At some point, all of you have dreamt about being Spider-Man. Those dreams will stay entirely fictional, unfortunately. Scientists have confirmed this will never be physically possible because humans are too big, and have feet that are too small for the job.
In a study published in the journal PNAS this week, biologists from the University of Cambridge’s department of zoology explain a correlation between the size of an animal and the size of adhesive limbs needed to support it. For ants, only 0.09% of their body needs to be adhesive to walk up walls. For a gecko, this goes up to 4.3%. But for humans, this rockets up to 40%, or 80% if you want to support your whole body!
"If a human, for example, wanted to climb up a wall the way a gecko does, we’d need impractically large sticky feet — and shoes in European size 145 or US size 114," Walter Federle, senior author from Cambridge’s department of zoology, commented in a press statement.
This could be fixed by making your entire body an adhesive pad, but then how would you move? Pushing yourself up with feet would mean having to remove yourself from the wall, immediately resulting in you falling to your death. What's important here is the volume and surface area of an animal don't increase at the same rate. Our feet are much smaller in proportion compared to that of an ant's.
"This poses a problem for larger climbing animals," adds David Labonte, a senior author from the same department. "Because, when they are bigger and heavier, they need more sticking power, but they have comparatively less body surface available for sticky footpads."
So what is the fix? If the adhesive pad isn't going to increase anytime soon (damn you, rate of evolution), then we'd need more adhesive pads. So think more Doctor Octopus, and less Spider-Man.