It’s hard to say how smart or stupid an animal is, because animals may show their intelligence in ways that we don’t recognize.
But if the size of an animal’s brain in relation to the size of its body is any sign of intelligence, then the stupidest animal that ever lived was probably the dinosaur called stegosaurus. This huge reptile weighed some 13,000 pounds, yet had a brain that weighed only about 21/2 ounces!
A sperm whale 50 feet long would have a brain weighing about 20 pounds, while an adult elephant’s brain weighs about 10 pounds. A gorilla’s brain weighs about 20 ounces, and an adult person’s brain usually weighs around 3 pounds.
Your brain probably weighs more than 15 times as much as the brain of the huge stegosaurus.