Franklin D. Roosevelt no doubt meant to be soothing when he insisted, “The only thing we have to fear is fear itself.” A quick and terrifying tour through the academic literature on fear, though, reveals just how much heavy lifting that only was doing.

Our fears run broad and deep, and are every bit as diverse as we are. The 2017 version of Chapman University’s Survey of American Fears tabbed “corruption of government officials” as the most common fear, afflicting nearly 75 percent of respondents; concerns about the health-care system, the environment, personal finance, and war also figured in the top 10. Such spine-tingling triggers as public speaking and enclosed spaces landed in the bottom half of the 80 fears polled; clowns were slightly more scary than zombies, who were only slightly more scary than ghosts.

One reason we struggle with fear is that we’re simultaneously too primitive and too evolved for our own good. Our lizard brains are ruthlessly efficient: Signals speed to the threat-sensing amygdala within 74 milliseconds of the slightest hint of danger. [1] This speed has, over eons, helped save us from extinction. But it’s also led to plenty of false alarms.

Part of the problem is that our forebears’ oldest fears are still with us. Even babies exhibit a fight-or-flight response to pictures of snakes and spiders, presumably as a result of instinct rather than experience. [2] Deep-seated aversions like these are strong enough to distort our sense of reality: People with arachnophobia are likely to overestimate the size of spiders relative to other organisms. [3] Such ancestral sensitivities may also account for trypophobia, the fear of closely clustered circles (such as pores in sponges or bubbles in coffee)—which, according to one study, may affect up to 16 percent of the population. Research by two groups of psychologists in the U.K. proposes that small circles’ resemblance to parasites and to distinctive patterns on poisonous animals may be enough to trigger this atavistic response. [4, 5]