© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

16.2.2  The Limits of Immortality

Brain cells do not reproduce and cannot replace themselves once destroyed. Each human possesses ten billion irreplaceable neurons; when some are lost due to concussion, consumption of alcohol or tobacco, or from natural causes, our brains are permanently diminished.

Dr. Harold Brody of the State University of New York at Buffalo attempted to measure the rate of natural attrition of brain cells. While losses range from none at all to very many in various parts of the organ, the approximate brainwide average runs about 100,000 neurons lost per day. At this rate, Brody calculates, the organ should entirely decay away in a period of about 250-350 years.²⁶⁴⁸ Whether cell loss would actually continue to the vanishing point or would taper off asymptotically is unknown at present.

There are at least three solutions to the so-called "brain barrier" problem. First, genetic engineering could permit each individual to start out with a larger brain. If the ETs have 100 billion neurons -- ten times more than we -- and the same neural attrition rate, senility might not set in for thousands, instead of hundreds, of years. The full millenium of Stage 3 aging would then become available to the aliens.

A second solution is to cause brain cells to regenerate and reproduce them selves as others died. If neuron division could be exactly balanced against cell losses, the brain would remain the same size and theoretically could go on forever. This again will only be found among extraterrestrial races capable of advanced bioneering, since there is no natural selective value in developing complex brain regeneration mechanisms which aid survival only if the organism manages to pass the primary and secondary self-destruct systems of the body. What if aliens did have divisible brain cells? In his book The Immortality Factor, Osborn Segerberg, Jr. writes:

[Brain cells] store our memories, experiences, knowledge and learning as well as operate voluntary and autonomic nervous systems. New brain and nerve cells presumably would "forget" what their predecessors knew. If the [being] survived the neurological havoc, he might not be able to retain his identity. He would forever be turning into someone else.⁶⁹

Or, as another writer puts it: "That would be the fun of attaining great longevity if the lucky winner couldn't remember what had gone before?"²¹³⁷

Of course, the counterargument goes like this: We know we lose 100,000 neurons every day. If this causes personality change from day to day, we certainly do not notice it. Why should the random addition of 100,000 neurons every day wreak any more cerebral havoc than their random subtraction? Brain regeneration may be quite possible, after all.

A third solution to the brain barrier problem is simply to prevent neural cells from dying at all, or at least to significantly slow the rate of attrition. We don’t know how to do this yet -- perhaps more robust and wear-resistant cells could be designed -- but alien sentients elsewhere may have already found the answer.

Assuming ETs and earthlings manage to lick the brain barrier problem, then exactly what are the limits to immortality? Saving the organ of sentience doesn’t get us out of the woods yet, because there is still the problem of accidental death associated with Stage 3. Individuals may be hit by a truck, slip in the bathtub, be shot in battle, or die in a plane crash.

Still, the lifespan in Stage 3 may be an order of magnitude greater than in Stage 1 (where humans are now). For example, the death rate in the United States in 1973 was 942 deaths per 100,000 people. The maximum lifespan attainable was about 100 years. If all purely medical deaths were eliminated, leaving only suicide, homicide and accidental causes (fire, drowning, lightning, and other sudden traumas), the death rate would have dropped to 78 cases per 100,000 people. This works out to a maximum attainable lifespan of nearly 1300 years, as shown in Figure 16.1.

Is this the upper limit, then? If accidental causes of death can be eliminated we can get more. But how could this be done? One recent science fiction story proposes the development of a sense of precognition or foreknowledge to enable the creature to anticipate accidents in the near future and avoid them.²⁶⁵⁰ This accomplished, there should be no further real limits to immortality, save boredom or a brain jammed to capacity with memories like a well-worn palimpsest. Death would occur only as a matter of affirmative, intelligent choice.

Last updated on 6 December 2008