This technique of ancient soil DNA extraction seems quite a game changer. I wonder if it has to be a cave environment / permafrost or simply any layer of undisturbed soil / sediment. Imagine if you can go around the planet collecting soil cores creating a completely new window into prehistory...

[1] https://arstechnica.com/science/2017/04/no-bones-needed-anci...

[2] https://www.popularmechanics.com/science/archaeology/a361770...

[3] https://scitechdaily.com/extracting-ancient-dna-of-long-exti...