March, lt'29 



E \' O L U T I O N 



Page Three 



A'ikI present-day astronomers find two big dif- 

 ficulties. First "it can be proved that an extended 

 tenuous ring would not condense into a single body, 

 but into many bodies, like the asteroids or the rings 

 of Saturn. Second, 98 per cent of the angular mo- 

 mentum of the solar system is at present associated 

 with the orbital motions of the planets, comprising 

 only l/700th of its mass. The total angular nioment- 

 inn cannot be altered by any internal changes within 

 the system, and no process has ever been imagined by 

 which 98 per cent of it could have been segregated in 

 less than l/700th of its mass." 



The nebular theory attempted to explain the origin 

 of the solar system under the action of forces entirely 

 within the system, but this is now believed by many 

 astronomers to be impossible. The present distribution 

 of angular momentum is believed to be due to forces 

 from the outside of the system. 



About twenty years ago Chamberlain and Moulton 

 of the University of Chicago proposed an alternative 

 theory which overcomes the difficulties. According 

 to this theory, our sun in the remote past was a star 

 without planets. Another such sun in journeying 

 through space came so close to our sun as to cause a 

 tremendous disturbance, pulling out great masses of 



the sun and starting them on their revolutions. By a 

 kind of explosion, due to the disturbance of gravity, 

 myriads of these masses were projected into space, 

 the so-called planetesimals. Not only was this new 

 theory free from the fatal difficulties of the nebular 

 theory, Init it explained many features of the solar 

 system and pointed to a common origin by an orderly 

 process. 



The myriads of planetesimals left revolving around 

 the sun were slowly gathered together by the action 

 of gravity into planets, satellites and asteroids. Per- 

 haps meteors and comets are stray planetesimals. 



The craters on the moon, some believe, were of 

 volcanic origin, but there is much to favor the theory 

 that they were caused by the impact of planetesimals 

 or meteorites. 



Among recent modifications of the planetesimal 

 theory should be mentioned the tidal theory of Jeans 

 and Jeffreys who agree in the encounter between our 

 sun and some other star, but differ as to the dynamic 

 details. 



The age of our solar system, since the great cata- 

 strophe which started its development, is estimated 

 with great probability to be from five to ten billions 

 of years. 



The Origin of Man from the Anthropoid Stem 



When and Where? 



(From Bicentenary Number of American Philosophical Society's Proceedings, Vol. LXVI, I9Z7) 



By WILLIAM K. GREGORY 



IN his recent articles on the origin of man Professoi 

 Osborn rules the apes out of the line of ascent to 

 man on the ground that they have ape brains and ape 

 minds, that they have degenerate thumbs and limbs 

 adapted for acrobatic life in the trees, that they walk 

 on all fours and have grasping hind feet. 



Anti-evolutionists of all schools are doubtless re- 

 joicing in the fact that Professor Osborn has re- 

 pudiated man's descent from apes and has brought 

 forward with all the authority of his name some of 

 the very points which they have long been stressing. 

 But their exuberance will be dampened somewhat when 

 they realize that Professor Osborn, like Professor 

 Wood Jones, separates man from the apes only in 

 order to derive him eventually from a far lotver branch 

 of the primate stock. 



Out of all the confusing tangle of resemblances and 

 differences between men and apes, opponents of Dar- 

 win's solution of the problem have regularly seized 

 upon a few of the more evident differences, to which 

 they have given wide publicity. But they have con- 

 sistently ignored or depreciated the mass of positive 

 marks of kinship visible in the very early embryonic 

 . stages of apes and men, as well as in adult anatomy 

 and in profound physiological reactions. 



This evidence as to man's kinship with the apes is 

 always weakened by being cited in small quantities, 

 since its logical value lies in its cumulative weight. 

 The defender of the Darwinian view is trulv at a 



disadvantage precisely because his evidence is too 

 extensive to be fully exhibited to his opponents. On 

 the other hand, some who oppose Darwin's derivation 

 of man from the apes imagine that they have raised 

 serious objections to it, if they can cite even a few 

 characters wherein modern man and ape dift'er. 



Obviously there are many differences between man 

 and the modern apes. If it were not so, there would 

 either be no apes or no men and the problem would 

 not now be under discussion. The first vital question 

 is, are the characters, many or few, that are common 

 to men and apes, due to inheritance from a more 

 remote common stock, or are they due to parallelism? 

 If the latter, if it still be admitted that man belongs 

 in the order Primates, to what group other than the 

 great apes is he most nearly related, by what steps 

 has he diverged from that group, in what part of 

 the world may we search for his ancestors and how 

 shall we recognize such ancestors when we find them? 



These questions in turn are quite obviously tied up 

 with the general problem of the classification and 

 geographic distribution of the families and subfamilies 

 of the tree-shrews, lemurs. South American monkeys. 

 Old World monkeys, apes and mnn, both recent and 

 fossil. Since 1910 I have published a series of care- 

 fully worked oitt analyses of these problems, in which 

 the Darwinian view of man's origin has been steadily 

 tipheld. The opponents of this view have not met 

 the issues discussed in these papers. They have not 



