Spider-Man could not do whatever a spider can, latest research indicates.
In a blow to fans of the web-slinging superhero, scientists have found the sticky footpads that make spiders, tree frogs and geckos such adept climbers are restricted by body size.
Far from arriving at the scene of a crime just in time, the friendly-neighbourhood crusader would struggle to scale a bungalow let alone a skyscraper.
Researchers calculate a person would need sticky pads covering 40% of their body to climb buildings like the comic book character.
This would require the lycra-clad crusader to have unfeasibly large feet, taking a European shoe size of 145, or US size 114 - a likely impediment to a fleet-footed crimefighter, whose only apparent reward is action.
As part of their study, the researchers compared the weight and footpad size of 225 climbing animal species.
Their work could help in the development of new adhesives.
Lead scientist Dr David Labonte, from Cambridge University's Department of Zoology, said: "As animals increase in size, the amount of body surface area per volume decreases - an ant has a lot of surface area and very little volume, and a blue whale is mostly volume with not much surface area.
"This poses a problem for larger climbing species because, when they are bigger and heavier, they need more sticking power to be able to adhere to vertical or inverted surfaces, but they have comparatively less body surface available to cover with sticky footpads.
"This implies that there is a size limit to sticky footpads as an evolutionary solution to climbing - and that turns out to be about the size of a gecko."
The scientists found tiny mites use around 200 times less of their total body area for adhesive pads than geckos.
Creatures bigger than lizards have found alternative climbing solutions, such as gripping toes and claws.
Dr Labonte said: "We were looking at vastly different animals - a spider and a gecko are about as different as a human is to an ant - but if you look at their feet, they have remarkably similar footpads.
"Adhesive pads of climbing animals are a prime example of convergent evolution - where multiple species have independently, through very different evolutionary histories, arrived at the same solution to a problem.
"When this happens, it's a clear sign that it must be a very good solution."
The research, published in the journal Proceedings of the National Academy of Sciences, suggested one solution to the scaling problem might be having much stickier adhesive footpads.
Co-author Dr Christofer Clemente, from the University of the Sunshine Coast in Australia, said: "We noticed that within closely related species pad size was not increasing fast enough to match body size, probably a result of evolutionary constraints. Yet these animals can still stick to walls.
"Within frogs, we found that they have switched to this second option of making pads stickier rather than bigger.
"It's remarkable that we see two different evolutionary solutions to the problem of getting big and sticking to walls."
0 nhận xét:
Đăng nhận xét