Prehistoric times on Earth were quite different, according to fossil records the animals that inhabited our planet were extremely large compared to modern times.
The giant insects that roamed the Earth were no exception to this, because as we learned during the discussion New Antibiotic Found in Cockroaches Brains, approximately 80% of all animals on Earth are insects. There was a day that dragonflies were predatory creatures and had a wingspan similar to that of a modern seagull, but remember this was some 300 million years ago. But dragonflies were not the only giant insects during that time…
What Caused them to Become Giant Insects
According to studies, it is believed the main factor attributed to how these giant insects came to be was the amount of oxygen present in the atmosphere during those times.
Theories speculate there was extremely high levels of oxygen present and in order for the insects to survive, their bodies had to support an oxygen rich environment. So basically they adapted to grow much larger in order to absorb more oxygen from the air. This was their bodies defense for avoiding oxygen poisoning.
According to research, it’s believed that the higher oxygen levels not only effected the adult insects but the larvae were effected as well. This meant the evolution of them becoming giant began from birth.
How did the Giant Insects Use the Oxygen to Their Advantage
During the Carboniferous period, giant dragonflies and giant cockroaches were extremely common. This was partly due to the large number of lowland swamp forests that were present at the time. And as we all know, the more plant life you have, the higher the oxygen levels will be. It is believed there was approximately 30% oxygen present in the air at that time, which is nearly 50% higher than it is today.
Seeing how the oxygen was so dominant, the adult insects were able to grow larger in size and still meet their energy needs. Another study that focused on stonefly larvae showed that the higher the oxygen level is in the air, the higher it will be in the water. These stonefly larvae were similar to dragonflies in the way they started out in water before becoming adults. This being the case, it allowed scientists to see that the larval stage of development in any insect whether on land or in water could benefit from the higher concentration of oxygen.
It was also discovered that the baby stoneflies were more sensitive to the changes in oxygen than their adult counterparts. This is probably because the larvae would absorb the oxygen directly through their skin rather than having to breathe it in. This meant they had little control on how much oxygen they would take in. Where as the adults could regulate this by they opening and closing of spiracles in their body. Spiracles are just little holes on their body that are used to take in oxygen.
Even though oxygen gas is essential for any living creature here on Earth, larger quantities of it can be dangerous and even poisonous. For instance in humans, by absorbing too much oxygen, we may suffer from damage to cells which could lead to problems with vision, breathing, nausea and even result in convulsions.
Giant insects only defense to oxygen poisoning would of been to grow larger in size, this would lessen the danger associated with taking in too much. Basically the way it was explained is that the larger your body is, the smaller surface area per volume you have.
What Happened when Oxygen Levels Decreased
As we all know, the oxygen levels decreased after millions of years of Earthly development, so what happened to the insects at this point you may ask. Well there is a theory as to how the giant insects continued to thrive even after the oxygen levels decreased.
Scientists say that even though larges doses of oxygen caused an increase in body mass with these insects, a decrease in the gas would not have an immediate effect on the insects. Lower levels would not be fatal at first, but over time it’s likely that giant insects population would decrease as the generations of insects began to grow smaller and smaller in size to meet the new oxygen levels requirements.
The decrease in oxygen would cause those adult insects to become sluggish and slower. And we all know what happens to the sluggish and slow within the animal kingdom… They eventually die out, by being taken over from another dominant species. That explains why we no longer see giant insects on Earth. Although I’ve seen a few that I’d consider giant, but they are nothing near the size of a seagull.
Tell me what you think, could you imagine living in a world that still had giant insects the size of a small mammal?