Eileen Karpfinger
1.3K posts














Over the last 250 million years, at least five completely unrelated lineages of crustaceans have independently evolved into crab-like forms, a phenomenon so common that biologists gave it its own name: carcinization. And despite decades of study, scientists still don’t fully understand why it keeps happening. Detailed evolutionary research shows that “crabbiness”, the distinctive wide, flattened body, tucked tail, and armored shell, has appeared, disappeared, and sometimes reappeared across different branches of the crustacean family tree. In one of the strangest cases, king crabs actually re-evolved crab-like traits after their ancestors had already lost them (a process called decarcinization). This repeated convergence suggests the crab body plan offers powerful survival advantages. Crabs are incredibly successful and adaptable, thriving in virtually every marine and coastal environment on Earth — from coral reefs and rainforests to deep-sea vents and underground caves. Their sideways scuttling allows quick directional changes while keeping an eye on predators, and their hard exoskeleton provides excellent protection. Yet the mystery remains: some crab-like species walk forward, others have ditched the shell entirely, and plenty of non-crab crustaceans do just fine without ever evolving into crabs. The real fascination for biologists lies in what this tells us about evolution itself: under certain environmental pressures, nature seems to repeatedly converge on the same highly effective solutions — almost as if the crab shape is one of evolution’s favorite “optimal” designs. [“One hundred years of carcinization – the evolution of the crab-like habitus in Anomura (Arthropoda: Crustacea).” Biological Journal of the Linnean Society]



Most primary care is unnecessary: -LDL does not cause heart disease. -Blood pressure targets are too low. -Colonoscopies and mammograms do not improve mortality. Going to a doctor if you're feeling well is generally a scam.









The Great El Salvadorian Comeback - God, Bukele, & Bitcoin. Ryan Matta Documentary. May 26th, 2025








