Three million years ago giant insects rule the earth

Biology is not a fair history of the war, if they have more atmospheric oxygen, now rule the Earth would not be human but insects.
Scientists said that if the Earth's atmosphere there is more oxygen, then the Earth's surface or air will be filled with enormous insects.
Scientists believe that at about 3 million years ago, life on Earth has a lot of giant insects. Hawks general, as the size of dragonflies flying in the air, they have a 2.5-foot-long wings. In that period, the earth's atmospheric oxygen content which accounted for 35%. Now the atmosphere which we breathe the oxygen content of only 21%.
Of course, at that time not all of the insects are so great. Arizona Midwest insect physiologist at the University of Alexandria, Keyser said : "But still there may be about 10% of the giant insects."

Deep breaths

In order to clarify whether the air oxygen more insect vision, the greater Keyser and his colleagues examined whether our current atmospheric limit the size of insects. They compared the size of the 0.1-inch to 1.5-inch between the five different types of insects. In particular, the researchers studied the insects for breathing air out of the trachea in vivo. Only one of our human trachea, but insects have a complete and mutually connected to the trachea respiratory system.

X-rays showed that, when the beetles grow larger, their trachea occupy their physical size will increase, which represents about a body volume of 20% more. That is because when the insects grew too large, they need more trachea to provide more oxygen necessary.

Constraints

But ultimately, trachea not exceed a certain size. Researchers calculated that the size of insects not more than six inches. And some of the largest South American beetles from the big Titan ALB considerable size.

They argued that if the Earth did in the past and the atmosphere is more oxygen, then the trachea of insects can become smaller, because even a small change is still able to provide them with enough oxygen, Keyser that such insects by reducing the restrictions on the volume will become bigger.

Scientists in this week's National Assembly physiology made this latest discovery.