The last 450 million years haven’t necessarily been kind to horseshoe crabs, the spiky-shelled specimens that crawl out of the Atlantic Ocean onto Cape Cod beaches to mate under the full moon. Hostile ice ages and thundering dinosaurs notwithstanding, the hardy limulus polyphemus somehow managed to thrive, so much so that shellfishermen considered them an important part of the intricate ecosystem on the ocean floor.
Yet over the past two decades, the horseshoe crab population has dwindled at an alarming rate, according to data compiled by the Wellfleet Bay Wildlife Sanctuary and others. The agent of this destruction: humankind, in service of the modern biomedical industry and its voracious appetite for the weird, blue-tinged horseshoe crab blood that is critical for testing the safety of almost all modern medical devices. Fortunately for the beleaguered crabs, however, biomedical advances in the lab might also save it: A synthetic substitute has been available for more than a decade, as Sarah Zhang wrote this spring in The Atlantic. That not only portends well for bipedal detente with the other living, breathing creatures around us, but maps a path to a cruelty-free future where most, if not all, biomedical tests examine molecules in a lab, not primates in a cage.
The animal kingdom has always contributed to biomedical knowledge, and throughout history, animal lives have been sacrificed for medical tests needed to detect and abate human diseases. Take, for example, the hoary expression “The rabbit died,” a euphemism that meant “I’m pregnant” in decades past. Folkloric terms often serve as shorthand for complex advances and rapid changes in social norms, and that’s the case here: In the 1920s, researchers discovered that a woman begins producing a hormone known as hCG after a fertilized egg implants itself in the wall of her uterus. They also found that urine from a pregnant woman, which contains hCG, caused ovarian changes in female rabbits — making the rabbit test a reliable indicator of pregnancy for the Jazz Age and beyond. Unfortunately, the rabbit always died in the early days because the bunny in question had to be killed to extract its ovaries.
Pregnancy detection methods began to change in later decades as scientists developed ways to measure hormones, and in the 1970s the early pregnancy test was approved. This new wave of in-home testing, which bypassed the doctor’s office, afforded women a new level of privacy and became part of a wider cultural awakening about reproductive health. But a scientific revolution was taking hold as well: the development of DNA sequencing and the mapping of the human genome. Now scientists don’t always need animal models. Insulin production has been consigned to bacteria farms rather than live pigs and, in 2015, the government extended endangered species protection to chimpanzees in research labs, allowing our closest relative in the animal world to retire.