HUNTSVILLE — In the shadows of pine trees, a woman in a white overalls leans over the dead body of a fat, naked man. She brushes his cheek with a cotton swab, as eight scientists look on. "Can you apply a bit more pressure, to get some DNA?" one scientist asks. Adds another, "but not too much, don't harm the skin."

It's been a week since the body was placed here. Two tattoos and a scar are reminiscent of the life he must have lived. But the scientists don't care about the past. They're interested in what happens to the body after death, when bacteria, protozoans and fungus will entirely decompose the body over the next couple of weeks. They eat through the skin that once felt, the heart that once beat, the nerve cells that recorded all kinds of memories. For nature, the corpse is a source of nutrients — nitrogen, potassium, sulfate and other elements, dissipated bit by bit. Dust to dust.

Geneticist Jessica Metcalf wants to understand exactly what happens during this process. This may help to determine more precisely the time of death in some murder investigations. That's why she's come to the Southeast Texas Applied Forensic Science Facility (STAFS) in Huntsville, Texas, with her colleagues this morning. In these woods, donated corpses decompose in the name of science. Americans call places like these "body farms." Behind a big fence, there are no flowers. Only death is blooming: red and orange gashes, green and yellowish rotting skin. Bones sit next to a white skull. An old man lies in a plastic tub, his grey hair floating in the water.

"I never would have thought about ending up here," Metcalf says. As a student, she considered going to medical school. "But I was even incapable of dissecting a worm, or a frog." So instead she pursued for gene technology. Her doctoral thesis was about the genetic material of extinct animals, which means she also studied fossilized animal excretions. She later became interested in human microbiota, the community of viruses, bacteria and protozoans that live in our intestines and skin. One of the main questions for researchers is how microbiota have changed over the course of human evolution.

Researchers at Texas State's Forensic Anthropology Center — Source: Official website

That's how Metcalf also began studying decomposition. In her laboratory, she studied 40 dead mice, analyzing their bodies, taking samples and isolating their genetic material. That's how she got a snapshot of the microbiota that live in corpses. Metcalf found a pattern: Different mice she analyzed the same day had the same communities of microbiota. Different days, different microbiota.

And that could represent a significant breakthrough. The always identical succession of microscopic scavengers seem to obey a sort of microbes clock that starts to tick at the very moment of death. Even today it's difficult to determine the exact times of death, a task that is critical for murder investigations. That's why Metcalf and her colleagues have moved on to human corpses. A first study seems to confirm the information obtained via mice.

"During the first 25 days, we are able to determine the time of death with a preciseness of plus or minus two to four days," Metcalf says. Now they are researching how the weather and nature influence body decomposition.

Research methodology

The research team wants to scatter 36 corpses over the next 12 months, three per season at three different locations in the United States. There are so many questions: Where and how should samples be taken? How fresh do the corpses need to be? Should they have been cooled first, or even frozen? Should they be placed on their stomachs or backs? Each detail could be important for study. Over recent years, dubious forensic methods have repeatedly been applied in court, leading to innocent people going to prison because of flawed statements from experts.

STAFS logo — Source: Facebook page

The first body farm opened in the southern U.S. state of Tennessee in 1981, and others soon followed. Today there are six such American farms, and one in Australia is about to open.

Life after death

Sibyl Bucheli studies insects, especially those living in corpses. When visiting the body farm, she wears dark clothes and boots. "Team Player" is written on her cap in pink glitter lettering. Sitting next to a corpse, she points to the small orange mites crawling over the body.

This particular corpse was placed here in November. The wizened skin has a yellowish-brown color, and it's difficult to tell whether the body was a man or a woman because there's a hug hole where the genitals once were. "Vultures prefer genitals and eyes," Bucheli says. The arms are spread away from the body, which happens when they inflate. A scientist calls it the "death dance."

Bucheli is interested in the microbes on the corpse. The DNA she obtains is similar to the what was collected from Metcalf's mice. When someone dies, it's not the end — at least not for the billions of microbes that a body carries on and inside it. Because the immune system has ceased fighting them, they proliferate. The bacteria produces gas, which inflates the body until it explodes. The oxygen entering the body then allows other bacteria to survive. Eventually nematodes, or minuscule worms, feed on the corpse's bacteria. The process seems exceptionally well organized. "And it's particularly efficient," Metcalf says.

There is most likely an ongoing war among the different microbes on this body, similar to the fight for resources of lions, hyenas and vultures. And this competition has led to efficient recycling over millions of years. The microbe's weapons can be interesting for humans too, and the research could lead to finding "a new type of antibiotics," she says.

The experience of working with dead bodies is indescribable, and something to which researchers never entirely grow accustomed. Looking at a dead body still shocks, but the scientists see it pragmatically.

Finally, they discuss what should happen with the bones. Even dry bones end up being consumed by microbes. Metcalf hopes there's some kind of a clock too because it could help to narrow down the moment of death, even if there's nothing left but the skeleton. They agree to take samples once a week.

Eventually, the work's done. After all this death, it's back to life. Time for lunch. "There's a great grill close by," one of the scientists says.

"Seriously?" Metcalf asks, shaking her head. "Ribs?"