Franz Weidenreich, in his 1945 article, “The Puzzle of Pithecanthropus”:
It has become almost a rule in paleoanthropology that when a new hominid type is recovered scarcely one is proclaimed as lying in the line which leads to modern man. The type is usually held to be a representative of an extinct side-branch with no bearing on the problem of the ancestry of "Homo sapiens." I do not share this prejudice. As I have repeatedly shown elsewhere there is not the slightest justification for all those claims. They are completely arbitrary and based on purely subjective impressions. We do not know of any morphological criterion which testifies the generic specificity of any hominid form which, so far, has come to light.