The Best American Science and Nature Writing 2014 by Deborah Blum

are active, sending out chemical messages that affect the activity of the cell. This variable gene activity, called gene expression, is how your body does most of its work.
    Sometimes these turns of the dimmer switch correspond to basic biological events, as when you develop tissues in the womb, enter puberty, or stop growing. At other times gene activity cranks up or spins down in response to changes in your environment. Thus certain genes switch on to fight infection or heal your wounds—or, running amok, give you cancer or burn your brain with fever. Changes in gene expression can make you thin, fat, or strikingly different from your supposedly identical twin. When it comes down to it, really, genes don’t make you who you are. Gene expression does. And gene expression varies depending on the life you live.
    Every biologist accepts this. That was the safe, reasonable part of Robinson’s notion. Where he went out on a limb was in questioning the conventional wisdom that environment usually causes fairly
limited
changes in gene expression. It might sharply alter the activity of some genes, as happens in cancer or digestion. But in all but a few special cases, the thinking went, environment generally brightens or dims the activity of only a few genes at a time.
    Robinson, however, suspected that environment could spin the dials on “big sectors of genes, right across the genome”—and that an individual’s social environment might exert a particularly powerful effect. Who you hung out with and how they behaved, in short, could dramatically affect which of your genes spoke up and which stayed quiet—and thus change who you were.
    Robinson was already seeing this in his bees. The winter before, he had asked a new postdoc, Cédric Alaux, to look at the gene-expression patterns of honeybees that had been repeatedly exposed to a pheromone that signals alarm. (Any honeybee that detects a threat emits this pheromone. It happens to smell like bananas. Thus “it’s not a good idea,” says Alaux, “to eat a banana next to a beehive.”)
    To a bee, the pheromone makes a social statement:
Friends, you are in danger.
Robinson had long known that bees react to this cry by undergoing behavioral and neural changes: their brains fire up and they literally fly into action. He also knew that repeated alarms make African bees more and more hostile. When Alaux looked at the gene-expression profiles of the bees exposed again and again to the alarm pheromone, he and Robinson saw why: with repeated alarms, hundreds of genes—genes that previous studies had associated with aggression—grew progressively busier. The rise in gene expression neatly matched the rise in the aggressiveness of the bees’ response to threats.
    Robinson had not expected that. “The pheromone just lit up the gene expression, and it kept leaving it higher.” The reason soon became apparent: some of the genes affected were transcription factors—genes that regulate other genes. This created a cascading gene-expression response, with scores of genes responding.
    This finding inspired Robinson’s kidnapping-and-cross-fostering study. Would moving baby bees to wildly different social environments reshape the curves of their gene-expression responses? Down in Ixtapan, Robinson’s collaborators suited up every five to ten days, opened the hives, found about a dozen foster bees in each one, and sucked them up with a special vacuum. The vacuum shot them into a chamber chilled with liquid nitrogen. The intense cold instantly froze the bees’ every cell, preserving the state of their gene activity at that moment. At the end of six weeks, when the researchers had collected about 250 bees representing every stage of bee life, the team packed up the frozen bees and shipped them to Illinois.
    There Robinson’s staff removed the bees’ sesame-seed-size brains, ground them up, and ran them through a