Nanotech and Life Extensions

Introduction

This chapter is not really about life extension. Instead, its focus is on health extension: keeping the body in a state of good health. This is a simpler topic, because we can ignore several philosophical questions. However, as the chapter unfolds, it will become clear that life extension is a natural consequence of health extension. As diseases are cured, causes of death will be avoided; as people make use of technology to improve their health, they will find themselves living longer--perhaps much longer.

A few thousand years ago, people lived about thirty years. From their point of view, we have already extended our lives to an amazing degree. However, from where we stand today, we can see that we still have a long way to go. Some people still die in their 40's from cancer, heart attack, stroke, and infections. This is tragic, and frustrating. Today's medicine is only somewhat able to deal with these and other conditions--and it has barely started to attack the problem of aging. But we can see light at the end of the tunnel.

Fifty years from now, what causes of death will be preventable? That depends largely on the technology we will have available, so let's start by projecting some technology trends. Gene sequencing and identification will be as easy as a blood sugar test. Medical devices such as artificial hearts and insulin pumps will be implantable and well-integrated with the body's natural demands. Surgical instruments will be more delicate and less destructive; what today is "major surgery" will be done with an office visit. Computers will be millions of times faster than today's machines. Last but not least, we will probably have the ability to build strong, useful, complex machines out of individual atoms and molecules. This is called "nanotechnology" or simply "nanotech", and it will make us healthier in several important ways.

Can we expect technology to solve all our medical problems? This chapter will answer that question by examining what nanotech can do for medicine. Nanotech is a huge topic, and medicine is even bigger, so this chapter can give only a sketchy overview. On the nanotech side, we will focus on robot-like machines with precise molecular parts; on the medicine side, we will limit ourselves to a mechanical view of medicine that mostly ignores the complexity that arises from all the body's systems working together. And I'll be remarkably unambitious (by future standards) in defining "good health": Good health is when the body is able to support typical activities without significant discomfort. (Optimum health is a matter of personal preference, and the chapter is long enough without getting into all the ways people could improve their bodies.) Even with these restrictions, it will become clear that nanotech can solve most or all of the medical problems that might keep us from being in good health, thus allowing us to remain in a state of good health for many decades or even centuries.

Background

Biology and Chaos

In order to be in good health, every system in the body (including the systems we haven't discovered yet) must be functioning well. Furthermore, the states of each system must be in sync with each other so that they will keep functioning well for a reasonable period of time. If the lungs are working faster than the muscles, the blood will gain too much oxygen and lose too much carbon dioxide, which will soon throw several systems off balance. But if all your systems are working well, and working together well, then your health will be good.

An automobile can be analyzed piece by piece. If the battery is dead, the headlights won't work; the burning gasoline pushes on the piston, which makes the wheels turn; and so on. A biological organism is not so simple. Frequently there is no clear boundary between the parts--one part may have several functions, and the whole system is in constant flux. A simple mechanical analysis will miss subtleties of operation. In fact, there is a whole new branch of mathematics called chaos that had to be invented to deal with systems like this.

You may have heard of the "butterfly effect"--a butterfly flapping its wings in China may create an air current that grows into a hurricane months later. A chaotic system, such as the weather or the human body, is inherently unpredictable: no matter how precisely you know its starting state, you can't tell what it will do in the future. (As we'll see later, most butterflies do not cause hurricanes--the point is that a single butterfly can sometimes make a big difference.) In fact, the body seems to depend on chaos. Normally the timing of the heartbeat is chaotic; if it ever becomes more regular, the person is about to have a heart attack. (References are at the end of this article.)

Suppose you wanted to study the body's response to exercise. You could look at the effect of blood oxygen level on breathing rate by making a graph with oxygen level on one axis and breathing rate on the other. Measure each quantity at one-minute intervals, plot the resulting points on the graph, and draw a line between successive points. If the relationship were perfectly simple, the graph would show a diagonal line: breathing rate would increase when oxygen level went down, and decrease as oxygen level recovered. In fact, because breathing affects oxygen level with some delay, the graph will show a cycle: first the oxygen decreases, then breathing increases, then oxygen increases, then breathing decreases, and around and around it goes. On the graph, this cycle would appear as an oval. Other factors would be deforming the shape. Over time, you would notice that the tracing crossed itself repeatedly. And you'd see something else: there would be more than one oval on the graph, representing states of waking, sleep, and so on, and the lines running from one oval to another would themselves be interestingly complex. If you did the experiment for years, you would find that all the lines stayed within a certain area of the graph: the breathing rate would never be above, say, 120 breaths per minute or below one breath every three minutes.

Now consider all the vast array of bodily mechanisms and substances. You could make a 3-D graph by adding insulin to your list of things to measure. But there are hundreds of hormones in the body, as well as other chemicals, temperature (core and extremity), bacterial counts, and physical conditions including scarring and posture. You would have to make a 300-D graph! If