Volume 1

Evolution after Darwin : the University of Chicago centennial / edited by Sol Tax.

Date:
1960
    not a survival requirement of the Early Pleistocene. Eat, procreate, live it up!—that was the original program for the primates, as it was for our colleagues throughout the animal and vegetable kingdoms. Our human ancestors carried it through, and after many a narrow squeak here we are. After a couple of billion years of competitive terrestrial biology, here we are assembled to assess the foibles and potentials of a few animal species, especially of man. In our anthropocentric eager ness, the cosmos is almost forgotten. As I was saying, the physical orienting of Homo goes on but slowly. That assertion is developed a bit further to show that in power to comprehend we may rightly merit the intimation of inherent incom petence. Does Life Exist Elsewhere? Centuries ago, when the other known planets had been put in their correct places by terrestrial astronomers and recognized as comparable to the earth, speculators began to imagine other planetary biology than our own. The men on Mars, for instance, were exploited. This was all juicy meat for the fiction writers. The non-fictionists, to be sure, granted the possibility of low life on Mars—but life only of a vegetable sort, and not succulent vegetables at that. Martian algae and fungi were admitted as a possibility by those who measure and cal culate about conditions on that cold, dry, thin-aired body. In the past few decades, however, the picture has changed, not relative to the low-life prospects on Mars, but with regard to planets and life elsewhere. Several new scientific developments have joined in this further pin-pointing of the place of man in a universe of space- time and matter-energy. Four of them are (1) the discovery of the center of our galaxy, mentioned above; (2) the new biochemical researches on macromolecules; (3) the measurement of the expand ing universe, and (4) the census of galaxies. All of these can usefully be more fully stated. (1) The globular star clusters first contributed to the locating of the sun and planets on the perimeter of our galaxy, and showed our galaxy to be an immense system of some hundred thousand million stars more or less like the sun. Stellar counts, nebular distributions, stellar dynamics, and more recently radio astronomy have confirmed beyond undoing the peripheral position of the solar family. When spectrum analysis showed that the sun was a typical star, with no outstanding qualities except that it is our parent, our humbling thoughts about the mighty Milky Way increased in depth and coim pass. We began to ask seriously and scientifically if we of the earth
    are the only living things in the universe, or are we merely the local sample of what creation and evolution can do. (2) Other participants in this conference on evolution will fully treat of the great advances recently made in the fields of photosyn thesis, virology, microbiology, and chemical biogenesis. I ask only to insert my conviction that the origin of life is an inevitable step in the gas and liquid evolution on a star-fed planet’s surface when the chem ical, physical, and climatic conditions are right; and the range of right ness can be wide, with much tolerance in the matters of temperature, atmospheric pressure, and the chemical constitution of air and water. (3) That the red-shift of the lines in the spectra of external galaxies must be taken as an indication of the scattering in space of these huge stellar systems is all but universally accepted by the students of the subject. Nearly a thousand of these difficult objects have been meas ured for speed in the line of sight (“radial velocity”). In all directions the same result appears—the more distant the galaxy, the greater its speed of recession from the earthbound observer; and for hypothetical observers in other galaxies the same phenomenon appears. Unques tionably the universe is expanding, the galaxies are scattering. Where are they going? That question is in advance of the times. Where did they come from? To that question we have at least a tentative answer, namely, they came out of some more concentrated state of affairs. For if the galaxies are now scattering, the system of them (which we may call the metagalaxy or the universe) was smaller yesterday—more so last year, and a million years ago. IMPLICATIONS OF THE EXPANDING UNIVERSE We cannot deny, in the light of present knowedge, the evidence that a few thousand million years ago the stars and galaxies were densely crowded together. (We need not go so far as accepting literally Canon Lemaitre’s single Primeval Atom that contained the whole mass of the universe.) In the early crowding, things happened that can not happen now—namely, the frequent colliding and disrupting of stars, whether they were in the same form and size as now or in a protostar state. These collisions were planet-makers and planet dis rupters. Doubtless it was a lively time in the cosmos when our present mul- tillions of stars were a-borning in a medium that was rich in comets, disrupted stars, and planets, in interstellar clouds of gas and dust. Such confusion cannot easily occur now. Our times are relatively quiet; our spatial environment is thinly populated; our sun and its planets move around the galactic center in a calm 200,000,000-year
    cycle. During its past ten or fifteen revolutions our sun has fed with out interruption the plants and animals on its No. 3 planet, quite un disturbed by turbulence such as prevailed in the early days. The point of my excursion into cosmic genealogy is to emphasize the very high probability that millions of planetary births have oc curred in our galaxy and trillions in the other galaxies. If we seek some origin for planetary systems other than the inevitable catas trophes of the crowded early days (for instance, the presently favored neo-Kantian shrinking-nebula hypothesis), the birth of planets is even more common than supposed above. A planetary family would probably be the fate of all stars except those in dense associations, such as double stars and clusters, where perturbations would oust planet making material. (4) The large telescopes have in recent years confirmed the earlier suspicion that the number of stars must be reckoned in what are com monly called “astronomical figures.” From sampling star counts and measures of gravitational attraction throughout our galaxy, we esti mate that the stars in our own system total more than 10 u equivalent suns. (Many of the stars are bigger and brighter than our sun, but a majority are of lesser stature.) IMPLICATIONS OF THE STAR CENSUS Other galaxies are like ours in composition—stars, gas, and dust. With the naked eye we can see three or four. Small telescopes dimly show a thousand; the larger instruments, used photographically, reveal mil lions, and no bottom! About a million are on the Harvard photo graphs; we have measured nearly half for position, brightness, and type. Some of the Californian and South African telescopes go deeper —still no end. Sampling indicates that more than a billion are within our present telescopic reach, which extends out a couple of billion light-years. Why present these dizzy numbers? To emphasize the abundance of stars and its meaning to a conference on evolution. I would place the number as more than 10 20 . These hundred thousand million billion stars are available for the maintenance of life on whatever planets there may be around them. All are radiating the kind of energy needed for photosynthesis and for animal and plant metabolism. Twenty per cent of them are essentially identical to our sun in size, luminosity, and chemistry.
