“Anthropogenic” is a key word of our time. It means caused by, and/or originating with, humans. It’s generally used to refer to climate change. But anthropogenic warming isn’t the only thing we’re collectively causing here on earth. Humans have become a major evolutionary force. In fact, we may be the most powerful evolutionary force going. We are driving rapid evolution—contemporary evolutionary change—in other species at rates that seem to be faster than anything else in history, barring the five great mass extinctions of earth history.
In their introduction to a special issue of Philosophical Transactions: Biological Sciences on human influences on evolution and the ecological and societal consequences thereof, Andrew P. Hendry, Kiyoko M. Gotanda, and Erik I. Svensson list some of the anthropogenic factors influencing evolution today, which include
[p]ollution, eutrophication, urbanization, habitat fragmentation, climate change, domestication/agriculture, hunting/harvesting (including fishing), invasion/extinction, medicine and emerging/disappearing diseases.
It’s a lot. And, of course, these factors aren’t necessarily separate and distinct. Consider fish, for instance, beset by hotter, more acid waters; many different kinds of pollution; and eutrophication, among other things.
Antibiotic resistance is the best known of our evolutionary forcings. With too-liberal use of antibiotics in both human and domestic animal populations, we’ve channeled pathogens into evolving super-resistance against antibiotics.
There any many other examples. The peppered moth is a now classic one, but it’s only the most famous of more than 100 other species of moth affected by industrial melanism. Formerly rare dark (melanic) versions of peppered moths began to predominate as the Industrial Revolution coated England’s Midlands with dark industrial filth. The dark ones blended in, so they were less likely to be picked off by predators and more likely to pass on their genes. Once the air got cleaner, the lighter ones returned to their former prominence.
Killifish are another example. These small fish are now able to survive in polluted environments that would normally kill most species. Populations in places like Newark Bay have evolved enormous resistant to industrial pollutants.
Rapid evolution has also been seen and studied in such animals as wolves (Chernobyl Exclusion Zone), Crested Anoles (Puerto Rico), Fairy-wrens (Australia), Spotted Hyenas (Tanzania), Red Deer (Scotland), and Red Squirrels (Canada). Fish have gotten smaller because we’ve removed the large ones out of the gene pool and smaller ones get through nets easier. Female elephants are losing their tusks in response to slaughter by ivory poachers.
Hendry et al. draw distinctions between “how humans interact with their ‘enemies’ (or ‘adversaries’) versus their ‘friends.’” Enemies are things like “weeds, pests, and pathogens” which we want to decrease. Efforts to do so can favor resistance/tolerance to our control efforts. Friends are things like crops, natural resources, and biodiversity, which we strive to increase. Here we can facilitate adaptive evolution that benefits the target species. In the case of both enemies and friends, there can be “spillover to influence non-target species.”
The authors also write that some species may be “frenemies,” that is, good or bad at different times and places. Meanwhile, many species (“neighbors”) are just there, living besides us, neither “good” nor “bad” for us, but just just as likely to be driven to evolve because of the multi-pronged pressures we put on them, often quite unintentionally.
Without even realizing it, we’ve actually become pretty god-like in our powers. We’re controlling what lives and dies; what evolves and what becomes extinct. Our domesticated species dominate the biosphere: 34.4 billion chickens, 1 billion cattle, 784 million pigs. Our stuff—roads, buildings, phones, daily coffee cups—may now outweigh all the life on earth.
Welcome to Anthropogenic Earth.
“From our increasing knowledge of how humans influence evolution comes the opportunity, perhaps even the responsibility, for humans to do something about it,” conclude Hendry, Gotanda, and Svensson, noting numerous ways we already do so. “The future affords even greater opportunities to influence evolution in informed, effective, restrained and safe directions.”