This book discusses how and why animals evolved into particular shapes. The book identifies the physical laws which decide over the evolutionary (selective) value of body shape and morphological characters. Comparing the mechanical necessities with morphological details, the author attempts to understand how evolution works, and which sorts of limitations are set by selection. The book explains morphological traits in more biomechanical detail without getting lost in physics, or in methods. Most emphasis is placed on the proximate question, namely the identification of the mechanical stresses which must be sustained by the respective body parts, when they move the body or its parts against resistance. In the first part of the book the focus is on 'primitive' animals and later on the emphasis shifts to highly specialized mammals. Readers will learn more about living and fossil animals. A section of the book is dedicated to human evolution but not to produce another evolutionary tree, nor to refine a former one, but to contribute to answering the question: "WHY early humans have developed their particular body shape".

The hand commonly is considered to have exerted great influence on the evolution of typically human characteristics, like upright posture, stereoscopic vision, "manipulative" handling of parts of the environment. The German term "Begreifen", which is commonly used for the understanding of complex relationships in a generalised, abstract sense, always implies the original meaning of seizing objects with the aid of the hands. The hands are also of greatest importance for the survival of the other, non-human primates. Hands are absolutely essential for locomotion in an arboreal habitat, and the intake of food is dependant on the use of the hands as well: primates very rarely take in food directly with their mouths, in the wast majority of cases they seize food items with their hands. Even drinking is often performed by dipping the hand into the water and licking the drops from hand and forearm. An organ of such importance will very probably be "adapted" to its "function". This statement is made so often, that any further considerations seem superfluous. Nobody doubts, that the hands of primates are highly adaptive organs, the general form and internal structure of which are closely related to the necessities of life. However, if one tries to go beyond this general statement, he finds himself confront ed with several problems: First of all, a point which W. GUTMANN has emphasized repeatedly: according to the results obtained by genetics, the first thing to appear is the mutated character.