A bigger brain does not mean bigger thoughts. In fact, human brains were larger back when we were living in caves, but our bodies were also larger then. As we evolved, more of the space in our brains became used for complex processes such as language, thinking, and memory.
A 1999 study of Einstein’s brain, based on photographs taken of it after he died in 1955, showed that the parietal lobes, which are linked to math ability, appeared 15% wider than normal. But the size of his brain was a little smaller than average.
We may be the smartest creatures on the planet, but others have bigger brains. Larger brains are needed partly to control larger muscles. A sperm whale's brain weighs about 17 pounds and an elephant's weighs a little more than 10 pounds. An owl's brain weighs 0.005 pounds and a bullfrog's about one-tenth of that.
