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The Caveman Controversy

In her new book, Paleofantasy, Marlene Zuk dared to debunk a lifestyle that advocates eating, exercising, and even mating like our ancestors. Now the outspoken insect-sex researcher has adversaries, who say she’s the one whose thinking needs to evolve.

The Caveman Controversy
Photo by Michael Jacobsen (Illustration)

(page 3 of 5)

Zuk and her colleagues use these crickets for all sorts of “wacky” experiments, she explains, including raising some in silence and others in a world of sound to see how various auditory environments affect mating behavior. Crickets may seem too different from humans to offer windows into our lives, but that’s the point, she says. You can’t anthropomorphize bugs, which makes it easier to be objective about the scientific insights they offer—including the ones that came out of a startling breakthrough Zuk made a decade ago in a dark, silent field in Hawaii.

On a typically warm, post-sunset evening on Kauai in 2003, Zuk hopped out of a car, strapped on a headlamp, and walked onto a grassy lawn. It was an ideal environment for crickets, but the field was chirp-free. Zuk hadn’t expected to see any of the insects hopping around; over the previous decade, she had watched the island’s cricket populations decline rapidly as a result of parasitic flies that dive-bomb singing males and deposit larvae inside their bodies. Once inside, the wormlike maggots eat their hosts alive and then burrow out, leaving the dying crickets behind.

Zuk’s study of the system began in the early 1990s, when she traveled to Hawaii for a conference and decided to pluck some crickets from a field and dissect them in a “quasi-recreational way.” (It “seemed amusing at the time,” she recalls.) Sure enough, her investigations revealed fat, white larvae wriggling inside some of the crickets. Zuk’s good-spirited husband, John Rotenberry, a bird biologist also at the U of M, was along on the trip and was surprised by the discovery. ”I always claim it’s the only time he’s been impressed with my scientific acumen,” Zuk jokes.  

As she continued to visit Kauai over the years, it seemed clear that the parasites were winning. By 2001, Zuk heard only one calling male in her routine field visits and found just a few crickets remaining. So when she arrived on that night in 2003, she nearly decided not to even look. It was just so quiet. But she had come a long way, and so she got out of the car. “In my headlamp, I started seeing all these crickets,” Zuk remembers. “We ended up finding way more crickets than we had imagined. But they weren’t calling. That was just bizarre.”

Male crickets use their distinctive chirps to attract mates, and the discovery of silent crickets was puzzling, even to a researcher who had studied them for 20-plus years. Even more surprising was Zuk’s subsequent discovery that the Hawaiian crickets hadn’t just learned to stop singing to escape detection by parasites; they had actually lost the parts on their wings that allow them to make noise. The change came from a single gene mutation that spread through the population in just 20 generations over five years—the equivalent of a few centuries in human years. According to a traditional understanding of evolution, such significant genetic changes should take hundreds or thousands of human-equivalent years, making crickets one of the faster cases of evolution ever observed in the wild.

Zuk’s realization that evolution can happen so quickly in crickets led her to collect case studies of rapid evolution in fish, birds, snakes and, yes, people. From there, she developed a bold theory that inadvertently pissed off a lot of people.

Veins bulge out of Alicia Kleppinger’s lean, steely arms as she lifts the floppy menu at Brasa, a go-to destination for the Twin Cities Paleo community for its locally soured, high-quality meat. After starting an internship at CrossFit St. Paul two years ago, Kleppinger, 32, joined one of the gym’s 30-day challenges to eat Paleo. It was hard at first to resist donuts and other sweets, she says, and in the beginning, she found herself irritable, foggy, and hungrier than usual. But after a week and a half, she started to feel better than ever. Her energy held steady throughout the day. She stopped having monthly mood swings. Her seasonal allergies cleared up. Though Kleppinger was not trying to drop weight, she lost a few pounds.

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