Large Bugs

358 million years ago insects got really big. Millipedes and centipedes were larger than humans, dragonflies grew big as eagles and beetles were the size of a large dog. The leading theory behind ancient bugs getting so big is that they benefited from a surplus of oxygen in Earth's atmosphere. Earth became abundant in oxygen because trees were new on the scene and they were able to grow because of lignin. But when these trees died there were no organisms to could break down lignin so trees kept putting oxygen in the atmosphere but didn’t “balance the books” by releasing CO2 when they died.