2023-05-15 20:00:35
On the beach, in the ocean and rivers, but also in the air, from one end of the world to the other. Human DNA is everywhere. We cough, spit, leak and ‘dump’ our DNA in all of these places and countless others: signs of human life can be found practically everywhere, according to a study by the University of Florida, published today in ‘Nature Ecology and Evolution’ , apart from the islands and the most remote mountain peaks.
“During this project, we were really surprised by the amount of human DNA we found and the quality of that DNA,” comments David Duffy, a professor at the University of Florida and project leader. “In most cases, the quality is nearly equivalent to that of a sample taken from a person.”
Duffy’s team used environmental DNA (eDNA) to study endangered sea turtles and the viral cancers that frequently affect them. Scientists knew that human eDNA would end up in their turtle samples and probably many other places. They wondered how much human DNA they would find and whether it was intact enough to contain any useful information. The answer baffled them. In fact, they found quality human DNA in the ocean and rivers surrounding their laboratory, both near the city and away from human settlements, as well as in the sand of isolated beaches. At this point they repeated the test on a remote island never visited by people: as expected, it was devoid of human DNA, but the researchers managed to recover the DNA from the footprints left in the sand of the test participants and were also able to sequence – with their consent – parts of their genomes.
Duffy also tested the technique in his homeland of Ireland. And, following the path of the river that meanders through his city to the ocean, he has found human DNA everywhere except in the remote mountain stream where the river originates, far from civilization.
This ubiquity of our DNA is both a scientific advantage and an ethical dilemma, say the researchers who sequenced this widespread DNA in the environment, since it is not a question of faint traces. For example, benefits could include tracing cancer-specific mutations from wastewater analysis, pinpointing unknown archaeological sites, or even identifying suspects from DNA floating in the air at a crime scene. But, the researchers underline, this type of genetic information, which is so personal, must be managed with extreme care, no longer contained in a blood or saliva sample but simply in a handful of sand or in a vial full of water.
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