While the human brain has grown larger over the past two million years, since the past 20,000 years it has become smaller. However, although the human brain comprises only 2 percent of the body's mass, it uses 20 percent of person's energy.
Another interesting fun fact is that the cerebral cortex makes up 85 percent of the human brain. Although the cerebellum comprises only 10 percent of the brain, it has half of the neurons. Also, there are 186 more neurons in the left hemisphere of the brain than in the right hemisphere.
Amazingly, during early pregnancy, the brain grows at the rate of 250,000 neurons a minute. After age 30, the brain shrinks a quarter of a percent each year, yet 30 percent of 80-year-olds perform as well as young people on cognitive tests.
A single human brain generates more electrical impulses in a day than all the telephone lines in the world. The average person has around 70,000 thoughts on any given day, and these thoughts travel at a minimum of 260 mph. With its blood supply cut off, the brain loses unconsciousness in 10 seconds, and without oxygen, its cells begin to die in four to six minutes.