The ovary is a time machine. It travels to the future, reaching old age ahead of the rest of the body. At birth, each ovary contains around a million follicles—tiny, fluid-filled sacs that hold immature eggs. But the decline of these follicles is immediate and unceasing. By puberty, only about 300,000 remain. By age 40, the vast majority are gone. And by 51, the average age of menopause in the United States, virtually none are left.
Humans are an oddity in this regard. Most mammals remain fertile up to the end of their lives; the only species known to experience menopause naturally are. In humans, the loss of hormones during menopause sets off a cascade of negative health effects: Bones get brittle; metabolism slows; and the risk of , and increases. Paradoxically, women live longer than men on average but .
Jennifer Garrison has a hunch that the ovaries are the culprit. “That cocktail, that orchestra of chemicals that the ovaries make, is really important to overall health,” says Garrison, an assistant professor at the Buck Institute for Research on Aging in Novato, California. “When it goes away at menopause, it has a dramatic effect.” On the other hand, having working ovaries for longer seems to carry longevity benefits. One study of 16,000 women found that later menopause made it more likely.
Despite the fact that half the world’s population experiences ovarian aging—including cisgender women and trans and nonbinary people—longstanding gender bias in science means it has remained an understudied field. But that’s starting to change.
Garrison is a member of the Buck Institute’s Center for Reproductive Longevity and Equality, a first-of-its-kind facilitywith a $6 million gift from attorney and philanthropist Nicole Shanahan. In 2019, she helped launch a related effort, the , to fund outside researchers. An initial 22 researchers received inaugural grants totaling $7.4 million. Their goal is to understand why the ovaries seem intricately connected to health and longevity. Unraveling these mysteries could mean extending a person’s reproductive years—and potentially lifespan—by delaying menopause.
In 2018, the field of reproductive longevity was so nascent that Garrison had a hard time finding faculty to interview, let alone hire, to staff the center. Few people were actively researching it, partly because the only other mammals that experience it are whales—which can’t exactly be studied in a lab. It’s also hard to study ovarian aging in such long-lived species—killer whales, for example, can live up to 90 years in the wild. Instead, researchers have often tried to crack menopause and its link to aging by proxy: by observing chemotherapy’s effects on fertility, by studying a common menopause treatment that mimics female hormones, or by experimenting on mice, which are imperfect stand-ins for humans.
Five years later, the Buck Institute’s efforts are starting to deliver results. Researchers might not have figured out how to slow reproductive aging yet, but they’ve spurred interest in a long-overlooked organ and opened a new avenue of inquiry that could have implications for how everyone ages—not just people with ovaries. “If we can understand what’s happening in the ovary,” Garrison says, “that will probably tell us something about aging in the rest of the body, and could also give us a handle on how to intervene.”