Not much imagination is needed to foresee the effectiveness of artificial organisms as scavengers. A suitable microorganism could convert the dangerous organic mercury in our rivers and lakes to a harmless insoluble solid. We could make good use of an organism with a consuming appetite for polyvinyl chloride and similar plastic materials which now litter beaches all over the Earth. Conceivably we may produce an animal specifically designed for chewing up dead automobiles. But one may hope that the automobile in its present form will become extinct before it needs to be incorporated into an artificial food chain. A more serious and permanent role for scavenging organisms is the removal of trace quantities of radioactivity from the environment. The three most hazardous radioactive elements produced in fission reactors are strontium, caesium, and plutonium. These elements have long half-lives and will inevitably be released in small quantities so long as mankind uses nuclear fission as an energy source. The long-term hazard of nuclear energy would be notably reduced if we had organisms designed to gobble up these three elements from water or soil and to convert them into indigestible form. Fortunately, none of these three elements is essential to our body chemistry, and it therefore does us no harm if they are made indigestible.
I have described the two first steps of biological engineering. The first will transform our industry and the second will transform our earthbound ecology. It is now time to describe the third step, which is the colonization of space. Biological engineering is the essential tool which will make Bernal’s dream of the expansion of mankind in space a practical possibility.
First I have to clear away a few popular misconceptions about space as a habitat. It is generally considered that planets are important. Except for Earth, they are not. Mars is waterless, and the others are for various reasons basically inhospitable to man. It is generally considered that beyond the sun’s family of planets there is absolute emptiness extending for light-years until you come to another star. In fact it is likely that the space around the solar system is populated by huge numbers of comets, small worlds a few miles in diameter, rich in water and the other chemicals essential to life. We see one of these comets only when it happens to suffer a random perturbation of its orbit which sends it plunging close to the sun. It seems that roughly one comet per year is captured into the region near the sun where it eventually evaporates and disintegrates. If we assume that the supply of distant comets is sufficient to sustain this process over the billions of years that the solar system has existed, then the total population of comets loosely attached to the sun must be numbered in the billions. The combined surface area of these comets is then a thousand or ten thousand times that of Earth. I conclude from these facts that comets, not planets, are the major potential habitat of life in space. If it were true that other stars have as many comets as the sun, it then would follow that comets pervade our entire galaxy. We have no evidence either supporting or contradicting this hypothesis. If true, it implies that our galaxy is a much friendlier place for interstellar travelers than it is popularly supposed to be. The average distance between habitable oases in the desert of space is not measured in light-years, but is of the order of a light-day or less.
I propose then an optimistic view of the galaxy as an abode of life. Countless millions of comets are out there, amply supplied with water, carbon, and nitrogen, the basic constituents of living cells. We see when they fall close to the sun that they contain all the common elements necessary to our existence. They lack only two essential requirements for human settlement, namely warmth and air. And now biological engineering will come to our rescue. We shall learn to grow trees on comets.
To make a tree grow in airless space by the light of a distant sun is basically a problem of redesigning the skin of its leaves. In every organism the skin is the crucial part which must be most delicately tailored to the demands of the environment. The skin of a leaf in space must satisfy four requirements. It must be opaque to far-ultraviolet radiation to protect the vital tissues from radiation damage. It must be impervious to water. It must transmit visible light to the organs of photosynthesis. It must have extremely low emissivity for far-infrared radiation, so that it can limit loss of heat and keep itself from freezing. A tree whose leaves possess such a skin should be able to take root and flourish upon any comet as near to the sun as the orbits of Jupiter and Saturn. Further out than Saturn the sunlight is too feeble to keep a simple leaf warm, but trees can grow at far greater distances if they provide themselves with compound leaves. A compound leaf would consist of a photosynthetic part which is able to keep itself warm, together with a concave mirror part which itself remains cold but focuses concentrated sunlight upon the photosynthetic part. It should be possible to program the genetic instructions of a tree to produce such leaves and orient them correctly toward the sun. Many existing plants possess structures more complicated than this.
Once leaves can be made to function in space, the remaining parts of a tree—trunk, branches, and roots—do not present any great problems. The branches must not freeze, and therefore the bark must be a superior heat insulator. The roots will penetrate and gradually melt the frozen interior of the comet, and the tree will build its substance from the materials which the roots find there. The oxygen which the leaves manufacture must not be exhaled into space. Instead it will be transported down to the roots and released into the regions where humans will live and take their ease among the tree trunks. One question still remains. How high can a tree on a comet grow? The answer is surprising. On any celestial body whose diameter is of the order of ten miles or less, the force of gravity is so weak that a tree can grow infinitely high. Ordinary wood is strong enough to lift its own weight to an arbitrary distance from the center of gravity. This means that from a comet of ten-mile diameter trees can grow out for hundreds of miles, collecting the energy of sunlight from an area thousands of times larger than the area of the comet itself. Seen from far away, the comet will look like a small potato sprouting an immense growth of stems and foliage. When humans come to live on the comets, they will find themselves returning to the arboreal existence of their ancestors.
