Bruce Anderson, a forensic anthropologist at the Pima County Medical Examiner’s office, was already on the job—and getting overwhelmed by the steady flow of bodies and clothing and bones—when Reuniting Families was formed. His office was handling medical and dental records and fingerprints, but DNA analysis would add a crucial missing piece. After Baker got started, Anderson quickly reached out.
Today, as soon as Anderson sends Baker a bone, she begins the arduous process of extracting DNA. First a sample is purified under a sterile hood to eliminate contaminants, especially foreign DNA. Then Baker takes 250 milligrams of the bone (about 0.01 ounce), grinds it into a powder, and uses silica to separate all the other biomolecules from the pure DNA.
With her up-to-date equipment, Baker is usually able to isolate nuclear DNA, the genetic material inherited from both mother and father and unique to each individual. But about 10 percent of samples are so degraded that all she can recover is mitochondrial DNA, which is more abundant but less specific. Passed down through the mother alone, mitochondrial DNA cannot distinguish an individual, though it can identify someone as part of a group. When Anderson has a bone sample from someone he thinks he can identify but wants to know for sure, he asks the consulate to send saliva or blood samples from that person’s family for Baker to analyze. But even after all that effort, half of the hundreds of cases Baker works on each year end without resolution.
To improve the odds of recovering an identity, Baker has looked to other techniques. One of them involves using her skills as a forensic anthropologist to make a genetic map of Mexico so that even heavily degraded genetic remains can be compared with regional populations to get an idea of where they came from. In a complementary project, forensic anthropologist Kate Spradley of Texas State University is digitizing the shapes of skulls of the dead to get a better grasp of which regions correspond to which specific shapes. Investigators tend to lump most remains into the broad umbrella group of “Hispanic,” but Baker says that in fact, skulls from Mexico, Guatemala, and Peru are all different.
When combined in a database, this kind of information is shedding light on the living as well as the dead. Baker has found that an overwhelming 94 percent of the recovered remains belong to indigenous people for whom Spanish is a second language. Indigenous Amerindians may be more likely to head north because they often live in relative poverty in their native countries, she says; they also may experience prejudice because of their darker skin. These are the direct descendants of the people who settled the Americas after the last Ice Age—the same people Baker sometimes studies in her work with ancient bones.
“I’d rather do DNA extractions on a 17,000-year-old bone because there’s no emotional attachment,” Baker comments. Not long after establishing Reuniting Families, she considered dropping her effort to name the border dead. Then came the case of Rosa Cano in June 2003. A single mother, she had set out to find work in the States. When weeks went by without a word, her mother (also named Rosa) contacted authorities, who put her in touch with Baker. It turned out that DNA from the bones Anderson sent to Baker matched a DNA sample from the family. “I had just found out I was pregnant with my first child,” Baker remembers, “and trying to imagine this mother finding out that her own child had died? It broke my heart.”
Months later, Baker’s friends visited Cano on Baker’s behalf. “Rosa went running up to them,” she says. “She thought my friend was me and started hugging her, saying, ‘Thank you, doctera. Thank you, doctera.’” The woman sent Baker a traditional Mayan dress that she had made by hand. Rosa said that knowing what happened to her daughter made the loss easier to deal with. “The hope eats you alive every day,” she told Baker’s friend. Baker decided to carry on.