ARIVACA - As the white SUV turns onto a rural dirt road, Jason De León spots something on the ground.
"Wait, turn back," the 36-year-old anthropologist tells his co-worker, Cameron Gokee.
The sun has just come up and there's enough light to spot a pile of backpacks and a green jacket at the side of the road.
De León pulls clear plastic bottles from the bags. A yellowish liquid sloshes inside. "It looks like cattle-tank water," he says.
Tire and horse tracks are nearby, and so is a piece of black string like the kind Border Patrol agents use as temporary handcuffs.
Some may look at the scene and see trash. To De León, this is American history in the making.
Since 2009, he has led different groups of students from across the country and even Canada through the Sonoran Desert to study unauthorized migration using archaeological and anthropological methods. The project has collected and cataloged more than 10,000 artifacts left along the way by those trekking the desert.
He can usually tell how old the site is or how far the migrants walked by the objects found. For instance, black shoe polish tells him it's an older site from a time when migrants painted their water bottles to attract less attention. Now, they buy them already black.
De León, an assistant professor of anthropology at the University of Michigan, said he started the Undocumented Migration Project to document history and to get a fuller picture of what's happening.
"Undocumented migration is a complex phenomenon," he says. "I want to provide reliable information to help the public see behind the curtain."
Half of the research is done by walking the same trails migrants use. The other half is spent talking to border crossers staying in the migrant shelters in Nogales, Sonora, or getting ready for their journey in the town of Altar, Sonora.
Over the years, migration through Arizona has slowed, but researchers don't know how much of that is due to border enforcement and how much to the recession.
When De León started the project, it was common to find football field-sized sites with hundreds of tattered backpacks, sardine cans and plastic water bottles.
As immigration enforcement intensified in San Diego and parts of Texas in the 1990s, the traffic flow shifted to Arizona - where officials thought the harsh conditions of the desert would serve as a natural deterrent.
Until recently, the Tucson Border Patrol Sector was the busiest in the country. But then apprehensions started to pick up in South Texas. So far this fiscal year, 99,177 people have been apprehended in the Tucson Sector, compared with 108,195 in the Rio Grande Valley Sector.
But people are still crossing Arizona's harsh desert. Increasingly, they come from indigenous communities in southern Mexico and Central America, De León said.
"These are some of the poorest, least-equipped migrants to undertake one of these crossings," De León said.
Students get credits
With record deportations, there's also a growing number of people who lived most of their lives in this country before being sent back to their birth countries and are desperate to return to their lives in the United States, he said.
Now people walk in smaller groups for up to 10 days and through more treacherous and mountainous terrain to avoid detection.
To reach the sites where border crossers rest or pray, students have to bushwhack five or six miles through spiky cholla and spindly ocotillo plants leafy from recent rains.
Students work out of the Arivaca Action Center, about 10 miles from the border, and get anthropology credits for five weeks of intense research studying a wide range of issues, from how long the shoes migrants use last to how fast a human body decomposes out in the desert.
Jordan Davis, a 22-year-old history and archaeology student at Calvin College in Michigan, is interested in religious artifacts.
"Outside of water bottles and backpacks, the mental process migrants go through is very important," he says, wiping sweat from his forehead when the group stops to take a break east of Arivaca Lake.
"Just hiking it is physically challenging," he says. "If the willpower is not there, you are not going to make it."
Shrine sites found
When the group reaches a shrine site where rosaries hang from tree branches and dozens of votive candles sit on top of rocks and on the ground, Davis starts snapping pictures.
"Oh my gosh, oh my gosh!" he says when Gokee shows him a shrine to Santa Muerte. The skeleton saint sometimes is linked to the illicit drug trade but recently has found a diverse and growing following north and south of the border. This is the first one Davis has seen during these five weeks in the Arizona desert.
The group records the number of rosaries, candles and prayer cards. They note the GPS coordinates and take photographs of the entire site.
De León, who started his career excavating ancient sites in rural Mexico, knows it may be hard for some people to think of debris as historical artifacts. But it is, he says.
Archaeologists usually study ancient trash. In this case the methods are the same, but it just so happens the trash was left a few years ago - maybe even a few hours ago, he says.
And not everything was left intentionally, he says. He has found pictures of children, love letters and Bibles. Sometimes migrants abandon possessions as they tire and their packs start to feel too heavy or if the smuggler orders them to drop everything before their ride picks them up, he says.
Book to be published
Melissa Hayes, border project manager for the Arizona Department of Environmental Quality, says De León's approach is interesting, but the agency looks at trash from an environmental standpoint.
The debris can block waterways, especially in monsoon season, attract cattle and wildlife and provide fuel to wildfires, she said. Each border crosser leaves about 6 to 8 pounds of trash in the desert, the Arizona Border Trash Project website reports.
De León says it's not always easy to convince people of the value of the project, but as the work gets published, as chapters of books or presentations are made in symposiums, people are coming around.
For Jill Farrell, an Arivaca resident and board member of the Arivaca Action Center, it's good to have young people see with their own eyes what's happening at the border - regardless of the politics.
"It's looking at something through a different lens," she says.
When you think of archaeology, the iconic image is a site, like the pyramids in Egypt, researchers with wood boxes and ladders. That's all true, but it's only part of the picture, says Ben Thomas, an archaeologist and director of programs for the Archaeological Institute of America.
Archaeology is about studying human behavior through the objects people made, used and discarded, he says.
The practice of archaeology of the contemporary is a small branch of the field, he says. But it's an important one.
De León will return to Arizona next year to work on a book about his work, to be published in 2015.
But after that, he is not sure what's next.
With the decline in migration through the Arizona desert and nearly five years of research, he might go to south Texas or Mexico next - either way, he'll continue to study Latino issues.
On StarNet: Find extensive coverage of immigration issues at azstarnet.com/border
"Outside of water bottles and backpacks, the mental process migrants go through is very important. Just hiking it is physically challenging. If the willpower is not there, you are not going to make it."
a 22-year-old history and archaeology student at Calvin College in Michigan
Contact reporter Perla Trevizo at email@example.com or at 573-4213. On Twitter: @Perla_Trevizo