The Essay by Russell Ciochon on 'The mystery ape of Pleistocene Asia' (Nature 459, 910–911; 2009) and the accompanying News story 'Early man becomes early ape' (Nature 459, 899; 2009) announce that Ciochon has changed his mind about the taxonomic assignment of a 1.9-million-year-old hominoid partial jaw. But on what evidence is this reassignment based?
Whereas Ciochon and his colleagues originally considered the fossil on the Homo line (W. Huang et al. Nature 378, 275–278; 1995), Ciochon now thinks it represents a “mystery ape” and that there is a group of them out there waiting to be discovered.
Although the News story included a photo and illustration of the fossil, I was unable to discern any evidence in either piece for taxonomic justification of the reassignment. I'm not a hominid expert so I'm not qualified to agree or disagree; I would just like to know if there are any anatomical characters — 'synapomorphies', in systematic parlance — that form the basis for this revised judgement, as one would expect for any taxon. If this is merely going with what other people thought, it is unclear why it is considered newsworthy.
Could one not certify what synapomorphies this fossil possesses, and place it at that particular node on the phylogenetic tree? Uncertain characters could then suggest further refinement if more information comes to light. How can one know that there was a “diversity” of Pleistocene mystery apes in southeast Asia without this kind of systematic rigour?