Animal studies are the backbone of medical and scientific research. Because of animal testing, humans have developed vaccinations for smallpox, nearly eradicated polio, discovered chemotherapy, and made countless other innovations across the medical spectrum. But there’s a major flaw in the way we conduct these experiments: Far too many animal tests ignore biological sex entirely.
A new study from the Wellcome Trust Sanger Institute, published in Nature Communications, argues that too many animal experiments have failed to take into account sexual dimorphism—the traits that differ between sexes in a species, from size to bone density to coloring. This blind spot may be skewing the results of animal testing. And that could have big consequences for the conclusions that we take from animal studies and apply to humans.
Science has a long history of making incorrect assumptions about biological sex that skew testing on live subjects. For much of history, scientists have tended to regard female bodies as simply scaled-down versions of males, which meant that one could just test on men and draw conclusions about women’s medical needs. This has backfired repeatedly. In one notable case, in 2013, the US Food and Drug Administration had to cut the recommended dosage for zolpidem (Ambien) for women by half after it was discovered that taking a “normal” dose often resulted in serious overdoses for women.
At the same time, scientists thought female bodies were too complex and variable to be reliable test subjects, owing to monthly hormone cycles and menstruation. As it happens, male test animals show as much hormonal variation as female animals, so that argument has since been disproven. We also now know that the female body, in many ways, operates differently than the male body. New evidence this week shows that female brain patterns are more active than men’s, a revelation that joins a corpus of science proving that women, far from being “tinier men,”…