When new human fossils come to light, it's understandable, and indeed laudible, that scientists can end up disagreeing over what it is that has actually been found. Homo floresiensis is a fascinating recent example, with some scientists claiming that it is a new human species, whereas others claim it is Homo sapiens with a bad case of microcephaly. The jury is still out—although, to this unqualified outsider at least, the argument for its being a new species seems to be winning at the moment.
I was reminded of the Homo floresiensis controversy when I came across the following quote in an 1864 paper by Thomas Henry Huxley entitled Further Remarks upon the Human Remains from the Neanderthal:
M. Pruner-Bey seems to incline to the hypothesis that the Neanderthal man was an idiot: but I confess I find much weight in the pithy reply of M. Broca:-
"Idiocy, competent to produce a cranium of this kind, is necessarily microcephalic; now this skull is not microcephalous, therefore it is not that of an idiot."
Plus ça change. It would appear that microcephaly is not a new explanation for human fossils with small brains.