Have Any Animals Evolved to Adapt to Human Activity?

You’ve got questions. We’ve got experts

moth illustration
Have any modern animals adapted to human activity through natural selection? 
  Illustration by Hokyoung Kim

Q: Have any modern animals adapted to human activity through natural selection? Mike Anglin | Dallas, Texas

Human-caused factors have led to anatomical changes in both vertebrates and invertebrates. One example is the peppered moth: In the early 20th century, air pollution killed the lichens they camouflaged on, exposing dark tree bark. The typical light form of the moth started getting preyed upon at a higher rate than its darker counterparts, resulting in a darker species. Similar cases can be found in more than 70 species of moth and butterfly. As pollution levels declined due to regulation, the melanism in these creatures reversed. —Floyd Shockley, entomologist, National Museum of Natural History

Q: How did engineers in antiquity do elaborate calculations using Roman numerals? John Davison | Langhorne, Pennsylvania

It’s difficult to know how much ancient engineers relied on intuition and geometry. Our knowledge of how the Romans used architectural drawings—let alone the mathematics they used to produce them—is also quite limited. We do know that from ancient Roman times through the Middle Ages, Europeans made calculations using the abacus and the counting board; the former used beads, while the latter involved stones or discs called counters. The widespread adoption of Arabic numerals in the 1400s opened the way for more complex forms of mathematics, including algebra—a word that comes from the Arabic al-jabr, the reunion of broken parts. —Peggy Kidwell, curator of medicine and science, National Museum of American History

Q: When fish swim down to deeper levels of the ocean and back up again, does it affect the pressure in their bodies the way altitude shifts or deep-sea diving affects humans’ bodies? Steven Clark | Arlington, Texas

Changes in depth do not generally affect fish the same way pressure changes in altitude affect people, because fish lack lungs. However, most fish do have an enclosed air sac called a swim bladder. They can move air in and out of that sac to help them with buoyancy. But this is a slow process, and if a fish comes up too rapidly (for example, if it’s caught on a fishing hook in deep water and then is quickly reeled to the surface), the pressure change can be fatal, because the swim bladder can’t be deflated fast enough. —Carole Baldwin, chair of vertebrate zoology, National Museum of Natural History

Q: Why do many states have such odd shapes, with wavy natural borders on some sides and straight lines on others? Raymond Lopez | Newtown Square, Pennsylvania

The borders of the original 13 colonies were based on land grants from the British crown, though it took some debate to settle their final boundaries. Natural features played a role in state shapes across the nation, as did railroads and canals. Straight boundaries west of the Appalachians were defined by the public land survey, using latitude and longitude. Due to limitations in surveying methods, many of those lines weren’t perfectly straight and needed corrections along the way. Slavery also influenced many state borders. Internationally, U.S. borders were established by treaties with the U.K./Canada and Mexico. —Daniel G. Cole, chief cartographer, Smithsonian Institution

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This article is a selection from the April/May 2023 issue of Smithsonian magazine

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