According to a study, giant insects that once ruled the Earth met their end because of the first birds. The evolution of birds forced insects to become smaller.
Giant insects used to dominate the Earth about 300 million years ago from now. The largest fly had wingspans of up to 28 inches which is slightly smaller than a crow's. Matthew Clapham, who is the study co-author, mentioned this in his study. This fly is a dragonfly-like griffinfly . Claphan and a colleague created a database of wingspan that includes more than 10,500 insect fossils from the past 320 million years.
The secret behind these giant insects that shrunk to modern size is hidden in the atmosphere of that time. The high level of oxygen is a part of the prehistoric atmosphere that boosted their growth. "These flying insects need lots of oxygen to support their flight muscles," Clapham said. "And since their breathing tubes are inefficient, they need high atmospheric oxygen levels to grow large. The more oxygen in the environment, the more muscle mass the insect can provide oxygen for and the larger the insect can be."
Things started to change around the same time when birds first appeared from dinosaurs. "The argument that we're making is that oxygen is important and a limiting factor on insect size," Clapham said. "But once birds evolved, they became a more important constraint on the maximum size of insects."
Over time, the birds started to fly quickly with better maneuvering that made the large insects their food. Clapham believes the birds may have eaten small insects like the modern birds do these days. A second fall in insect size may be related to the event that slayed the dinosaurs.
The study indicates that birds are the ones that saved people from the giant insects. "The largest insects today could perhaps be three times as large as they currently are," Clapham said this based on current oxygen levels. "That doesn't mean that every insect today would be three times as big, but the [growth limit] could rise, and there could be larger ones." added Clapham.
