Science: Evolution Before Life

Some time, some place in the dark backward and abysm of time, the first “living” thing was created, and evolution began. But even the simplest organism is made up of enormously complicated chemical compounds. How were these compounds produced in the slow aeons of the world’s beginnings? Last week Dr. Melvin Calvin, professor of chemistry at the University of California, described some probable steps in the strange, speculative science of chemical evolution that led to the first glimmer of life.

Most pre-evolutionists agree, said Dr. Calvin, that life first appeared something like 2 billion years ago when the earth’s atmosphere was dominated by hydrogen compounds such as methane, ammonia and water vapor. Such simple organic compounds as acetic acid and glycine (an amino acid) are formed in the laboratory when ultraviolet light or electric sparks pass through such mixtures. Presumably, solar ultraviolet and natural lightning would do the same in nature.

Young Earth. While the young earth was still raw some 5 billion years ago, Dr. Calvin believes, great quantities of these relatively simple organic compounds were formed out of the nutritious atmosphere. But, he points out, the very agents (light, radiation) that form these compounds tend to break them down, and thus produce equilibrium far below the living level. Obviously, some other processes were at work.

One of them was probably autocatalysis—the process by which a substance, as soon as a little of it is formed, speeds the formation of more of itself. This process is common in organic chemistry. Many molecules important to life are autocatalytic, and in the soupy ocean and suffocating atmosphere of the young earth their concentration would tend to increase. The porphyrins, for example, which are related to the hemoglobin of animal blood and the chlorophyll of green plants, are autocatalysts.

Many of these simple organic compounds have large, flat molecules that tend to drop out of even a very dilute solution. When they precipitate, these flat molecules produce layered structures, like playing cards scattered thickly on the floor. But they arrange themselves more neatly than cards do. Their edges tend to stick together, and thus the molecules build up into orderly stacks. The porphyrins do this, and so do the components of DNA (deoxyriboenucleic acid), the heredity-carrying substance that dominates life on earth.

Nameless Progenitor. Dr. Calvin sees chemical evolution fairly clearly up to DNA, but he cannot say just when the spark of life appeared. The best test of life is that the organism can make replicas of itself, taking as building materials the simpler molecules in the medium around it. The first organism to pass this divide between the living and the inert may have been a single complex molecule or a large cluster of them. This tiny, nameless primogenitor of all living matter may have used some primitive kind of photosynthesis to reproduce itself. Or perhaps it merely picked up smaller molecules in a series of random accidents. Dr. Calvin does not know.

If such processes produced life on earth, then in all likelihood they produced life on other planets. Dr. Calvin accepts the reasoning of modern astronomers that in the visible universe there are probably 100 million other planets with well-organized life on them. Such life may range all the way from “precellular” micro-organisms to sentient beings who speak a language. Since the life of man on earth occupies only the small span of 1,000,000 years out of the accepted time span of 5 billion years for the universe as a whole, it seems obvious to Dr. Calvin that on other planets life may have developed to a “posthuman” state, in which creatures on man’s level have been succeeded by some higher organism. Dr. Calvin’s conclusion: “Life is not a rather special and unique event on one of the minor planets around an ordinary sun at the edge of one of the minor galaxies in the universe,” but “a state of matter widely distributed throughout the universe.”

Cosmic Influence. The kind of life that exists on earth, Dr. Calvin points out, has reached a critical stage. The highest product of its evolutionary chain—man—is on the point of learning how to navigate space and spread beyond the earth. “There is no reason to suppose that life, and man as its representative, will not transform any planet on which he lands, in the same way, or even in a more profound way than he has transformed the surface of the earth. It might suit him to change the orbit of the moon, and it seems within the realm of possibility that he should be able to do so. When we realize that other organisms may be doing similar things at some millions of regions in the universe, we see that life itself and man, as one representative of that state of organization of matter, becomes a cosmic influence himself.”