That’s because the female body is built for resilience and longevity, as CNN found while conducting research for a new book, “The Stronger Sex.”

Even with intricate reproductive systems and the challenging, occasionally life-threatening processes such as menstruation, pregnancy, childbirth, and breastfeeding, female bodies generally have greater longevity compared to male bodies.

“In populations where men and women had the same lifestyle, there was still a difference in mortality — women had a higher life expectancy than men.”

Recent studies suggest that the advantage women have isn’t solely due to genetics and hormones; it is also deeply rooted in the physical structure of their bodies.

At North Carolina State University, a team led by microbial ecologist Erin McKenney and forensic anthropologist Amanda Hale conducted a landmark study measuring the lengths of the small intestines in cadavers for the first time since 1885.

The team discovered that women’s small intestines were significantly longer than men’s — an advantage that allows women to extract more nutrition from the same quantity of food.

This finding, published in the journal PeerJ in a 2023 paper, might be explained by the extra demands on female bodies throughout human history: “The vast majority of the nutrients you need to replenish your system — especially during reproduction and nursing, like protein and fat — that’s what’s being absorbed by your small intestine,” Hale said.

This could be a key piece of the “Female Buffering Hypothesis” — the idea that female biology evolved to withstand environmental and physiological stress better — according to Hale.

Traditional medical research has long ignored the complexities of the female body. As these genomic and physiological functions are better studied and understood, the drivers behind the strength and resilience of the female body will come into focus.

This knowledge will inform more targeted treatments for infection and immunity—for all bodies.