Giant Bugs of Ancient Earth Didn't Need Extra Oxygen to Grow Huge

Scientists thought giant prehistoric insects could only grow so big because Earth had more oxygen in the air back then, but a brand new study says that's wrong! It turns out these enormous dragonfly-like creatures had super-efficient breathing systems that didn't need extra oxygen at all, so now scientists have to figure out what REALLY made them grow to giant sizes—maybe it was fewer predators, or maybe their bodies just couldn't get any bigger no matter what.