Despite the controversy in some issues, evolution still works very well within the physical limitations of each individual species of living being. One of these limitations, for example, is size, which in turn is the reason why some physical features are present in some animals and completely absent in others.
One such feature is, for example, the ability to cling to vertical surfaces, which is found in some species of amphibians, reptiles, and mammals. But if this ability is so useful, then why is it not in larger animals, for example, in humans? In other words, why there are no real "spidermen"?
The answer to this question is very simple: all because a person, as a species, is too large (or large, if you will) to possess such a feature. In a study published in the scientific journal Proceedings of the National Academy of Sciences (PNAS), biologists from the Department of Zoology at the University of Cambridge explain that the larger the animal, the greater the surface of its body must have coupling force, or van der Waals force, which helps the same geckos cling to vertical surfaces. In other words, the bigger you are, the much larger and sticky limbs you need to have to crawl along the wall.
If an animal is about the size of an ant, then only 0.09 percent of its body is required to be covered with a sticky surface in order to walk on the walls. For a gecko, this figure should already be 4.3 percent, and for a person in this case it will take 40 percent, or 80 percent, if only one part (half) of his body is used.
“If a person wants to crawl on the walls in the same way as a gecko does, he will need larger legs, or rather feet of 145 size,” says Walter Federley, senior author of the study from the zoology department of the University of Cambridge.
If the entire front of the body is sticky, then how will you climb the wall? Each time you raise your hand or foot to make further movement, you will fall - the area of the coupling surface between your body and the wall will be insufficient to hold your body weight on the wall.
The essence of the problem lies in the fact that the volume and area of the adhesive surface do not increase proportionally, but rather decrease. The larger the animal, the smaller its coupling surface becomes, but at the same time the strength of the stickiness itself may increase.
“This creates problems for larger animals,” says David Labonte, another author of the published study.
“The bigger and heavier the animal, the more van der Waals force it needs, however, as a rule, they have a relatively smaller available body area for the sticky zones,” Labonte adds, explaining how nature limits act on the size of animals. and how large these sticky zones can be, until the animal has to make too much effort to use them.
Of course, this study only affects sticky abilities found in nature. And when using artificial materials, the area required for being able to stay on vertical surfaces can, in theory, be reduced. Labonte, Federly and their colleagues note in their study that they were able to even detect some species of animals whose size and adhesive parts did not correlate at all in proportion to each other — their bodies grew faster than the area of sticky zones increased. Compensation in this case was the stronger stickiness of these zones. All this means that a person may never be able to independently, using only his hands and feet, crawl along the walls. However, no one says that we can not do it with the help of special artificial materials and devices.
The article is based on materials .
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