We shall bring to the comets not only trees but a great variety of other flora and fauna to create for ourselves an environment as beautiful as ever existed on Earth. Perhaps we shall teach our plants to make seeds which will sail out across the ocean of space to propagate life upon comets still unvisited by humans. Perhaps we shall start a wave of life which will spread from comet to comet without end until we have have achieved the greening of the galaxy. That may be an end or a beginning, as Bernal said, but from here it is out of sight.
In parallel with our exploitation of biological engineering, we may achieve an equally profound industrial revolution by following the alternative route of self-reproducing machinery. Self-reproducing machines are devices which have the multiplying and self-organizing capabilities of living organisms but are built of metal and computers instead of protoplasm and brains. It was the mathematician John von Neumann who first demonstrated that self-reproducing machines are theoretically possible and sketched the logical principles underlying their construction. The basic components of a self-reproducing machine are precisely analogous to those of a living cell. The separation of function between genetic material (DNA) and enzymatic machinery (protein) in a cell corresponds exactly to the separation between software (computer programs) and hardware (machine tools) in a self-reproducing machine.
I assume that in the next century, partly imitating the processes of life and partly improving on them, we shall learn to build self-reproducing machines programmed to multiply, differentiate, and coordinate their activities as skillfully as the cells of a higher organism such as a bird. After we have constructed a single egg-machine and supplied it with the appropriate computer program, the egg and its progeny will grow into an industrial complex capable of performing economic tasks of arbitrary magnitude. It can build cities, plant gardens, construct electric power-generating facilities, launch spaces
hips, or raise chickens. The overall programs and their execution will remain always under human control.
The effects of such a powerful and versatile technology on human affairs are not easy to foresee. Used unwisely, it offers a rapid road to ecological disaster. Used wisely, it offers a rapid alleviation of all the purely economic difficulties of mankind. It offers to rich and poor nations alike a rate of growth of economic resources so rapid that economic constraints will no longer be dominant in determining how people are to live. In some sense this technology will constitute a permanent solution of mankind’s economic problems. Just as in the past, when economic problems cease to be pressing, we shall find no lack of fresh problems to take their place.
It may well happen that on Earth, for aesthetic or ecological reasons, the use of self-reproducing machines will be strictly limited and the methods of biological engineering will be used instead wherever this alternative is feasible. For example, self-reproducing machines could proliferate in the oceans and collect minerals for human use, but we might prefer to have the same job done more quietly by corals and oysters. If economic needs were no longer paramount, we could afford a certain loss of efficiency for the sake of a harmonious environment. Self-reproducing machines may therefore play on Earth a subdued and self-effacing role.
The true realm of self-reproducing machinery will be in those regions of the solar system that are inhospitable to humans. Machines built of iron, aluminum, and silicon have no need of water. They can flourish and proliferate on the moon or on Mars or among the asteroids, carrying out gigantic industrial projects at no risk to the Earth’s ecology. They will feed upon sunlight and rock, needing no other raw material for their construction. They will build in space the freely floating cities that Bernal imagined for human habitation. They will bring oceans of water from the satellites of the outer planets, where it is to be had in abundance, to the inner parts of the solar system where it is needed. Ultimately this water will make even the deserts of Mars bloom, and humans will walk there under the open sky breathing air like the air of Earth.
Taking a long view into the future, I foresee a division of the solar system into two domains. The inner domain, where sunlight is abundant and water scarce, will be the domain of great machines and governmental enterprises. Here self-reproducing machines will be obedient slaves, and people will be organized in giant bureaucracies. Outside and beyond the sunlit zone will be the outer domain, where water is abundant and sunlight scarce. In the outer domain lie the comets where trees and humans will live in smaller communities, isolated from one another by huge distances. Here humans will find once again the wilderness that they have lost on Earth. Groups of people will be free to live as they please, independent of governmental authorities. Outside and away from the sun, they will be able to wander forever on the open frontier that this planet no longer possesses.
I have described how we may deal with the World and the Flesh, and I have said nothing about how we may deal with the Devil. Bernal also had difficulties with the Devil. He admitted in the 1968 foreword to his book that the chapter on the Devil was the least satisfactory part of it. The Devil will always find new varieties of human folly to frustrate our too rational dreams.
Instead of pretending that I have an antidote to the Devil’s wiles, I end with a discussion of the human factors that most obviously stand in the way of our achieving the grand designs which I have been describing. When mankind is faced with an opportunity to embark on any great undertaking, there are always three human weaknesses that devilishly hamper our efforts. The first is an inability to define or agree upon our objectives. The second is an inability to raise sufficient funds. The third is the fear of a disastrous failure. All three factors have been conspicuously plaguing the United States space program in recent years. It is a remarkable testimony to the vitality of the program that these factors still have not succeeded in bringing it to a halt. When we stand before the far greater enterprises of biological technology and space colonization that lie in our future, the same three factors will certainly rise again to confuse and delay us.
