On the Evidences of Inorganic Evolution

ON THE EVIDENCES OF INORGANIC EVOLUTION HARLOW SHAPLEY* To both scholars and laymen the term "evolution" generally elicits only biological pictures—apes that resemble humans, dogs that deviate far from the ancestral wolves, hybrid corn that shames the primitive grain from which it evolved. Evolution and biology are so intimately associated that some may be surprised to find a cold-blooded astronomer in the midst ofdedicated biologists and humanologists. Perhaps I was invited because I sometimes lurk around marine biological stations and at times indulge in observations of the allegedly silly antics ofants and wasps. Now that I am admitted to this company I am inclined, ungraciously, to suggest that terrestrial biological evolution is but a rather small affair, a complicated sideshow in the large evolutionary operation that the astronomer glimpses. This down-grading ofthe human exhibit may not be a popular enterprise , and actually not too justifiable; it may be a bit premature. The cosmogonist, peering under the flap ofthe main tent, has still but a meager prospect of the cosmic circus. However, he can already report loosely onsome ofthebig actsasviewedfromhisawkward positionandequipped, ashe is, with onlyprimitive optics. He maydo much better. The evolution ofhis techniques and his ambitions may eventually justify ranking him considerably above the primal ooze from which his forebears emerged, someten orfifteen galacticrotationsago (two orthree billions ofterrestrial years). The sun shines. The obviousness of that fact is exceeded only by the statement's profundity. For therein lies the answer to those who deny, or at least question, on the grounds of mistaken theological orthodoxy, the occurrence ofany kind ofevolution. * Department of Astronomy, Harvard University. This paper was prepared for the Darwin Centennial Celebration held at the University ofChicago, November 24-28, 1959. 222 Harlow Shapley · On the Evidences ofInorganic Evolution Perspectives in Biology and Medicine · Winter i960 There is nothing miraculous in sunshine. It represents the transfer across space ofenergy that is produced by atomic activities at the surface ofa star. A lighted match is analogous. The match and the sun both send out to surrounding cooler environments their visible and invisible radiations . The energy stored in the molécules ofthe match and in the atoms of the sun flows outward from the hot sources, and by its leaving the masses are reduced. Or, put otherwise, our sun grows less in mass second by second, hour byhour, year by year, simply because it shines. Inevitably and concurrently the volume and density must also change; through radiating the sun evolves, and does so irreversibly. Sunlight requires solar evolution, and the rate ofchange in mass is measured by the basic principle tied up in Einstein's M = E/c2 formula. By extension of the argument, starshine indicates that the billions of radiating stars also evolve. For when a star shines away some ofits storedup energy, E, and therebyloses mass, M, changes in other related properties occur, ofnecessity. Eventually the alterations in mass, temperature, size, and density will be sufficient to affect noticeably the amount ofradiation; and in a long, long time the changes will affect the biological situations on whatever life-bearing planets there may be in the star's family ofdependents . The foregoing preliminary argument aims at two targets: to provide evidence that evolution is a cosmic operation, and to set the stage for inquiries about various facets of inorganic evolution. For example, do nebulae evolve? And star clusters? And even the mighty galaxies? And how about comets? Or, to get more human, how about the evolution ofand on planets; on one in particular? Have the seas and mountains of this planet's crust changed with time? And the chemistry of the oceans and soils? Deepest ofall inquiries for the non-biological evolutionist are questions concerning the mutation of the atoms of which all matter is composed and, at the other extreme of size, the origin, growth, and destiny of the total universe. Many ofthese questions are beyond our present knowing, perhaps beyond the knowable. Before we undertake to present some partialanswers, it might be well to intimate why we cannot hope to present the full and final response. Briefly stated, it is because we are dumb. Congenitally dumb, innately, 223 born in us, and there is...