Many science-fiction movies feature aliens with slight bodies and enormous brains. Such portrayals support the theme that an extraterrestrial ecosystem might permit the existence of a superintellect race that could develop the technology for interstellar space travel. These creatures may look impressive on screen, but this theme violates the laws of physics in two ways.
First, as demonstrated in the Reasons To Believe book Lights in the Sky and Little Green Men,1 no animal bigger than an inch can physically survive an interstellar journey in any conceivable spacecraft that is smaller than a planet or a large moon. Second, it is not possible for a land animal to possess a brain-to-total-body-mass ratio significantly larger than that manifested in humans.
A new research study not only provides additional evidence that the human brain is at the maximum size possible, but also shows that the human brain is designed for maximum intelligence performance. Before this particular study emerged, physiologists had determined that the human brain receives about a third of the body's blood flow and that its functions account for about a fifth of the body's energy consumption. This incredibly high expenditure of bodily resources sustains an organ that, even for a slender adult, comprises no more than two percent of body mass. Yet this two percent ranks the highest among all animals.
Huge blood flow provides the necessary energy to the brain and keeps it sufficiently cool. If not for the human body's bipedal structure, slim build, lack of excess hair, efficient sweating capacity, and large blood flow, the human brain would cook and lose much of its mental abilities. Considering these requirements plus the challenge of passing a baby's head through the birth canal, it is not physiologically possible for the human brain-to-body-mass ratio to be any larger than it is.
The new study directly measured, for the first time, the energy cost of the brain's information processing systems.2 These systems involve the rapid flow of electrical charges across neuronal membranes. Sodium, potassium, and calcium ions carry the charges. In turn, the ion flow in the brain is carried by electrochemical gradients maintained by ionic pumps.
Through simulations of brain function, previous energy budget calculations determined that the ionic pumps ran at about 25 percent efficiency, which is equivalent to the best-designed human machines. In the new study three German neurophysiologists used functional brain imaging measurements on the rat hippocampus to determine the relative kinetic properties of the sodium and potassium ion pumps. Their measurements showed that the energy utilization was three times less than what the earlier energy budget calculations had indicated. An "energy demand per action potential of only 1.3 times the theoretical minimum"3 implies that the ion pumps are perfectly optimized.
Where did this optimization come from? The German neurophysiologists credit "evolution." They conclude that their results are "in line with considerations that in evolution the economy of neural processes tends to be optimized."4 A more accurate statement is that the economy of neural processes appears to be optimized in all species of birds and mammals. However, they lack any evidence that the economy of neural processes evolved from suboptimal to optimal. Given this evidence deficiency, it is more reasonable to conclude that a supernatural Creator intentionally designed neural processes to be optimally efficient and that he repeated this optimal design throughout all species of birds and mammals.
The study by the German neurophysiologists yields additional support for the design of the human brain for the best possible intellectual prowess. The human brain already is receiving the maximum possible supply of energy that is physiologically possible. The researchers' discovery establishes that the energy supply is being exploited in the most efficient manner possible for information processing.
In a different context, the human brain reveals additional evidence that it has been designed for maximum intellectual performance. In nonhuman mammals, significant fractions of the brain mass are devoted to supporting muscles and the five senses. (About forty percent of a dog's brain supports its sense of smell.) But the human brain is partitioned to deliver the maximum possible resources to intellectual activities. It looks like the Creator designed the internal structure of the human brain in a manner seen in no other species, so that humanity would have the greatest possible intellectual capabilities.