Survival of the Weakest
Humans Affecting Evolution of Other Species
Lay scientists tend to think of evolution as a glacially slow process, with changes measured in hundreds of thousands of years, not decades. However, growing collaboration between ecologists and evolutionary biologists is highlighting a phenomenon called “contemporary evolution” — and it ain’t pretty. Turns out, by culling the largest, healthiest, and most robust specimens from a species, human beings can precipitate a sort of rapid devolution, an evolutionary trend toward smaller, weaker populations that works over generations, not centuries. The phenomenon can be observed across the animal world — for example, hunters have left mountain sheep in Alberta, Canada, shrinking, along with their horns — but it is particularly perspicuous in the world’s fisheries. Some scientists trace the precipitous decline of the cod population to fishing practices that value the largest fish; the result has been a population of fish that mature earlier and smaller, are unable to produce robust offspring, and lack the genetic diversity to breed their way out of trouble. Researchers recommend a broad rethinking of practices for protecting endangered species and managing wildlife habitats, fisheries, and hunting ranges.