ScienceDaily (Jan. 24, 2011) — Can't help molding some snow into a ball and hurling it or tossing a stone as far into a lake as you can? New research from Indiana University and the University of Wyoming shows how humans, unlike any other species on Earth, readily learn to throw long distances.
The study, appearing online Jan. 14 in the journal Evolution and Human Behavior, suggests that the well-established size-weight illusion, where a person who is holding two objects of equal weight will consider the larger object to be much lighter, is more than just curious or interesting, but a necessary precursor to humans' ability to learn to throw -- and to throw far.
Another way of stating the size-weight illusion is that for someone to perceive that two objects -- one larger than the other -- weigh the same, the larger object must weigh significantly more than the smaller object. Their study findings show that skilled throwers use this illusion of 'equal felt' heaviness to select objects that they are able to throw to the farthest, maximum distance. This, says Bingham, suggests the phenomenon is not actually an illusion but instead a "highly useful and accurate perception."
Neanderthals, which co-existed with Homo sapiens long ago, lacked the more developed cerebellum and posterior parietal cortex.
"These brain structures have recently been found to distinguish Homo sapiens from Neanderthals," Bingham said. "It is possible that this is what enabled us to beat out Neanderthals, who otherwise had the larger brains."
I suppose wind resistance is the reason we evolved to have this illusion.
Being useful doesn't mean it's not an illusion.