Horseshoe crabs are fascinating creatures, and not just because they look like some kind of shelled alien.
First of all, horseshoe crabs aren’t crabs at all. They’re actually more closely related to spiders and scorpions than crabs and lobsters. Secondly, they are ancient—even predating the dinosaurs—which is why they’re often referred to as “living fossils.” Third, their blood contains a unique substance called limulus amebocyte lysate (LAL) that humans have relied on for decades to test the safety of medications, vaccines and medical equipment. (A synthetic version of LAL is increasingly being utilized instead, which is good news for horseshoe crabs who probably don’t appreciate the bloodletting.)
Oh, and they also glow also under ultraviolet light (blacklight) like scorpions do, and nobody knows why.
But one of the most interesting recent discoveries about horseshoe crabs is that their brains haven’t evolved much at all in over 300 million years. In 2021, a 310-million-year-old horseshoe crab fossil was discovered in Illinois with a beautifully preserved brain. Scientists compared it to a current species of horseshoe crab and found that while their external characteristics had changed over time, their brains were pretty much identical.
That discovery makes a viral video of one horseshoe crab seeming to go all out to help another one all the more remarkable. Horseshoe crabs usually use their tails to flip themselves over if they end up upside down, but a video shows a horseshoe crab clearly exerting sustained effort to help a buddy who is flailing on its back. Such behavior seems to indicate some combination of planning and altruism, which are characteristics we usually associate with highly social or evolved creatures. If horseshoe crab brains haven’t evolved in hundreds of millions of years, what would compel one to to help another with no obvious benefit to itself?
Maybe horseshoe crab brains were just perfect for their species’ purposes from the get-go—10/10, no notes—and this video is just a fluke. Or perhaps what we’re witnessing is biological altruism, which is a behavioral reality of some species of animals, usually among those with complex social structures. Scientists debate whether biological altruism differs from human altruism since our motivations to selflessly help others frequently go beyond our species’ survival, and research on that front is ongoing. While the “why” here may be a mystery, it doesn’t make it any less heartwarming to see an animal that we think of as purely instinctual go out of its way to help another.
Plus, in this case, the rescue is truly riveting. People have commented that they keep tilting their phones to try to help them out. Watch:
If a creature whose brain hasn’t evolved in 310 million years can do this for one another, surely we can treat our fellow humans with care and compassion, no?