The new fossil skull from Dmanisi published this week on Science adds again more questions than answers. The specimens from this site, dated to 1.8 My, display a considerable degree of variation, at the same time showing some resemblance with Homo ergaster, H. erectus, H. habilis, and even with the genus Australopithecus. This last individual has massive facial structures, with a very small cranial capacity which even clashes with the common ranges associated with the human genus. Assuming that all the skulls from Dmanisi are members of the same species, and assuming that morphology is a good indicator for the specie level, the variation at Dmanisi is such that we could lump most of those cited taxa into a single and heterogeneous group. But, of course, there is no reason to think they represent a single species. Most of all, we already know that morphology can be a very bad source of information on species identity. So, why do we paleontologists insist to define species if we know that it is but a meagre speculation? We can put it in nice colours, appealing statistics, and pretty doll-like nicknames. But it is still a personal opinion, not an analytical solution. Of course, we have to call the attention of the media, that’s a good point. But this way paleoanthropology will never be a robust scientific field. If every descriptive study will be associated with firm, striking, and unverifiable statements, we will keep on swinging from one breaking announcement to another, without a solid development of the field. Maybe we have to change a bit the perspective, or even the aims. And maybe we have to focus more on biology and anatomy, their functions, meaning, and evolution, more than keeping on naming rocks.
Posts Tagged 'human genus'
Tags: Dmanisi, human genus, species concept
Tags: frontal bone, human genus, Sheela Athreya
Modern humans are supposed to have a bulging frontal squama, but little quantitative evidence is available on this topic. Most analyses included the browridge, the rest of the vault, or the whole skull, possibly confounding factors associated with the spatial relationships of the frontal bone with the other cranial elements. After the analyses of the frontal width and of the parietal curve in the human genus, here’s a quantitative approach to the curvature of the frontal squama (Am J Phys Anthropol 2013). Modern humans do actually have a more bulging frontal bone, independently upon orientation or position of the squama. Nonetheless, there is some overlapping between modern and extinct variation, suggesting caution when dealing with single specimens. Early modern humans display the same degree of frontal curvature than living modern humans.
See also this recent paper:
Athreya S. 2013. The frontal bone in the genus Homo: a survey of functional and phylogenetic sources of variation. J. Anthropol. Sci. 90:59-80. [pdf]