I was thinking of a situation, in which there is a mass extinction that wipes out all large land animals, and after this mass extinction some of the descendants of modern geckos evolve to fill the niches left by the large mammals. Some of these descendants of geckos also evolve to walk on two legs similar to how some dinosaurs walked on two legs during the Mesozoic
I understand that human thumbs were originally used to help with climbing trees before getting used to hold things when the ancestors of modern humans started walking on two legs. Geckos use van der waals forces to help with climbing trees as they have hairs on their feet that have hairs on their hairs, and so on down to the molecular level.
Just as human thumbs originally evolved for climbing and then got used for holding things in our hands could the van der waals forces that geckos use for climbing be used for holding objects in the hands of descendants of geckos?