Is the nail-biting habit the result of nature, nurture or something else? Some scientists trying to understand where behavioral as well as physical traits come from have turned to the study of identical twins, particularly those who were separated at birth. In this article — illustrated with a series of compelling photos — Peter Miller describes the Minnesota Study of Twins Reared Apart, in which psychologist Thomas Brouchard and colleagues examined 137 sets of twins over two decades. Their results are filled with surprising anecdotes and tales of twins who grew up in different homes but exhibit spooky similarities, which range beyond looks and height and weight to career choices and even preferred cigarette brands.
But it’s when identical twins turn out different that things really get interesting. Miller writes about a pair who both suffer from autism, but one with more severe symptoms than the other. Both are participating in a study at Johns Hopkins University on epigenetic processes, the chemical reactions that seem to strengthen or weaken the expression of specific genes. These differing reactions are why identical twins who share environmental circumstances as well as DNA can still turn out different. “If you think of our DNA as an immense piano keyboard and our genes as keys . . . then epigenetic processes determine when and how each key can be struck, changing the tune being played,” explains Miller.
This has to rank among the more tedious tasks given to grad students: To distinguish among ants used in experiments, researchers use a brush to paint color codes on their itty-bitty backs. For the benefit of budding entomologists and, really, anybody else who wants to go all Georges Seurat on a bunch of bugs, scientists at Arizona State University’s Pratt Laboratory have assembled a handy how-to video, which they recently posted on YouTube. The instructions are practical: How do you keep them from wriggling? Knock them out with carbon dioxide. How do you hold them in place? Bind them to a sponge with a single strand of human hair. How much paint do you need? Not much. (Duh.) It’s all done in the name of science, naturally, but you can picture a sort of ant-farm art installation, a wriggling mosaic of colored dots.