Originally published in 1972, Homo Sapiens examines how humans emerged from among the millions of other species and achieved our unique position within the animal kingdom. The book examines what direction future evolution will take and what may be regarded as the 'meaning' of human existence. It stipulates that these are the questions for which no real basis of discussion existed before the 20th century, and at the time of publication, some were still without a definite answer. The book sets out analyse these questions and the continuing debate that has arisen from their study. This is an account of the uniqueness of man in the animal kingdom, how this uniqueness arose during evolution, and what traces of it can be detected in animals other than man. The book describes the mental and physical evolution of man, from his earliest ancestors to the present day. He also gives an account of man's cultural development seeking to establish that there is an underlying principal of cultural evolution, a principle that has been denied by many historians. Later chapters deal with the future and with possible forecasts of mankind's further physical, intellectual and cultural evolution.

Originally published in 1972, Homo Sapiens examines how humans emerged from among the millions of other species and achieved our unique position within the animal kingdom. The book examines what direction future evolution will take and what may be regarded as the 'meaning' of human existence. It stipulates that these are the questions for which no real basis of discussion existed before the 20th century, and at the time of publication, some were still without a definite answer. The book sets out analyse these questions and the continuing debate that has arisen from their study. This is an account of the uniqueness of man in the animal kingdom, how this uniqueness arose during evolution, and what traces of it can be detected in animals other than man. The book describes the mental and physical evolution of man, from his earliest ancestors to the present day. He also gives an account of man's cultural development seeking to establish that there is an underlying principal of cultural evolution, a principle that has been denied by many historians. Later chapters deal with the future and with possible forecasts of mankind's further physical, intellectual and cultural evolution.

Evolution of Castes in Insects l BERNHARD RENSCH The evolution of organisms in the succession of generations has been primarilly achieved through the appearance of new hereditary variants with minor deviations along with the development of stable structures and functions. Harmful mutants were eradicated either immediately or in the subsequent generations through the process of natural selection while unharmful or advantageous ones usually survived. As this process continued, many new races and species developed which possessed structures and functions of a rational nature and which became increasingly independent from their environment. These evolutionary tendencies were also promoted through either geographical, ecological, physiological or genetical isolation of populations. In some phylogenetic lines, there occurred an increase in the number of cells due to additional cellular divisions in the morphogenesis of structures. This opened up the possibility for the development of the division of labour within cellular groups leading to more complicated and consequently more successful functions of tissues and organs. A further advancement in the adaptation of a species to its environment was made possible through specialization for certain functions of whole individuals or groups of individuals.

1. Our understanding of the localization, formation, and arousal of memory traces, of the process of abstraction and generalization and of the psychophysical relations of all these processes is still very unsatisfactory in spite of thousands of relevant investigations. The author comments several findings of different researchers, gives a summary of his and his coworkers' relevant investigations and discusses briefly some possible hypothetical conceptions. 2. Up to now the extension of nervous structures which are involved in the formation of engrams is not sufficiently known. It is also not clear whether or not brain regions of sensations and regions of corresponding mental images are identical (Fig. 1). During learning processes excitations in relatively extensive brain regions occur (Fig. 2). In mammals the brainstem and the midbrain and especially the hippocampus formation can be involved. These statements strengthen the opinion that the formation of a simple memory trace takes place in a network which comprises very many neurones.

The problem of memory and capability of abstraction and generalisation is discussed with special reference to investigations performed in the Zoologi- cal Institute of Munster during the last 15 years. The main statements are the following ones. When related species or races of the same species of different body size are compared the capacity 0/ learning and duration 0/ memory is positively correlated with absolute brain size. In some cases the absolute size of the brain seems to be more important than its special structure and the phylo- geneticallevel of the animals. The maximum of similar optical tasks mastered at the same time was: Octopus 3, trouts 6, Iguana 5, a giant race of domestic fowl 7, Indian elephant and horse 20. Normally, memory lasts a very long 1 time. A horse retained 19 of 20 optical tasks 1 /2 year, a carp one task more 1 than 20 /2 months. The capability of abstracting also depends upon the absolute brain size. Examples are given for the capability of abstracting with regard to sensa- tions of touch (experiments with a racoon) and to hearing (experiments with jackdaws and parakeets).