INTRODUCTION

Major developments have taken place in the field of neuroscience during the last two decades. We have seen an explosion in imaging techniques used in the study of the structure and function of the living human brain, a variety of improved staining and immunohistological techniques used in post-mortem material, different tracing methods, and stereological and quantitative tools among others. Most of these innovative techniques, however, have not yet been incorporated in the comparative study of the primate brain nor in questions concerned with the evolution of the human brain.

There is a large body of knowledge about the brains of several monkey species and in particular about that of the macaque, as well as steadily growing information about the human brain. Nevertheless, very little is known about the brains of the apes and in particular the brains of gorillas and orangutans. The statement made by Tuttle (1986), more than ten years ago is still very much correct: