Regina Wilshire is absolutely right.
Would you willingly sit your child down, offer him/her a bowl filled with 1/2 cup of sugar and a spoon to dig in?
It's like I often say when people try to insist to me how great fruit juices are: would you sit down and eat a dozen or two dozen oranges in a single sitting? Think your body was designed to do that?
And sure, we can handle it (infrequently). I'm quite certain that primitive man gorged on sweet stuff opportunistically, like on honey when he came across it, or some sweet fruits (though primitive fruits were largely fibrous and tart — not like today's selectively bread stuff). More likely, they gorged on berries when they could, seasonally and very intermittently — not a daily thing.