Why science has failed women (and how we can change it right now)

As a predoctoral researcher, I study the aging of hematopoietic stem cells – the cells responsible for regenerating all our blood throughout life–. A few years ago, while observing these cells under a microscope, I noticed some strange differences between my samples. They were supposed to behave identically, as they all came from donors of the same age, but this was not the case. I remember a thought coming to my mind: "Are these donors of the same sex?". Until that moment, I had never asked myself this question. When I started reading the scientific literature, I realized this wasn't just my blind spot. For centuries, both basic research and modern medicine have operated under the premise of the "standard human": the Reference Man. This wasn't done as a conspiracy theory to exclude women from research, but out of a combination of convenience and practicality. Early medical researchers used military records of healthy male soldiers as a baseline; furthermore, scientists actively avoided studying female individuals, claiming that fluctuations in menstrual hormones would distort the data. This bias was so profound that, even in basic research, female mice were systematically excluded.

The consequences of this scientific shortcut are enormous. By reducing medicine to a single universal model – and essentially treating women as "smaller men" with different reproductive organs – it has not only harmed women: it has also made science less complete and medicine less precise. Incorporating biological diversity is not a minor correction, but a necessary condition for generating useful knowledge for everyone.

The importance of hormones

The historical exclusion of women from laboratories and medical research reveals an even deeper and more disturbing hypocrisy. Instead of viewing women's hormonal fluctuations as a vital and complex biological system that required rigorous study, science opted to ignore them.But, why?I believe the answer lies in a deeply rooted premise: because these hormonal fluctuations are "normal" for a woman's body, society has never treated them as a priority. Menstruation, pregnancy, and menopause are, in fact, normal biological events, but they have a profound and systemic impact on the functioning of the female body, and deserve the same depth of scientific study as any other major biological change, such as aging.To truly understand how deep this problem is, we need to look beyond reproductive organs. For decades, women's medicine – so-called "bikini medicine" – focused almost exclusively on breast health and gynecology. The rest of the female body was thought to function exactly like that of the reference male.

Now we know that this is not the case. We see it in cardiovascular health, where women often receive later or erroneous diagnoses because their heart attack symptoms do not reflect the classic pain observed in men. We see it in autoimmunity, where debilitating diseases like lupus and rheumatoid arthritis disproportionately affect women. We even see it in neurology, where women account for nearly two-thirds of Alzheimer's patients.

A manual written for 50% of the population

Unfortunately, our clinical guidelines still carry decades of knowledge generated from male data. Modern medicine is essentially flying blind: treating half the population using a manual written exclusively for the other half.One might think that, once aware of all that I have explained to you so far, medical innovation in women's health would become an absolute and immediate priority. Unfortunately, the medical research system cannot correct itself.We like to believe that research and science naturally flow towards areas of greatest human need, but the infrastructure is actually built on a feedback loop that traps us in a vicious cycle. Funding agencies, academic institutions, and venture capitalists allocate resources where there is already solid preliminary evidence and a proven track record of success.

Therefore, the system naturally excludes new lines of research and pathologies that have a very great impact on people, but which lack a sufficient evidence base, labeling them as "too risky" to be funded.Raising awareness alone does not solve the problem. The system requires an active and intentional choice. Funding agencies, research institutions, and investors must reserve resources for studies that rigorously incorporate the sex variable. Policymakers must mandate the use of sex-disaggregated data, and we must strengthen the integration of this evidence into our clinical guidelines. Only then can we move from a medicine based on a "standard human" to a medicine that better represents the real diversity of human bodies.