    The Ubiquity of Life The preceding four items have been advanced to support my easy belief that life is a common phenomenon in the universe. As I have put it in earlier discussions of the astronomical and biochemical situa tion, 2 we do not need the supernatural or the miraculous to account for the origin of life on this or other planets, and we have no justifica tion whatever for assuming that long-enduring biological experiments are confined only to the surface of this planet, which circles an ordi nary star out toward the edge of a typical galaxy among the billions. No justification exists for such a retreat toward anthropocentrism, and no reason for not suspecting that the biological heights (complexities) achieved here on Planet No. 3 have been numerously exceeded else where. There may be life (defined as “self-replication of macromolecules”) of a quite different sort from that in which we on earth are evolved; but it seems not to be very likely. Our kind of chemistry is cosmos wide, according to spectroscopic evidence; our major physical laws are not earth-confined. I believe that in view of our experience with a million kinds of organisms on the earth’s surface, we would recog nize livingness on other planets if we could examine and analyze specimens. In this local sample of what creation can do, man has assumed to himself a top position, and with some justification. To be sure, in his information-receivers—the sense organs—he is by other animals fre quently outdone in sensitivity or range or both; better vision is found elsewhere, keener hearing, richer smell and taste, more sensitive touch. If he had always excelled every species in all these paths to reality, he might long ago have acquired a better mind for intellectual problems. Other sense organs are conceivable. Man is wholly without effec tive organs for the recording of some physical phenomena, knowledge of which might open the door to better perception and fuller under standing. Magnetic phenomena, radio waves, even infrared and ultra violet radiation, are not naturally available to him through sense or gans. His brain apparently has not developed, with respect to excita tion from such sources, as it has developed with respect to light, sound, touch, and smell. Among the billions of life-operating planets that probably exist in the universe there must be many where the highly sentient organisms are more fully and more effectively equipped than 2 Shapley, Of Stars and Men (Beacon Press, 1958).
    are the Terrestrials for informative reactions to external and internal environments. It is for this reason that I point out our deficiencies and our probably inborn incompetence. Inorganic Evolution: The Evidence To carry out the undertaking assumed in the title of my contribution, which has been only indirectly faced up to so far—that is, to present the case for inorganic evolution in the light of current thought—I plead inability to give a durable account because of today’s rapid de velopments in observation and interpretation and because of the fra gility of a number of the prevailing hypotheses. A few pages will suffice to show the trends of speculation on evolution for each of the most important areas: the material universe, the chemical elements, the galaxies, and the stars and planets. Those who report to this con ference on paleontology and related subjects will presumably have concerned themselves to some extent with the evolution of the earth’s crust, its oceans, and atmosphere. ORIGIN OF THE UNIVERSE Currently two incomplete and not very satisfactory hypotheses on the origin of the material universe have been seriously proposed and ex plored. In their present development one theory can be identified through associating it with the names of Lemaitre and Gamow, and the other, with Bondi and Gold, and Hoyle. In dealing with such ancient, complicated, and mysterious matters as the origin of the universe, we are hardly concerning ourselves with science in sensu strictu. The subject is stained with metaphysics, reli gion, and mental aberrations. The primeval-atom theory. —To put it briefly, Canon Lemaitre and his followers (there are not many of them) postulate an all- inclusive Primeval Atom, the radioactive bursting of which, some 10 10 years ago, was The Creation. It is suggested that time and space also first appeared when the burst of the Primeval Atom inaugurated the expanding material universe. Immediately after the burst (an odd way to put it!) the well-known natural laws took complete charge, and what is now observed in the macrocosmos and the microcosmos has been the “natural” development of the universe. The natural opera tions include the scattering of the galaxies as a consequence of cosmic repulsion over-riding gravitation, and include the creation of the heavy chemical atoms out of quanta of energy and the proton-electron- neutron-positron-meson basic corpuscles. But this hypothesis, without considerable refinement and protection by sub-hypotheses, gets into