Where have all the giant-creatures’ of the world disappear that existed around 300 million years ago? Though many theories have come to the rescue of the logics muted by various scientists, but following this, yet another question does arise — why, the bugs that then grew to gigantic proportions are now rarely found on Earth?
Yes, studies have found that hundreds of millions of years ago, dragonflies grew to the size of hawks, and some millipede-like bugs reached some six feet in length! But, what leads to their present small size?
Hundreds of ideas explaining this have taken birth, but just to die at the threshold, until it is only recently, Alexander Kaiser, of Midwestern University’s Department of Basic Sciences has come up with a more convincing explanation for the change.
According to it – it was an ‘insect’s respiratory system’ that limited its size! It was all in the air, as you can say.
This is how his study explains the reasons behind the insects’ small size:
A higher concentration of oxygen in the atmosphere let dragonflies sometimes grow to the size of hawks, and some millipede-like bugs reached some six feet (two meters) in length.
It is the present decreased proportion of atmospheric oxygen that retards the bugs’ growth from reaching their earlier size or the size they can now.
It is the x-ray scan that revealed – with a beetles’ growing larger, tracheae take up proportionally more room in their bodies, with their increased need to be longer and wider necessary to deliver enough oxygen. This, in turn, leads to the crowding of other organs, stemming the growth.
So, with the still reducing-trend of atmospheric oxygen, will humans too reduce in their present average size – a few million years later? — of course, if the species survive to witness.