For decades, women have been told the same story:

You’re born with all the eggs you’ll ever have.

From birth onward, that number steadily declines until menopause, when the ovarian reserve is thought to be exhausted.

But over the last two decades, a growing body of research has challenged that idea. While many questions remain unanswered, scientists are exploring whether the ovary may be far more dynamic than we once believed.

Here’s what we know—and what is still being debated.

The Traditional View

Medical textbooks have long taught that women are born with approximately 1–2 million immature eggs.

By puberty, that number has fallen to roughly 300,000–500,000.

Only about 400–500 eggs are ovulated during a woman’s reproductive years, while the vast majority naturally undergo a process called atresia (programmed cell loss).

This understanding has guided reproductive medicine for generations.

The Research That Challenged Everything

In 2004, reproductive biologist Jonathan Tilly and his colleagues published a groundbreaking study in Nature suggesting that adult mouse ovaries contained cells capable of generating new oocytes (egg cells).

The findings challenged one of reproductive biology’s oldest assumptions.

The paper sparked intense scientific debate—and it still does today.

Subsequent research identified cells in human ovaries with characteristics similar to stem cells, often called ovarian stem cells (OSCs) or oogonial stem cells.

In laboratory settings, researchers have demonstrated that these cells can:

• Express markers associated with germline cells
• Differentiate into egg-like cells
• Form early follicle-like structures under specific experimental conditions

These discoveries opened an entirely new area of reproductive research.

But Are These Cells Making New Eggs Inside the Human Body?

This is where things become much more nuanced.

Although ovarian stem cell-like populations have been identified and studied in laboratories, there is currently no scientific consensus that these cells routinely produce functional eggs inside adult human ovaries.

Many reproductive biologists remain skeptical because:

• Human studies have not conclusively demonstrated ongoing egg production in living ovaries.
• The laboratory environment is very different from the human body.
• It has not been proven that these cells generate eggs capable of resulting in healthy pregnancies naturally.

In other words:

The existence of ovarian stem-like cells is intriguing. Their role in natural fertility remains unproven.

The Ovary May Be Aging More Than the Eggs

One concept from Jonathan Tilly’s later work has generated considerable interest.

He has suggested that ovarian aging may not simply be about running out of eggs.

Instead, the ovarian environment—sometimes called the ovarian niche—may become less supportive over time.

Think of it like a garden.

Healthy soil helps seeds grow.

Poor soil doesn’t necessarily mean the seeds are gone—it means the environment no longer supports them.

Scientists are actively studying whether factors such as:

• Chronic inflammation
• Oxidative stress
• Reduced blood flow
• Mitochondrial dysfunction
• Hormonal changes
• Fibrosis
• Immune system changes

contribute to ovarian aging.

While these factors almost certainly influence ovarian health, it has not been established that improving them causes women to make new eggs.

Menopause Doesn’t Mean Every Egg Is Gone

Another surprising fact:

Women entering menopause may still have hundreds to around one thousand immature follicles remaining in their ovaries.

These follicles generally no longer respond adequately to hormonal signals required for normal ovulation.

Researchers believe menopause occurs because the remaining follicles become insufficient in number and quality, along with changes in hormonal communication between the brain and ovaries—not simply because the ovary reaches absolute zero eggs.

This distinction is important.

Can We Improve the Ovarian Environment?

This is one of the most exciting areas in longevity medicine.

Researchers are studying interventions that may support ovarian function by improving overall cellular health, including:

• Blood sugar regulation
• Regular exercise
• Anti-inflammatory nutrition
• Adequate protein intake
• Sleep optimization
• Stress reduction
• Maintaining healthy insulin sensitivity
• Supporting mitochondrial function

Experimental therapies under investigation include:

• Ovarian tissue transplantation
• Platelet-rich plasma (PRP)
• Stem-cell–based approaches
• Mitochondrial therapies
• Senolytics
• Rapamycin
• NAD⁺ metabolism
• AMH modulation

Most of these approaches remain investigational and are not yet established treatments for restoring fertility or reversing menopause.

What This Means for Women’s Health

The biggest takeaway isn’t necessarily that women are making new eggs today.

It’s that scientists are beginning to understand ovarian aging in a much more sophisticated way.

Instead of viewing the ovary as a simple “egg countdown clock,” researchers now recognize that:

• The ovarian environment matters.
• Cellular health matters.
• Metabolism matters.
• Inflammation matters.
• Blood flow matters.
• Mitochondria matter.

Whether future therapies will successfully harness ovarian stem cells or rejuvenate the ovarian environment remains one of the most exciting questions in reproductive medicine.

The Bottom Line

Researchers have identified stem cell-like populations in adult ovaries and have shown remarkable results in laboratory experiments. However, there is no consensus that adult women naturally regenerate functional eggs throughout life.

What is becoming increasingly clear is that ovarian aging involves much more than simply “running out of eggs.” The health of the ovarian environment appears to play a significant role in fertility, hormone production, and reproductive longevity.

As research continues, our understanding of menopause and ovarian aging may evolve dramatically.

For women interested in preserving fertility and supporting healthy aging, the future may lie not only in protecting the eggs themselves—but in protecting the environment that allows them to thrive.

Want to Go Deeper on Ovarian Longevity?

If the idea of protecting your ovarian environment resonates, there's another piece of the puzzle worth exploring: spermidine.

This naturally occurring compound has become one of the most talked-about molecules in longevity science — and new research is looking specifically at its role in slowing ovarian aging.

Read: Spermidine & Ovarian Longevity →