Scientists have proposed calling this the Anthropocene - the man-made epoch. Now, add evolution to the list of things humans are reworking.
We tend to think of evolution as something that used to happen – a force that shaped our natural world and, then, somehow just stopped. But, of course, evolution hasn’t stopped. New genetic mutations are still popping up, and natural selection is still picking the fittest variants. Same old, same old. Or almost.
In her new book, Unnatural Selection: how we are changing life gene by gene, environmental toxicologist and author Dr. Emily Monosson explains how man-made chemicals - antibiotics, pesticides, and myriad environmental pollutants - may be forcing rapid evolution in new directions. Here are three examples:
- Antibiotic resistance: Methicillin-resistant Staphylococcus aureus (MRSA) is just the tip of the iceberg. Bacteria have been developing resistance to antibiotics since the wonder-drugs were first introduced to the medical market in the 1940's. In the past few decades, resistant strains have been popping up faster than new antibiotics, prompting some experts to worry about a "post-antibiotic" world in which bacterial infections now considered routine, once again become killers. I only wish I were being hyperbolic.
- Pesticide resistance: The pesticide DDT is best known for its widespread, unintended ecological consequences - the subject of Rachel Carson's Silent Spring. Ironically, some of the very pests DDT was intended to wipe out - houseflies, mosquitos, even bedbugs - have developed resistance to the pesticide. And it's not just DDT. A whopping 570 insect species are resistant to at least one insecticide, and some to multiple different ones.
- PCB resistance: Over the past few decades, small fish up and down the Atlantic seaboard have - quickly, and out of sheer necessity - developed the ability to survive incredibly high concentrations of toxic chemicals known as polychlorinated biphenyls (PCBs). That may sound like a good thing, but there are trade-offs. Resistant fish can pass toxins on to susceptible fish, birds, and mammals higher up the food chain. In some cases, they also appear to be less able to survive when placed back into clean water. Go figure.
Monosson says the fact that all of these phenomena are called "resistance" may be symptomatic of a broader, militaristic, us-vs.-them attitude toward the natural world. As we humans have sought to conquer nature, nature has risen up in revolt. Monosson says her research has made her think more about the possibility - benefit, even - of living with what, in the grand scheme of things, could be considered minor inconveniences and saving the big guns for true killers and significant threats.