When your stomach’s empty, it pumps out the hormone ghrelin, to whet your appetite and get your juices flowing. But ghrelin doesn’t just make you crave a bite. It helps you track it down too—by sharpening your sense of smell. That’s according to a study out this week in the Journal of Neuroscience. [Jenny Tong et al., "Ghrelin Enhances Olfactory Sensitivity and Exploratory Sniffing in Rodents and Humans"]

First, scientists injected rats with ghrelin, and videotaped their noses. Their sniffers ran on overdrive for several hours following the injection. And the rats could detect fainter scents, too.

So then the researchers called in nine fasting humans, to see if our sniffing powers get a boost from ghrelin. The volunteers took whiffs of various substances—like baby powder, tomatoes and rosemary chicken. And regardless of how appetizing each aroma was, the volunteers took deeper whiffs—even of plain air—after getting a shot of ghrelin.

All of which suggests we’ve evolved a number of tricks to avoid the ultimate game-over: starvation. Because knowing you’re famished is only half the battle. Actually tracking down that wooly mammoth? That’s what really counts.

—Christopher Intagliata

[The above text is an exact transcript of this podcast.]