I want now to demonstrate to you by a historical example how these human weaknesses may be overcome. I shall quote from William Bradford, one of the Pilgrim Fathers, who wrote a book, Of Plimoth Plantation, describing the history of the first English settlement in Massachusetts. Bradford was governor of the Plymouth colony for twenty-eight years. He began to write his history ten years after the settlement. His purpose in writing it was, as he said, “That their children may see with what difficulties their fathers wrestled in going through these things in their first beginnings. As also that some use may be made hereof in after times by others in such like weighty employments.” Bradford’s work remained unpublished for two hundred years, but he never doubted that he was writing for the ages.
Here is Bradford describing the problem of inability to agree upon objectives. The date is spring 1620, the same year in which the Pilgrims were to sail:
But as in all businesses the acting part is most difficult, especially where the work of many agents must concur, so was it found in this. For some of those that should have gone in England fell off and would not go; other merchants and friends that had offered to adventure their moneys withdrew and pretended many excuses; some disliking they went not to Guiana; others again would adventure nothing except they went to Virginia. Some again (and those that were most relied on) fell in utter dislike with Virginia and would do nothing if they went thither. In the midst of these distractions, they of Leyden who had put off their estates and laid out their moneys were brought into a great strait, fearing what issue these things would come to.
The next quotation deals with the perennial problem of funding. Here Bradford is quoting a letter written by Robert Cushman, the man responsible for buying provisions for the Pilgrims’ voyage. He writes from Dartmouth on August 17, 1620, desperately late in the year, months after the ships ought to have started:
And Mr. Martin, he said he never received no money on those conditions; he was not beholden to the merchants for a pin, they were bloodsuckers, and I know not what. Simple man, he indeed never made any conditions with the merchants, nor ever spake with them. But did all that money fly to Hampton, or was it his own? Who will go and lay out that money so rashly and lavishly as he did, and never know how he comes by it or on what conditions? Secondly, I told him of the alteration long ago and he was content, but now he domineers and said I had betrayed them into the hands of slaves; he is not beholden to them, he can set out two ships himself to a voyage. When, good man? He hath but fifty pounds in and if he should give up his accounts he would not have a penny left him, as I am persuaded. Friend, if ever we make a plantation, God works a miracle, especially considering how scant we shall be of victuals, and most of all ununited amongst ourselves and devoid of good tutors and regiment.
My last quotation describes the fear of disaster, as it appeared in the debate among the Pilgrims over their original decision to go to America:
Others again, out of their fears, objected against it and sought to divert from it; alleging many things, and those neither unreasonable nor improbable; as that it was a great design and subject to many inconceivable perils and dangers; as, besides the casualties of the sea (which none can be freed from), the length of the voyage was such as the weak bodies of women and other persons worn out with age and travail (as many of them were) could never be able to endure. And yet if they should, the miseries of the land which they should be exposed unto, would be too hard to be borne and likely, some or all of them together, to consume and utterly to ruinate them. For there they should be liable to famine and nakedness and the want, in a manner, of all things. The change of air, diet, and drinking of water would infect their bodies with sore sicknesses and grievous diseases. And also those which should escape or overcome these difficulties should yet be in continual danger of the savage people, who are cruel, barbarous and most treacherous, being most furious in their rage and merciless w
here they overcome; not being content only to kill and take away life, but delight to torment men in the most bloody manner that may be.
I could go on quoting Bradford for hours, but this is not the place to do so. What can we learn from him? We learn that the three devils of disunity, shortage of funds, and fear of the unknown are no strangers to humanity. They have always been with us and will always be with us, whenever great adventures are contemplated. From Bradford we learn too how they are to be defeated. The Pilgrims used no technological magic to defeat them. The Pilgrims’ victory demanded the full range of virtues of which human beings under stress are capable; toughness, courage, unselfishness, foresight, common sense, and good humor. Bradford would have set at the head of this list the virtue he considered most important, a faith in Divine Providence.
I end this sermon on a note of disagreement with Bernal. He believed that we shall defeat the Devil by means of a combination of socialist organization and applied psychology. I believe that our best defense will be to rely on the human qualities that have remained unchanged from Bradford’s time to ours. If we are wise, we shall preserve intact these qualities of the human species through the centuries to come, and they will see us safely through the many crises of destiny that surely await us. But I will let Bernal have the last word. Bernal’s last word is a question which Bradford must often have pondered, but would not have known how to answer, as he watched the first generation of native-born New Englanders depart from the ways of their fathers:
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