Why Isn't Your Brain In Your Foot?

In Psalm 139:14, the writer praises God by noting the design in the human body. "I am fearfully and wonderfully made," the writer says as he goes on to praise God's wisdom in all He produces. I once had a student who argued against the existence of God by noting all the injuries and problems people have because their heads are located five or six feet up in the air. "If God designed us, why isn't your brain in your foot?" he asked. "Then there would be a much lower risk of injury and it would be much easier to protect the brain."

The answer to this question comes out of the area of physics that deals with fluids. We all know that, when you dive deep into a lake, the pressure gets larger the deeper you go. In fact, the pressure increases in fresh water at the rate of 62.4 pounds per square foot for each one foot in depth you go--so 10 feet down in a lake, the pressure is 624 pounds per square foot larger than at the surface. This is also true of blood.

At the very top of a six foot tall person's head, the pressure is at a minimum. In that person's feet, the pressure of the blood is nearly 400 pounds per square foot higher. For this reason, it is much more likely that a blood vessel may break in your foot than it is in your head. As a person gets older, it is sometimes possible to see places where blood vessels have broken in ankles or feet. This may cause some pain and may produce some aesthetic problems, but it is not life threatening. What would happen, however, if the rupturing blood vessels were in the person's brain? The reason your brain is not in your foot is very obvious when you look at the fluid pressures and other dynamics involved.

Not only is the positioning of organs carefully designed to conform to the physics of fluids, but the system as a whole works because of it. In order to get enough blood to the brain to allow it to work, a law of physics called Pascal's law is used. Pascal's law says "pressure exerted on a fluid is distributed uniformly throughout the fluid." When the heart puts pressure on the blood, that pressure is distributed uniformly throughout the blood. This means the brain gets enough blood to function while the lower part of the body gets blood that has additional pressure on it by the blood column's height being added to the heart's function.

When medical scientists look at each organ in the body, they find that every part of the body maximizes the use of the physical forces made available to it. We are fearfully and wonderfully made, with a complexity that still challenges the best scientific minds among us.

Back to Contents Does God Exist?, March/April 1996