Sorting things into categories is one of the first scientific skills that children can learn. Categorizing, be it socks, rocks or plants, just seems to be an innate human urge. Categories help organize the world around us. Naming those categories allows us a simpler way to identify, compare and talk about them. Classification systems are essential to science; they act as the scaffolding that enables scientists to stand up close and get to know plants, rocks or anything else.
But any classification system, however useful, is ultimately simplistic. No such system perfectly describes reality and the wonderfully messy wonders of nature. And so classification systems get tweaked, revised, renovated or completely replaced to accommodate new discoveries. And, as we have reported before (“The name of the fungus,” SN: 5/3/14, p. 22), and will again (Susan Milius is now at work on a story about the latest thinking on biological classification), scientists spend a good deal of time and energy arguing about such changes.
In this issue, two feature stories describe the questioning of existing classification schemes and proposals for new ones. In “Solo planets may be surprisingly common,” Ashley Yeager focuses on how the discovery of rogue planets — those that don’t orbit a star — is challenging the definition of a planet. So far, researchers have found dozens of untethered worlds, and some scientists suggest that there may be billions more. As astronomer Michael Liu says, the galaxy’s contents are turning out to be much more complicated than current definitions allow.
Bruce Bower explores a very different way of knowing and naming in “Telling stories from stone tools.” The system for categorizing tools used by human ancestors has outlived its usefulness, critics say. It may actually be impeding understanding of the development and evolution of ancient stone tools. Alternate schemes are proliferating, some involving the possible techniques used to make spearpoints, hand axes and other tools. Whatever the scheme, Bower writes, truly elucidating the mind-set of those who made the primitive tools may be out of reach. But developing effective categories is the surest bet for the greatest understanding possible.
As Confucius said, “The beginning of wisdom is to call things by their proper name.