Sorry Spider-Man, you’re just too big to stick to walls
Study finds upper size limit to sticking to walls, and that if it were up to evolution, Spider-Man would have massive, funky-looking feet.
The ability to crawl up vertical walls is not only cool, but also a huge advantage to escape being eaten or to surprise prey. Many species have arrived at this conclusion and found different ways of acquiring the super power (unlike Marvel’s Spider-Man, who was bitten by a radioactive spider). A new study recently published in PNAS shows that nature offers variations to vertical climbing - basically, either you are super sticky or freakishly big-footed.
Researchers compared the weight and foot size of 225 climbing species, ranging from tiny mites and spiders to tree frogs and geckos, and found that the bigger and heavier the animal is, the larger the feet need to be. The gecko, with its large sticky footpads, climbs away with the title of largest animal with the wall-climbing super power.
Animals do not seem able to get bigger than gecko-sized if they want to keep their supreme skill. “There is a size limit to sticky footpads as an evolutionary solution to climbing” says lead-author David Labonte of the University of Cambridge, “and that turns out to be about the size of a gecko."
For humans to be able to climb up walls, we’d have to evolve feet that took us up just a few shoe sizes - to about a UK 113 to be precise! That, or have impractically sticky feet. To be fair to Spider-Man, he is not a product of evolution, but one of human imagination, so there is really no reason why he should stick to laws of physics. He can do whatever he likes…
If having big feet does not sound appealing, then nature offers another solution: more stick-power. When evolution finds multiple, independent answers to the same question it means that it’s an exceptionally cool skill. For frogs, it was found that they had evolved to make 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,” says co-author Christofer Clemente of the University of the Sunshine Coast.
Maybe, humans can learn super powers from animals when developing large-scale adhesives. “There is a lot of interesting work still to be done looking into the strategies that animals use to make their footpads stickier," says Labonte. “These would likely have very useful applications in the development of large-scale, powerful yet controllable adhesives”.
So all we can say is sorry Spider-Man, don’t let all this bring you down…