The survival value of a brain

Why did Nature give us more brains than is absolutely necessary for our survival? All She had to do was give us enough brains to be able to invent a few stone tools to make up for not giving us claws. That would have been enough to ensure our survival. What makes it more amazing is that Nature generally is very stingy with her gifts. Chimps have just enough brains to survive and procreate. On a good day, the deer can only run fast enough to out run the tiger. So why indulge humans?
A chap named Snell proposed a standard called encephalization quotient (EQ) to compare the brain to body weight ratios among various species. I found the following chart showing the EQ for a few mamals:

Man	7.44
Dolphin	5.31
Chimpanzee	2.09
Dog	1.17ut
Horse	0.86

It basically means that man's brain to body weight ratio is 7.44 times the average ratio for mamals. This really is over kill. 3 would have been sufficient. Look at the state Nature is in today. There is not a single part of her that is not fighting for survival today. And it is all due to the "extra" few ounces of brain matter she granted Man all those milenia ago. The first things man discovered that were more than just survival tools were fire and wheel. That was around 40,000 years ago. Since that day, Man has not done a single thing which has not upset Nature's equations in some way. He has made a mess of whatever he has touched. He is the only species to have single handedly brought the threat of total extinction upon himself. And not just himself, but all of Nature. None of this would have happened if Nature had stuck to her policy of giving just enough resources to enable a species to survive. That one mistake has effectively sealed her fate.

I found a nice article called What is intelligence, anyway? Its discusses the definition of intelligence and explores the relationship between brain and intelligence. The Wikipedia entry for human evolution is here.