There is now a fish that has evolved immunity to PCB’s. PCB is a substance designed to use as an insulator in high-heat electrical equipment (like the transformers used in the electrical grid, or household radios and such). It is very bad for the environment, was taken out of use years ago, but the thing is, because it was designed to stand up to very tough conditions, it does not break down naturally. I grew up not far from where most of them seem to have been made, and was actually involved in some of the cleanup.
So, today, it is interesting to read about this fish:
Bottom-feeding fish in the Hudson River have developed a gene that renders them immune to the toxic effects of PCBs, researchers say.
A genetic variant allows the fish to live in waters notoriously polluted by the now-banned industrial chemicals, and distinguishes the fish–Atlantic tomcod (Microgadus tomcod)–as one of the world’s fastest evolving populations.
“This is very, very rapid evolutionary change,” said Isaac Wirgin, an environmental toxicologist at New York University’s School of Medicine, and the study’s lead investigator. “Normally you think of evolution occurring in thousands to millions of years. You’re talking about all this occurring in 20 to 50 generations maybe.”
… and compare it to this, which did not end well.