Despite being bitten by a radioactive spider, researchers say Spider-Man would not be able to scale walls in real life.
A recent study from the University of Cambridge found the comic book superhero, Spider Man, would need much larger hands and feet — not to mention sticky-type pads covering up to 80 percent of the front of his body — if he were to stick to and sling between city skyscrapers. Instead, researchers say geckos are the largest animals able to scale smooth vertical walls.
In other words, if humans were able to scale buildings like Spider-Man, 40 percent of our body surface would have to be covered by sticky pads, according to findings published in Proceedings of the National Academy of Sciences this week.
If a human, for example, wanted to walk up a wall the way a gecko does, we’d need impractically large sticky feet — our shoes would need to be a European size 145 or a U.S. size 114,” Walter Federle, senior author from Cambridge’s Department of Zoology, said in a news release.
For their study, researchers compared the weight and footpad size of 225 climbing animals, ranging from mites and spiders, to tree frogs, geckos and even a mammal. As animals increase in size, the proportion of body surface covered by adhesive footpads increases, thus limiting the size climbing animals can grow.
By allowing animals to climb smooth, vertical or even inverted surfaces, adhesive pads have opened up all sorts of new habitats. In fact, they’ve independently evolved multiple times in arthropods, amphibians, reptiles, and even mammals. But this adaptive trait is subject to size-dependent physical constraints. As animals increase in size, their body surface area per volume decreases; bigger, heavier animals need more adhesive power to support their weight but at some point, the amount of sticky surfaces needed becomes impractical. That’s likely why geckos are the biggest animals capable of scaling walls.
However, when the team compared closely related species of frogs, they didn’t find this disproportionate increase of pad area. Because of evolutionary or anatomical constraints, those bigger frogs had stickier pads, not bigger ones: Pad adhesion per contact area increased with size. This suggests that two different strategies have evolved to help adhesion-based climbers deal with the physical challenges of bigger body sizes.
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,” lead scientist Dr. David Labonte explained.
This simply means that bigger and heavier species need more sticking power to cling to vertical surfaces, but have less body surface available to cover with adhesive pads.
This implies 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,” Labonte added, saying larger climbing creatures have evolved alternative climbing methods, such as digging in their claws and toes.