Shreds of Evidence: The Rise of eDNA

A bee alights on a flower. A bullfrog slips into a pond. In a leafy park, a weary pedestrian shuffles toward home.

Each fleeting moment leaves behind a wealth of genetic information — the bee’s foot on the flower petal, the frog’s body touching the water, the feverish pedestrian’s breath suspended in the air. And scientists are increasingly able to collect this genetic information to conduct a range of investigations, to see who or what was in a space even after they’ve gone.

Aptly called environmental DNA, or eDNA, the approach involves hoovering up all the genetic bits left behind by skin, hair, spit, and more, and it is cropping up in fields including biology, ecology, and forensics.

The possibilities are far-ranging: Scientists are using eDNA to identify specific species of animals or microbes in an ecosystem that may have otherwise remained undetected. And they are also using the tool to cast a wider net, by analyzing all of the genetic material in a particular scoop of water or mud or puff of air, which can function as a sort of large-scale genetic census.

But how exactly does eDNA work, and how does it differ from older sampling techniques? Who’s using eDNA and why? And, crucially, what are its key promises and perils? If eDNA can be used to locate an animal, what happens when it can locate humans? Should we be worried about privacy?

In a six-part series, Undark explores the origins of eDNA collection, its use by pathogen hunters, conservation biologists, entomologists, and even scientists hoping to use eDNA to locate soldiers missing in action — as well as its commercial allure. Emerging markets for eDNA analysis are poised to transform everything from environmental monitoring to understanding the terroir of honey. And with new applications on the horizon, the eDNA era is raising keen hopes (and some nagging worries) about a technology that might soon make every living thing visible, even when it’s no longer there.