Every dander, hair follicle, eyelash and drop of saliva poured out of your body contains instructions written in a chemical code that is unique to you.
According to a new study, technology has advanced to the point where it is now possible to sift bits of human DNA from the air, water or soil and decipher personal details about the individuals who dropped them.
As helpful as this may seem, the study’s authors warn that society may not be prepared for the consequences.
“Anytime we make a technological advancement, there are useful things that the technology can be used for and in terms of things the technology can be used for,” say University of Florida zoologist David Duffy, who led a project testing the limits of sequencing human DNA from the environment.
“These are issues that we try to address early, so that policymakers and society have time to develop regulations.”
The Earth’s surface is littered with discarded plant and animal cells and disintegrated microbes, releasing what researchers call environmental or “e” DNA.
By amplifying the tiniest bits of eDNA and reading the sequences, researchers can accurately create an ecological cast list of organisms present in a habitat, all at speeds and costs not achievable with fieldwork.
In addition, those representative genetic samples can also yield insights that no other process could achieve on its own, such as informing researchers about the presence of diseases or the relationships between populations.
This is all well and good when zoologists pluck long-lost genes from ancient sediment, or fish for signs of a mythological monster in Loch Ness. But in that genetic soup there will undoubtedly also be pieces of material left behind by people passing by. And unlike Nessie, people tend to get a little funny about who sniffs their genetic secrets.
While older methods of sequencing have struggled to find meaningful human genetic sequences in eDNA samples, a process known as shotgun sequence is not so limited, as demonstrated by Duffy and his team in their recent study.
The research team took water and sand samples from near the Whitney Laboratory for Marine Bioscience and Sea Turtle Hospital at the University of Florida, and from riverside environments in Duffy’s home country of Ireland. Among the locations where they collected samples was an isolated island and mountain stream far from human habitation.
Referred to as human genetic bycatch (HGB), many of the chromosomal fragments they identified using the shotgun approach contained identifying information about their source.
Only the island and the remote stream were free of human DNA, although traces of the research team’s own genes could be extracted from their footprints in the island’s isolated sands.
Air samples from the University’s Sea Turtle Hospital also contained eDNA traceable to staff, animals and common animal viruses.
“We’ve been constantly surprised throughout this project at how much human DNA we’re finding and the quality of that DNA,” say Duffy. “In most cases, the quality is close to that of a human sample.”
It is easy to envision ways in which such highly detailed genetic assays using HGB could be applied to the field of epidemiology or population genetics. Still, the sources of the identifiable DNA in this experiment all agreed to be involved in the study, consistent with the ethics of published genetic research.
“It’s standard practice in science to make these sequences publicly available. But that also means that if you don’t rule out human information, anyone can come along and collect this information,” say Duffy.
“That raises questions about consent. Do you need permission to take those samples? Or do you set controls to remove human information?”
As a forensic tool, its benefits are something of a double-edged sword, expanding methods to trace individuals to a crime scene.
But in light of the CSI effect, where DNA test results are easily misinterpreted by a Hollywood-influenced judiciary, the legal ramifications of HGB identification have also yet to be fully explored.
There is also concern about how far public scrutiny should extend in the name of security.
“To be sure, solving crime is a good thing,” say Natalie Ram, a University of Maryland lawyer who was not involved in the investigation.
“But exploiting involuntarily gathered genetic information for research purposes carries the risk of putting us all under constant genetic surveillance.”
We can imagine an authority keeping an archive of DNA fragments that made it to just about every crime scene that a few of us would feel comfortable being a part of.
It is far from the first time that society has struggled with the ethical and legal issues of genetic rights, Naturally. But the Internet collecting personal genetic information is clearly growing, prompting us to keep asking who should have the final say on the unique code that describes us as individuals.
This research was published in Natural ecology and evolution.