Editor’s note: Physicians have a special place among the thinkers who have elaborated the argument for intelligent design. Perhaps that’s because, more than evolutionary biologists, they are familiar with the challenges of maintaining a functioning complex system, the human body. With that in mind, Evolution News & Views is delighted to present this series, “The Designed Body.” For the complete series, see here. Dr. Glicksman practices palliative medicine for a hospice organization.

Due to the laws of nature, the body must have enough energy for its trillions of cells to work properly. The body won’t function very well if its cells don’t have enough oxygen (O₂).

Evolutionary biologists claim that the organs described so far in this series, and the systems that control them, must have come about by chance and the laws of nature alone. But their theory seems to account only for how life looks and not how it actually works to stay alive under the laws of nature. Experience teaches that real numbers have real consequences when it comes to life and death.

Based on what we know about how the body actually works, our earliest ancestors had to be able to provide at least 3,500 mL/min of O₂, mainly to their muscles and heart, to be able to run fast enough and fight hard enough to win the battle for survival. That would have required their lungs to have a rapid enough airflow, a large enough volume, and an efficient enough gas exchange to bring in enough O₂. It would also have required that they have enough iron to make enough hemoglobin to be able to carry enough O₂ in the blood. And finally, their cardiac output (CO) needed to be at least 25 L/min to sustain the kind of activity levels needed to hunt rather than be hunted.

As I’ve noted in previous articles, lung function, hemoglobin production, and cardiac output are controlled by irreducibly complex systems, each consisting of sensors, integrators, and effectors that must also inherently know what is needed for survival. I call this natural survival capacity, because the systems involved must naturally have the capacity to keep a specific chemical or physical parameter within a certain range to allow for survival. We have looked at what happens to the body when its lung function and hemoglobin production do not measure up to what is needed. Now we will start to look at what happens when cardiac function is not up to snuff.

At rest the average male needs about 250 mL/min of O₂ to keep all of his organs working properly, and any increase in activity requires more. Walking slowly requires 500 mL/min of O₂; walking quickly, 1,000 mL/min; moderate jogging, 2,000 mL/min; and fast running, 3,500 mL/min of O₂. Since we know that the CO has to be at least 25 L/min for maximum activity, we can figure out what the minimum CO levels would have to be for lesser activity levels. We can do this by multiplying 25 L/min by the ratio of the lower and maximum O₂ consumption. So to jog at a moderate pace, the minimum CO would have to be 25 x 2,000/3500 = 14.3 L/min. To walk quickly would take at least a CO of 7.2 L/min, to walk slowly a CO of 3.6 L/min, and to stay at rest would need a CO of 1.8 L/min.

It is important to note here that these are real numbers that reflect real life and the laws of nature. No matter what evolutionary biologists say about how matter must have organized itself into the complex systems we know are needed for life, medical science tells you that if you don’t have a CO of 7.2 L/min, you can’t walk very quickly, if you don’t have a CO of 3.6 L/min, it would be very difficult for you to walk even slowly, and if you don’t have a CO of at least 1.8 L/min, you are probably dead. Certain parameters of cardiac function had to be met for our ancestors to survive within the laws of nature, and no expenditure of imaginary effort can deny this fact.

When real numbers lead to chronic debility with respect to the lungs, they usually involve problems with ventilation and/or gas exchange. But when dealing with chronic debility and the heart, we usually encounter four different problems. Each condition, individually, is capable of causing significant debility but, in real life, they often occur in combination. Just as adding a gas exchange problem to a ventilation problem can more quickly lead to worsening debility from pulmonary dysfunction, so too a combination of more than one of these cardiac conditions can quickly lead to significant weakness and a limited ability to be active and manage independently.

The commonest heart condition in developed countries, and what most people think of when they hear someone has heart trouble, is coronary artery disease. Even though the heart pumps blood throughout the body, it must also supply adequate blood flow to itself so it can do its job. As the blood flows out of the left ventricle through the aortic valve, the coronary arteries turn back over the surface of the heart. The heart is the hardest working muscle in the body and when its blood supply is compromised this can lead to significant debility and even death.

Another common cardiac condition is valvular heart disease. The “V” shaped one-way valves between the atria and the ventricles and the ventricles and their outflow tracts are structured in a way that allows them, when open, to facilitate the forward movement of blood, and when closed, to prevent blood from going backward. The efficiency of cardiac function is dependent not only on adequate coronary blood flow, but also on properly working valves. A valve can’t be too tight, slowing forward blood flow, or too lax, allowing backward flow.

When the heart cannot meet the metabolic needs of the body it is said to be in heart failure. This third common cardiac condition can involve either the left or the right side of the heart alone, or both at the same time. In addition, left ventricular failure can be systolic, where reduced muscle contractility leads to weaker pumping action, and/or diastolic, where increased muscle stiffness reduces relaxation and the filling of the ventricle with blood. Both coronary artery and valvular heart disease are common causes of heart failure.

The fourth common cardiac condition is the cardiac arrhythmias. It is the sino-atrial node, the natural pacemaker in the right atrium that dominates the other excitable cells in the heart. It controls the heart rate and starts coordinated atrial contraction and the conducting system makes sure that coordinated ventricular contraction takes place soon afterward. Any disruption or short-circuiting of this signal formation, impulse conduction or coordinated muscle contraction can lead to significant debility and even death. All three of the conditions mentioned above, and other disorders, can predispose the heart to cardiac arrhythmias.

When real numbers lead to functional problems of the heart, these are usually the four main conditions that contribute to the situation. In the next few articles we will take a closer look at each of them.

Image: � Sergey Nivens / Dollar Photo Club.