There are places, like the medical examiners office in Tucson, Arizona, where the human cost of migration to the United States is counted.
Dr Bruce Parks, the chief medical examiner, is a tall, thin, quiet man. He put on rubber gloves and led me over to a zippered plastic bag sitting on a steel gurney.
"These people, we don’t know who they are, and we may never know," he says, opening the container.
Dr Parks gently withdraws a skull, grey and dry, weathered by the sun and gnawed by scavengers. What's in this bag was once a man. He was found in the desert outside Tucson, along the route that migrants take from Mexico.
"I don't know his age," Dr Parks says, turning the skull slowly in his hands. "He had teeth once, but the teeth are not there anymore - evidently they have fallen out due to animal activity."
'Awful and lonely'
Dr Parks has been working long hours this month, as more and more men and women from Latin America have been found in the nearby desert, along the trails to "El Norte" - the United States.
"This year, or this particular month of the year, has been one of the worst months ever," he says wearily. "To date we have had 53 bodies made known to us and brought to this office."
The people who wind up in Dr Parks' morgue died awful and lonely deaths - suffering from thirst and heat. He's found evidence some committed suicide rather than endure that pain - corpses with their veins opened by razor blades, and a man who hung himself with his own shoelaces.
Its difficult to imagine what horror and hopelessness they felt in those last moments, alone in the wasteland, far from home, their hopes for a new and better life cruelly mocked by the relentless desert heat.
No one is certain why so many are dying just now. Some believe it is because the US government has stepped up more intensive patrols and built stronger barriers at traditional border crossing spots. As a consequence, determined migrants now must trek through the most desolate and deadly terrain along the border.
It's a grueling trip over rutted dirt roads into the heart of the desert. We travelled in an air conditioned four-wheel-drive Chevy Tahoe SUV. Migrants make the trip on foot. Most carry just a plastic jug of water—not nearly enough for a journey of five to seven days across sun-blasted, rocky wastes bristling with cactus and thorny scrub.
On the day we went into the desert, the temperature hovered around 37 degrees C. Water is what people need most there to survive. And some take it upon themselves to bring water into the wilderness.
At a series of stations along the migrant route, marked by blue flags, there are casks of water maintained by a group called Humane Borders.
Bob Cabigas, a volunteer with the group, has filled the barrels full every week for over three years. Examining one container with a water-volume measuring device, he can tell someone has come by to drink. "This one needs some water," he says. "There's about 15 gallons somebody used."
At each stop, Cabigas cups his hands around his mouth and shouts into the desert. "Do you need help?" he yells, in Spanish. "We have water. We have food." Sometimes, he says, migrants emerge from the brush and drink. Sometimes, he finds their bodies, rotting.
"It's the worst place in the world to be walking," Cabigas says. "Its just brutal, a very brutal place."
Not all of that brutality is from nature - some is man-made. Volunteers say that in recent months many of the barrels have been vandalised, and the potentially life saving water has been simply spilled out on the desert floor.
The increased vandalism appears to have coincided with the rising intensity of the debate over illegal immigration, sparked by Arizona's stringent immigration law.
"They took the barrel and then they stabbed it like this," Cabigas says, miming frenzied knife blows on a barrel. "You can see the hate. Then they shot it, then they tore the flag down."
It's possible the sabotage might have something to do with the sharp increase in migrant deaths. But we will probably never know ... because the desert keeps its secrets.