Originally Posted by Arkie
I would argue that we have too much intelligence for our own good.
Vonnegut wrote a book about that called Galapagos
where man eventually evolves beyond his "too big brain" because it's causing him so many problems. Here's a synopsis of part of it from Wiki:
Galápagos is the story of a small band of mismatched humans who are shipwrecked on the fictional island of Santa Rosalia in the Galápagos Islands after a global financial crisis cripples the world's economy. Shortly thereafter, a disease renders all humans on Earth infertile, with the exception of the people on Santa Rosalia, making them the last specimens of humankind. Over the next million years, their descendants, the only fertile humans left on the planet, eventually evolve into a furry species resembling seals: though possibly still able to walk upright (it is not explicitly mentioned, but it is stated that they occasionally catch land animals), they have a snout with teeth adapted for catching fish, a streamlined skull and flipper-like hands with rudimentary fingers (described as "nubbins").
Humans are a strange lot. We have the intelligence to put rovers on Mars and yet the lizard and primate parts of our brains are still fully operational.