Traces of humans in nature leave genetic treasures

David Duffy, a wildlife geneticist at the University of Florida, just wanted to develop a better way to monitor sea turtle diseases…but he found human DNA everywhere.

environmental nucleic acid

Over the past decade, wildlife scientists have developed techniques to elevate environmental DNA, or eDNA, which is tiny amounts of genetic material that living creatures leave behind. Environmentalists consider this powerful and inexpensive tool to be found everywhere in the air, water, snow, honey, and even a cup of tea.

Researchers use this method to monitor invasive species before they take hold, to track populations of vulnerable or predatory wildlife, and even to rediscover species thought to be extinct. Environmental DNA technology is also being used in wastewater monitoring systems to detect viruses such as COVID-19.

Scientists using environmental DNA throughout their work have found amounts of human DNA that they consider to be a form of contamination, or some kind of accidental presence of human genes tainting their data.

human trace

Now, what would happen if someone deliberately collected environmental DNA from humans?

Erin Murphy, a law professor at New York University School of Law who specializes in the use of new technologies in criminal law, notes that law enforcement officials are drawn to the new DNA collection techniques, as police agencies are quick to take advantage of unproven tools, such as using DNA to put Possible charges for suspects.

This leads to dilemmas on the level of privacy and civil liberties, especially since technical developments are now making available masses of information from smaller and smaller samples of environmental DNA. Duffy and his colleagues used an available and inexpensive technique to see how much information they could glean from human DNA collected from environmental conditions as diverse as outdoor waterways and the air inside a building.

Their findings, published May 15 in the journal Nature Ecology and Evolution, show that scientists can derive medical and ancestry information from fragments of human DNA circulating in the surrounding environment.

Criminal ethicists and legal scholars say the University of Florida team’s findings highlight the need for comprehensive genetic privacy laws. These findings also highlight the unbalanced regulation of these technologies in the United States—which makes it easier for law enforcement officials to employ immature technologies; This is in contrast to the difficulties that researchers face in obtaining licenses for studies required to prove the effectiveness of a specific new system.

Trash or genetic treasures?

It’s been clear for decades that fragments of our DNA are everywhere, but in the past it didn’t seem that important. Scientists believed that the DNA circulating in the surrounding environment was fragmented and too small to have an effect on lifting it, and too weak to be used to identify a person unless it came from well-defined samples such as a blood stain or an object someone touched.

But wildlife researchers took interest in environmental DNA because they were originally looking for tiny bits of DNA to scan what they call a “barcode” (digital linear code) that identifies the species to which creatures belong using a sample. But after finding “surprising” levels of human DNA in their samples while monitoring a disease afflicting sea turtles in Florida, Duffy and his colleagues set out to build a more accurate picture of the state of human DNA in the surrounding environment, and to see how much information it might reveal about people in the area. .

To prove that their technique worked in one of their experiments, the team raised a mug-sized water sample from a creek in St. Augustine, Florida, and then inserted the genetic material they removed into a device that allows researchers to read strands longer than DNA. The $1,000 device they used is about the size of a cigarette lighter and plugs into a laptop like a flash drive.

The team raised from the samples a clearer and more accurate human DNA than they expected at a time when the expansion of knowledge in the field of human genes ensures the discovery of a huge amount of information from the analysis of limited samples.

The researchers raised enough mtDNA – passed directly from mother to child over thousands of generations – to paint a picture of the genetic ancestry of a group of people living around the stream that barely matches the racial composition reported in the most recent census of the area (although Researchers consider ethnic identity to be a weak factor in genetic ancestry. The researchers found that one mitochondrial sample was sufficient to meet the requirements of the Federal Missing Persons Database. They also found prominent mutations that carry a high risk of diabetes, heart problems, and several eye diseases.

Forensic analysis

Anna Lewis, a researcher at Harvard University who specializes in the ethical, legal, and social implications of genetic research, said that environmental DNA has not been discussed extensively among bioethicists. But this discussion will inevitably follow the results of Duffy and colleagues’ research.

Lewis added that the technology, which is based on environmental DNA, could be used to track certain types of people – for example, people who come from certain lineages or who suffer from specific diseases or disabilities.

The researchers agree that the consequences of these uses depend on who uses the technology and why. While environmental DNA samples from the ocean may help public health researchers determine the incidence of a disease-causing mutation, the same sample may contribute to the location and persecution of ethnic minorities.

Lewis believes, “This matter gives the authorities a new powerful tool. Globally, there are many reasons to feel anxious, ”noting that countries such as China have begun to conduct broad and explicit genetic prosecutions of minorities, and that tools such as environmental DNA analysis facilitate these pursuits.

Research into human environmental DNA may also become an ethical minefield. However, this depends on the extent to which these researches are able to determine the identity of the individual, which has become possible in some cases.

Robert O’Brien, a forensic biologist at Florida International University and a former forensic DNA analyst, has revealed that the kind of genetic data that Duffy and his colleagues have lifted from public places is ineffective in the means that law enforcement currently uses in the United States to identify individuals.

O’Brien explained that when law enforcement DNA analysts compare a sample from a crime scene to a suspect’s, they look at 20 different markers in the human genome that are checked against the FBI’s Combined DNA Indexing Program (CODIS) system. However, these signs only work if it is confirmed that a number of them descended from the same person. But the fragments of environmental DNA Duffy studied could only detect one marker at a time.

In contrast, forensic researchers suggest that the identification of individuals using environmental DNA is now possible in enclosed spaces with a small number of people. Last October, a research team from the Forensic Research Center of Oslo University Hospital tested a new technique for lifting human DNA from air samples, and succeeded in building complete genetic DNA files from DNA that traveled through the air in an office.

The New York Times Service.