Welcome to Quantum Magazine's podcast. Each episode we bring you stories about developments in science and mathematics. I'm Susan Vallett. A remote cave in western Georgia, east of the Black Sea Shore, is a treasure trove for scientists seeking answers among the scattered

stalagmites. But this team of archaeologists is only mildly interested in the ancient bones

on the floor of the cave. Instead, they gather buckets of sediment on the hunt for ancient DNA,

like that extracted from the mummified remains of copper-aged

humans and frozen mammoths. This kind of DNA used to be a precious find, obtained

only through the careful sequencing of well-preserved fossils and bones. It took luck, money,

and usually attract to the Arctic. But now, scientists are

finding it everywhere.

The scientists published the results of their Georgian cave study last spring in the journal Scientific Reports.

Their work shows that bears, roe deer, and bats were present in this region at least as far back as

80,000 years ago.

But finding traces of late Pleistocene animals just scratches the surface of what can be done

with environmental DNA or e-DNA.

These are traces of genetic molecules from long-dead organisms that survive as cell-free

residues in the soil or other terrain.

One of E-DNA's advantages is that it can signal the remnants of organisms with soft bodies,

allowing scientists to reconstruct entire ecosystems,

complete with plants, algae, and more. Environmental genomics, also known as metagenomics,

truly lets us see the ancient world in a few grains of sand. Laura Parducci is an evolutionary

plant ecologist at Uppsala University in

Sweden who wasn't involved with the paper.

The big benefit is that you can get DNA from species that are actually not visible

...