DNA can also be combined with analyses of other isotopes, from elements like strontium, oxygen, and lead, to investigate prehistoric population movements.

With ancient DNA, researchers might establish different lineages within a burial ground. That kind of information -- matched with other knowledge about grave monuments, burial orientation and corpse handling -- assists them in building a story about the social organization of an ancient population.

For example, a grave filled with all sorts of goodies and treasures, or with a bigger monument or marker, near others that are relatively barren, suggests preferential handling of a person perceived as more important in a society. These signs are indicators of a culture that recognizes differences in status. That kind of information can help scientists reassemble a societal hierarchy. Similarly, a grave that has a skeleton with isotope ratios that suggest a different diet, different birthplace, and with different goodies and treasures than nearby graves, suggests a foreigner who immigrated to the population. Scientists can take that kind of information to reconstruct a societal hierarchy.

As they develop their knowledge bases and expand our understanding of ancient civilizations, bioarchaeologists sometimes encounter resistance. Click over to the next page to find out why some people aren't too keen on scientists sifting through their ancestors' remains.

Not surprisingly, bioarchaeological research sometimes stirs up ethical and legal issues; specifically, respect for the dead and items of cultural heritage. To address these concerns, the United Nations Educational, Scientific and Cultural Organization (UNESCO) adopted a convention on the Means of Prohibiting and Preventing the Illicit Import, Export, and Transfer of Ownership of Cultural Property in 1970. Broadly, this convention attempts to prevent the abuse of remains and the illegal sale of cultural objects.

Many countries, such as Switzerland, Japan, Australia and others have created similar types of legislation in hopes of protecting important cultural finds. In 1990, the United States passed legislation called the Native American Graves Protection and Repatriation Act (NAGPRA).

The act compels federally-funded institutions, such as museums, to return Native American artifacts like skeletons and sacred items to descendants or associated Native American tribes. More specifically, objects that are part of "cultural inheritance" are subject to return. These kinds of objects belong to the tribe as a whole and cannot legally be sold or given away by an individual.

In early 2011, the Tlingit Indians of Alaska wielded this legislation to recover an elaborate headdress from the Virginia Museum of Fine Arts. In the same year, the Choctaw Nation of Oklahoma initiated an effort to take back and rebury 500-year-old remains that were excavated during construction of the Natchez Trace Parkway, which was built in the 1950s and '60s.

But not everyone agrees with NAGPRA's aims. The law specifies that federal officials need to communicate with Native American religious leaders if they assert a claim to cultural objects. Some opponents say that NAGPRA, in effect, incorporates Native Americans' religious beliefs into federal law.

Also, NAGPRA allows Native Americans to use oral histories as evidence for claims. This is troubling to some researchers, who say that this stipulation can be applied to wrongly claim items or remains.

Fortunately for the scientific community, most bioarchaeologists support NAGPRA and its ethical mission, and find that it does not impede the work that they do. In fact, many bioarchaeologists work directly and in partnership with descent communities to make their research both ethical and meaningful to descendants. So long as the work is executed respectfully, many people understand that bioarchaeologists' work can help us gain a better sense of what our own culture is all about.

It's often said that historians write history -- and frequently, historians fixate on rich and famous people. But this kind of perspective doesn't tell much of the real story of ancient cultures and societies.

Anthropology professor Turner says that's why bioarchaeology is so important -- it attempts to show more of the reality behind our past.

"Bioarchaeology explicitly operates from the bottom-up, looking at the masses of people who weren't always included in historical writings or iconographic images. We are fascinated by the lives of everyone at every tier of a society, so we bring to the table a much richer and more inclusive perspective on both ancient and historical peoples."

Turner adds that bioarchaeologists also study historically marginalized groups within these ancient contexts. For example, researchers may focus on women, prisoners of war or people from a lower socioeconomic class, so that their places in history are better understood.

More expansively, this research clarifies the experiences of our ancestors over a wide range of time periods and geographic regions. We also better comprehend nutrition and diseases in historical context, see insights into population growth and population movement, and discern declines in human numbers due to disease or conflict.

Those kinds of details and stories are relevant to contemporary people. "By understanding earlier societies, we are better equipped to understand modern ones as well," adds Turner. By unearthing new knowledge, bioarchaeologists not only establish a better understanding of what happened to ancient peoples, they ultimately create a clearer picture of what exactly makes us human.