Kort Explores conundrums of the human condition

Heat dissipation is a critical engineering constraint in all computing devices - both in solid state electronic "hardware" and organic "wet-ware" like the human brain. Computers and brains have only been able to increase in complexity and capability by concurrently evolving ever more sophisticated cooling systems.

The total heat generated by computers has dropped substantially over the years, but the heat density in CPU (Central Processing Unit) chips has increased. While their physical area has decreased exponentially, the amount of heat each square inch generates has soared. Some modern CPU chips generate more heat per square inch than a stove top, and it doesn't take long to reach the melting points of their component materials if that heat isn't constantly drawn off. Distressingly expensive computers have destroyed themselves in a cascading chain of catastrophic failures triggered by the demise of the machine's cheap cooling fan.

The 2 primary means of increasing the power of hardware computers have been to increase circuit density and cycle speed. Both approaches increase the heat density of the resulting system - more heat in a smaller area, which complicates the cooling problem. The technical solutions to heat dissipation employed in the evolution of human engineered computers and naturally evolving organic brains are remarkably similar - at least in principle. As circuit density and computing power have increased, computer manufacturers have employed heat sinks, heat pipes, cooling fans, and in the case of supercomputers, immersing the circuits in liquid coolant to keep the machines from melting themselves down.

The brain is the most thermally sensitive organ in the body. The human brain will fail/die if subjected to a 5 Degree C increase over its normal operating temperature. And while it is the least tolerant of excess heat, the brain consumes more energy and therefore needs to reject more waste heat per unit of volume than any other part of the body.

The basic nature of an animal can in large part be determined by analyzing which parts of its brain it uses most. Those parts of the brain that are most useful to the animal - and are therefore most active - require the greatest energy supply and cooling capacity. The nature of the brain's blood supply and cooling system can in large measure define the nature of the animal.

Most of the rest of the systems in the body can function - or at least survive - a far wider range of operating temperatures than the brain. Most warm blooded animals that live exposed to the elements are able to control the operating temperatures of their brains separately from that of their bodies. They allow the operating temperature of their bodily systems to vary over a much wider range in order to minimize the heating and cooling demands on their metabolism and behavior patterns. However, even these animals must maintain the operating temperature of their brains to a much finer degree. Humans are relatively intolerant of temperature differences between brain and body, and can only survive a relatively narrow range of temperatures without artificial accommodations like clothing and housing.

Overheating is the primary concern of the temperature control systems linked to organic brains. Excess heat loss to a cold environment can be mitigated by fur, insulation, mass, etc. The danger of overheating is encountered more frequently and is more lethal than being too cold. Since recovery from a fatal overheat is not possible, the maximum brain activity possible in a given environment is to a large degree determined by the brain's cooling system capacity. The better the cooling system, the more complex, and theoretically more intelligent, the brain it will support.

Since the brain is a wet-ware device employing various fluids in its operation, using those fluids in some way to convey heat out of the brain figures in most organic cooling systems. However, there are large variations in the complexity and effectiveness of the approaches taken by various species.

The long snouts and large nasal cavities of many air breathing animals are used to selectively cool their brains. Heat flows out of their brains in fluids that are cooled by contact with their nasal membranes. The excess heat from their brains is transferred across the membranes to the air being pumped through by their lungs, providing a kind of internal forced air cooling system.

However, there are functional limits to the size and therefore cooling capacity of internal forced air systems. A true wolfman would not be viable as the proposed larger brain would burn itself out linked to the limited cooling capacity of the wolf's internal forced air system. A snout large enough to cool a human type brain would severely unbalance a man/wolf size being, pretty much eliminating the creature's potential as a terrifying monster. Its victims would have to be extraordinarily cooperative...

As brain size increased through evolution, larger brains generated more heat that had to be dissipated. Recent fossil finds indicate that the evolution of the brain's auxiliary cooling system preceded the evolution of the brain itself.

We still have our original primitive core brain and cooling system. Evolution didn't throw much out when it came to the human brain - it just kept adding new layers. "Cool" blood entering the brain at the base keeps most of the core areas cooled under most circumstances. However, as the main supply of blood flows outward through the brain, it has already picked up heat from the core and is less effective in controlling the temperature of the outer layers. High level cognitive functions exist in the outer most layers, and are therefore the first to be affected when heat distress sets in. People usually go "crazy from the heat" long before the older more primitive core systems that control their hearts and lungs overheat and shut down.

Humanity has evolved a unique auxiliary cooling system that employs the skin as a radiator and blood as coolant to help deal with the overheating problems that accompany complex brains. Human skulls are perforated with thousands of openings for emissary veins. These emissary veins are unusual in that they allow bidirectional blood flow. The number of these veins has grown as brain size has grown, increasing the capacity of the brain's auxiliary liquid cooling system as the amount of waste heat being generated increased.

Under normal conditions, blood drains out of the brain through the emissary veins. When the brain experiences heat distress, blood flow in the emissary veins reverses, drawing blood cooled by the skin "radiator" into the overheated brain to absorb the excess heat. The effectiveness of our skin pre-cooler is further enhanced by the evaporation of sweat from its outer surface.

So, it appears that there really is something to "keeping a cool head". As unlikely as it might seem, we owe our intelligence in large measure to the holes in our heads. The more holes we evolved, the smarter we became. Remember this the next time someone says "I need that like I need another hole in my head..."

Note: The number and disposition of cranial perforations is best left up to evolution. This article should not be interpreted as advocating the creation of additional "brain cooling" cranial perforations in living beings. Most experiments in "augmented brain cooling" have proven deleterious to the subject...