JuxE, 1930 



EVOLUTION 



Page three 



How Evolution Works 



By H. J. MULLER 



/. IS EVOLUTION A ''FACT?" 



IS evolution "a fact?" Am I a fact? AVhat is a 

 fact? The philosopher says that he can not 

 say I am a fact, but that he knows he is a fact, 

 and that that is all he Jcnows for sure, but I am 

 not sure he knows that much. However. I will not 

 dispute it with him. He and I and evolution may 

 all be a hoax, but I think we have enough evidence 

 to convince us that we will all have to stand or fall 

 as hoaxes together. And that is enough to satisfy 

 me, at the present stage of the game. If I am a 

 hoax, you may be sure then there is no evolution, 

 and if evolution is a hoax you may be sure there 

 is no me, but if either 

 evolution or I exist, then 

 you need not doubt that 

 the other exists too, and 

 by the same token: for 

 it is by the same process 

 of piecing together, in- 

 terpolating, a kind of con- 

 tinuity in the intervals be- 

 tween the separated but 

 ► consistent mo m e n ta r y 

 glimpses of us which you 

 get sense evidence of from 

 time to time, that you can 

 reconstruct a convincing 

 concept of each of us, H. J. MULLER 



evolution and me. Certainly, if any one could prove 

 that evolution had not occurred, in spite of the over- 

 wlielming evidence we have of it, I should have my 

 conception of the consistency of the universe so 

 destroyed that I should see little reason left to 

 credit the truth of my own existence. So remember, 

 if you will, evolution is not a fact — no, not at all — 

 no more a fact than that I exist or that you are 

 reading the words on this page. 



It ill befits us, however, to remain wrangling over 

 such abstractions when we stand confronted with 

 the view of a great hitherto unknown world of which 

 we form a part. Admitting, for purposes of living, 

 the reality of this world of ours, we must forthwith 

 bestir ourselves to find out its possibilities and the 

 rules which govern its activities. Even though we 

 may be but as little motes drifting helplessly in its 

 great currents, still we can not keep our self-respect 

 as men without striving to understand its oper- 

 ations, and, if possible, to make at least some little 

 •impression upon them. What, then, are the methods 

 of operation of these great evolutionary processes 

 in which all life has been caught? 



This article, given originally as a public lecture on 

 "the Method of Evolution" at the University of Texas 

 May 6, 1929, has been brought up to date by the author. 



//. THE QUARREL OVER THE CAUSATIVE 

 AGENT 



It is here that the real doubt and divergence of 

 opinion among the so-called "experts" has been sup- 

 posed to exist. "Darwinism is dead," it is ,some- 

 times parroted, and tiiough Kammerer died trag- 

 ically by his own hand, the hypothesis of the inheri- 

 tance of acquired characters which he among others 

 advocated is claimed to have plausibility. Many, 

 if not most, medical men still believe in it, but some 

 philosophers prefer evolution through a kind of 

 inner drive — "orthogenesis ;" still others who make 

 themselves heard believe that instead, or in addition, 

 there is a direct influence of the kind of environment 

 upon the kind of variations that occur, with the 

 result that fitter and fitter, or occasionally, less 

 and less fit, organisms are brought into being. To 

 "explain" the fortunate adaptive responsiveness on 

 the part of the organism, the guesses range from an 

 internal, rather short-sighted, cell-intelligence, the 

 "enteleche," to an external, far-visioned perfect- 

 ing principle. 



Amongst the various voices — so our students 

 have to learn from some contemporary texts — there 

 are also to be heard the voices of "neo-Darwinians," 

 who arrive at a finite end by an almost infinite num- 

 Ijer of steps, or slides, back and forth, of almost 

 zero individual magnitude, the backslides, however, 

 being each time discontinued. And opposed to these, 

 it is often stated, are the voices of different kinds 

 of "mutationists." Some of the latter would have 

 one adapted species change directly into a differ- 

 ently adapted species by just doing so; others 

 would have each more advanced type emerge out of 

 the more primitive type by losing an inhibition. 

 Then, too, there are the voices of those claimants 

 who say that new products arise only by the cross- 

 ing of preexisting types, followed by the formation 

 of a combination type representing certain elements 

 from each of the old. It is not explained here 

 whether the second species arose by crossing between 

 the first and third or whether the third species arose 

 by crossing between the first and second, or both. 

 Altogether, you see, this is not a process of a species 

 raising itself by its bootstraps — not so crude. Here 

 A lifts B's bootstraps, and B lifts A's, onward and 

 upward forever! 



After such a maze of opinions, of which these 

 form only a part, the slate is left pretty blank (or 

 rather, evenly scrawled over) for the teacher, the 

 student or the outsider to write in, large, his own 

 personal beliefs. Among these, there is one com- 

 mon. It starts out by stating that every effect 

 has its cause, and a definite effect has a definite 

 cause, and goes on to say that therefore it is only 

 reasonable to suppose that a definite kind of varia- 



