XIV INTRODUCTION 



"Things living," says Jennings, "behave themselves as if emergent 

 evolution were a true doctrine." 



The acceptance of the doctrine of emergent evolution has greatly 

 relieved the minds of many who were depressed by "mechanical mythol- 

 ogy" as applied to man. According to emergent evolution, man, like 

 all other creatures, is a unique product. Consequently, man's capacities 

 and powers are what we find them to be in experience, and are not to be 

 logically deduced from the properties of lower animals. The doctrine of 

 emergent evolution also relieves the evolution theory of the charge of 

 materialism. If evolution be an emergent process, as it evidently is, we 

 can understand how the "strata" of reality assumed by pluralist philoso- 

 phers have arisen. Out of the lifeless has emerged the living, out of the 

 living the conscious, out of the conscious the ethical. 



This text-book undertakes to answer the questions "Where do we 

 come from?" and "Where are we now?" on the assumption that the 

 human body has evolved. It seems unnecessary and undesirable to 

 present here the mass of evidence gathered by Darwin and his successors 

 in support of this opinion. Most of the facts stated in this book have a 

 bearing, either direct or indirect, upon it. If this book proves anything, 

 it is that the body of man is best understood in the light of its animal 

 origin. 



No attempt is made, however, to convey the impression that evolu- 

 tionary change can be adequately explained at the present time. The 

 hypotheses of Lamarck, Darwin, and De Vries appear today less satis- 

 factory than they did a generation ago, and biologists are still searching 

 for the causes of adaptive evolution. To give students the impression 

 that we know the factors of evolution is to mislead them. A recent text- 

 book states that "it would seem that the immediate cause for the develop- 

 ment of dermal bones from tooth-bases . . . was the early need for teeth 

 and tooth supports in the young carnivorous larvae." Such an assertion 

 evidently raises more problems than it attempts to answer. As a causal 

 factor in morphology, need is probably about as effective as it is in eco- 

 nomic life in raising our balance at the bank. A future advantage or 

 possibility may influence human behavior, but teleology is ruled out of 

 scientific explanations. 



To determine man's ancestry, three kinds of evidence are used — 

 paleontological, anatomical, and embryological. Except for skeletal 

 structures, paleontological evidence is generally incomplete. Con- 

 sequently, for the history of other organs morphologists have to depend 

 upon anatomical and embryological evidence. Unfortunately, evidence 

 from these two sources is sometimes equivocal or conflicting. Ontogenesis 

 does not always repeat the history of the race. There are too many 

 exceptions to the fundamental law of biogenesis. When embryological 



