Microbes frozen in ice for eons are evolving as they thaw.
While they pose little threat to humans now, they could force out existing microbial populations, with unknown effects.
Don't expect to see strange, cobbled-together creatures like miniscule Frankenstein's monsters climbing out onto a shore near you.
The world's ice sheets, scientists now say, are a gigantic reservoir of microbial life – some of which are relics hundreds of thousands of years old. Most of what has melted out and been identified appears related to common soil and marine bacteria. But scientists see evidence that these bugs are evolving within the ice.