There’s an interesting item in today’s Science Daily: a paper by University of Wyoming researcher Qin Zhu et al., suggests that the human size-weight illusion — which makes us think, if holding two objects of equal weight, that the larger one actually weighs less — is an evolved adaptation that helped us find objects of optimal size for throwing long distances. (Being able to throw well was vital to our success as hunters, so anything that helped would have been strongly selected for.)
What the article doesn’t explain is why this illusion would have helped us find objects good for throwing far. I assume it has something to do with the fact that air resistance is proportional to surface area — so of two differently sized objects with the same weight, the smaller one will have less surface area, and therefore will be less subject to drag as it flies through the air.
The article is here.