The prehistoric insects were gigantic, with some species, such as the dragonfly, reaching wingspan of as much as 70 centimeters, but the arrival of predators forced them to shrink. The study, published in the journal Proceedings of the National Academy of Sciences and conducted by two American researchers, Matthew Clapham and Jered Karr, of the University of California at Santa Cruz, reveals how those that are today among the smallest creatures on Earth.
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Insects from prehistoric times were gigantic, with some species, such as the dragonfly, which reached wingspan of 70 centimeters, but the arrival of predators forced them to shrink. The study, published in the Proceedings of the National Academy of Sciences and conducted by the two American researchers, Matthew Clapham e Jered Karr, of the University of California at Santa Cruz, reveals how those who are today were made 300 million years ago the smallest creatures on Earth.
Experts, who have come up with one database of over 10.500 fossil insects and that covers approx 320 million years, speculate that the enormous size of prehistoric insects was favored from the increase in atmospheric oxygen levels, available up to 30%. “As the oxygen increased, the insects got bigger. When it decreased, their size shrank, "Clapham said. paleobiologist at the University of California.
When, in fact, 150 millions of years ago, during the Jurassic period, things changed with the appearance of the first birds, winged insects stopped growing. “We believe that oxygen is an important and limiting factor for the size of insects. But once the birds evolved, they became one much more binding factor for the maximum size of the insects“, Continues the researcher.
Giant insects would have fallen prey to birds for a very specific reason: “the maneuverability of any flying object depends on its size. Small objects are much more manageable than large ones. " Like this large insects would have been easy targets. But it's also possible that giant birds and dragonflies may have been competing for the same food.
Perhaps we will never know, but what, in conclusion, is certain is that if it weren't for birds, modern insects would probably be much larger: based on current oxygen levels “the largest modern insects today could be even three times larger than they already are. This does not mean that today all insects would be giants, but by increasing the limit size some could have been bigger ", concluded the paleobiologist.
Roberta Ragni
Foto e fonte: National Geographic
