> Thus if intelligence is a factor at all in survival (and it seems like it should be) your ancestors may not have had a choice but to select for intelligent.

And this explains the large collection of (in our understanding) not-terribly-intelligent creatures on the planet how?

Not trying to be snarky, just pointing out that intelligence is just one of many paths, and it's very hard to have strong conclusion about how something so rare fares in evolution, and if the tend will maximize or if it pays off to be "just a little" intelligent, just like it pays to be "just a little" able to swim.