240 J. C. MERRIAM EARTH SCIENCES, BACKGROUND OF HISTORY 



The fluctuations in physical conditions on the earth in geologic time have, 

 therefore, great significance in consideration of the larger problems of 

 earth history. 



It is not my purpose to bring into review, or to discuss, the tremendous 

 field for evolutionary studies in the groups of animals and plants whoso 

 history we find represented in the rocks. One after another these have 

 been considered by specialists in various fields. In all cases, the laws of 

 which I have just spoken find expression, whether this be in the evolution 

 of the nautilus, dinosaur, or elephant. Given lapse of time and change of 

 environment, and the old goes out the new comes in, the unspecialized 

 gives way to the specialized. As the ages go by, in each successive step, 

 almost without exception, we find a higher level of life, representing 

 greater intelligence, greater efficiency, and greater progress. 



The most interesting of all the series of fossil forms represented in the 

 geological record, and the most interesting in the first instance because 

 the series begins well back in the geological record, is that succession 

 giving us the beginnings of the race of man. The earliest known traces 

 of human beings represent a normal part of the life of the earth in a 

 period so remote from the present that our calculations must be in terms 

 of eons rather than of millenniums. We find that since these first man- 

 like forms appeared great crustal movements have changed the face of 

 the earth, and that the climate has shifted back and forth many times 

 through relatively wide ranges of temperature. We know also in this 

 period a long procession of living generations of animals other than man 

 passing through the ages and disappearing. 



We find the first remains of humans more beast-like than any living- 

 race, approaching ape-like forms both in skeleton and skull, and meeting 

 the requirements of the missing link. We find this first stage followed 

 by others still different from man of the present day, but approaching, 

 more nearly to the modern type. The laws applicable to the evolution of 

 other groups apply to man. We note the same relation of physical change 

 in man to lapse of geologic time, to climatic and crustal change, and to 

 other factors in the physical history of the earth. So far as the evidence 

 goes, it meets the requirements of those who assume the emergence of 

 man from the animal in the manner in which innumerable other organic 

 types have arisen in the long life record as we know it. 



Through still later stages of the geological and paleontological record 

 man advanced in intelligence and culture, his environment gradually 

 approximated present conditions in both physical and biological factors^ 

 and we record the history of these stages partly in terms of archeology, 

 whicli in turn merges into history based on written records. 



