nullA partial skeleton of a presumed border crosser, photographed at the Pima County Medical Examiner's office in Tuscon, Arizona, was discovered in 2009 by a horseback rider in the nearby Avra Valley. Experts say this man probably died at least a year before his remains were found.

The great Sonoran Desert stretches from deep in Mexico to the middle of Arizona, a dun landscape dotted with 20-foot-tall saguaro cacti and scraggly sagebrush. With its mind-blurring heat, this is not a place where you want to be left behind—but people are all the time. Ranchers, county sheriffs, and the government patrols that guard the United States–Mexico border find them with grim regularity, the bodies of illegal immigrants who slipped across the border but did not survive the journey on the other side. Remains not found for weeks or months may amount to a few decaying bones. Sometimes an animal drags the body off, or a person strips down under the onslaught of the heat, leaving behind nothing more than a pair of worn shoes and a faded shirt.

More than 200 bodies a year turn up in the Sonoran, a number that has increased over the past decade as immigrants avoid urban areas and attempt to reach the United States by more remote routes, often through Arizona. After crossing the border, they sometimes walk 70 miles or more to reach a safe point of entry, often traveling without water and in temperatures that can reach 110 degrees Fahrenheit.

Authorities suspect that the bodies turning up inside our borders are migrants from Mexico or Central America. Their guides, popularly known as coyotes, may have abandoned them in the desert if they fell behind or got sick. “It’s hard to know what happened,” says Lori Baker, a molecular anthropologist at Baylor University in Waco, Texas, and one of the leading experts in identifying the remains. “Some coyotes just take their fees, which can be $1,500 or more, and then leave the people in the desert. Sometimes they’re dead before they even get to the border.”


For Baker, the granddaughter of a migrant worker, the issue is not whether America’s immigration laws should be tighter or looser; the issue is how to respond to the tragedy and loss. “I can’t imagine anyone’s begrudging a family an explanation of what happened to their loved one,” she says. “How do you say, ‘Sorry, I don’t want you to find out what happened to your 15-year-old son.’”

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Eight years ago, Baker realized she had the background to help. As a graduate student, she had begun analyzing and sequencing genes in 1995. Later, as a postdoc at the University of Tennessee, she developed a new method for extracting DNA from hair. Her primary goal was to study the movement of ancient peoples across the Americas, but she also consulted for the Truth and Reconciliation Commission, formed to investigate the disappearances and other political atrocities that shook Peru during the 1980s and 1990s. Baker was part of a team teaching prosecutors how to handle evidence. “I was there with quite a few international forensic scientists, and we were talking one evening about what was going on in our home countries,” she recalls. “I said we had immigrants trying to enter illegally, and quite a number died along our southern border, but it was very hard to identify them or send the remains back to their families. Everyone in the room volunteered to come to the United States to help.”

After that 2002 trip, Baker, by then working at Baylor, decided to get involved. She tapped her colleagues’ expertise and, with Erich Baker—a Baylor bioinformatics expert who is also her husband—launched Reuniting Families, a foundation that identifies migrant remains found inside the southern U.S. border. There was an enormous backlog. In 2002, when Baker set up shop, the system in place was so porous that identities were never attached to some 44 percent of the remains.

Baker’s group took a two-pronged approach: setting up a database to improve the flow of information, and bringing modern DNA forensics to bear. On the informatics end, Reuniting Families worked with the Mexican government and some of its consulate offices to integrate missing-persons reports from several databases into a single system. The migrants who die in the Sonoran frequently come from poor families “who may not have access to the Internet or even a telephone,” Baker says, but they do usually contact authorities. By collating the specifics of height, distinguishing features like tattoos, and a description of a missing person’s clothing, investigators often can make a tentative ID soon after a body is found. But only through dental and medical X-rays, finger­prints, or DNA can they be certain.