Dolphins really aren't that intelligent. Their tool use is on par with a human infant. Their brain may be physically larger, but this is held back by numerous factors:
- The average dolphin is considerably larger than a human. Larger body size = more brain power dedicated to locomotion and less to other things.
- The dolphin's brain has thicker insulation, which is needed for ocean survival yet has no function for brain activity, when this is removed, the dolphin's brain is actually smaller than the human brain (when the insulation is removed from the human brain as well)
- The dolphin's brain has a smaller surface area than a human's, which is the primary function of intelligence. This is due to fewer "wrinkles" as well as the smaller volume.
The effect of having to dedicate more brain function to locomotion with a smaller brain makes the dolphin objectively less capable intellectually than humans. Yes, they're bright creatures, yet not some kind of super-animal. The human has the highest cognitive function of any animal species on the planet and even our least intelligent members are more capable than the upper echelon the dolphin intelligence.
That and tool use has been known for a very long time among the Australian bottlenose community, making me wonder why the article was written in 2009.