Ever since their description by Dubois (1920, 1922) the Wajak skulls Java) have played an important role in the discussions on the evolution of modern humans in Australasia. Because of the robust morphology of the skull, Wajak Man was seen as a link between Pleistocene hominids from Java (Solo) and Recent Australian Aborigines. However, for a long time hardly any attention has been paid to the contents of the other boxes with human, faunal and cultural remains, as collected by Dubois around 1890. Because a satisfactory description of the Wajak fossils has so far been lacking and the archaeological context of the Wajak site has so far been ignored, the evolutionary position of Wajak Man necessarily remained unclear. The present study suggests that the evolutionary significance of the Wajak skulls can no longer be seen in terms of a Late Pleistocene transitional form between the Middle Pleistocene Solo skulls and Recent Australian Aborigines, nor can they be seen as proof of a gracile link between Chinese and Australian populations. Rather, the significance of these skulls is that they give some insight into microevolutionary processes that have taken place on Java itself. The most likely interpretation is to consider the Wajak skulls as Mesolithic robust representatives of the present inhabitants of Java. According to the hypothesis presented at the end of this thesis there are two species within the genus Homo in Australasia: Homo erectus and Homo sapiens. Within Homo sapiens one can recognise in Australasia two main types: a Sunda type (Chinese and Javanese) with strong neotenic trends, and a Sahul type (Papuans and Australians) which is closer to a generalised Homo sapiens morphology. Wajak-1 (Java) and Liujiang (China) possibly represent the earliest clear examples of the Proto-Sunda type (proto meaning more robust). Hence, they are from this point of view, very important skulls when trying to understand the origin of the Sunda people. Gracilisation of the human skull, as has occurred since the Late Pleistocene, has been reported from different parts of the world. Various explanations have been proposed for their occurrence, like the development of agriculture and climatic changes. To explain the worldwide decrease in size of the human body one could seek for a phenomenon that also has a global character. I propose the idea that because of population increase, technological innovations and rising temperatures, since the Late Pleistocene, various aspects of human life changed (like relaxation of predation, decrease of home range and mobility and increasing symbiosis with other organisms), which enabled an overall decrease in body size.