Human Evolution and Morphometry

[Frans_Jozef]

http://www.anthropology.at/basis.htm...th/morpho.html

Human Evolution and Morphometry


Horst SEIDLER
Katrin SCHÄFER
Hermann PROSSINGER
Philipp GUNZ
Philipp MITTERÖCKER
Bence VIOLA
Markus BERNHARD
Simon NEUBAUER



The work of this group is in close co-operation with the Virtual Anthropology- and the Stereolithograpy group but focuses mainly on the analysis of brain development during human evolution and the application of geometric morphometrics

The combination of CT-data and the use of geometric morphometrics to investigate aspects of fossil hominid morphology is of relatively recent origin but has the potential to contribute significantly to our understanding of internal morphology as well as the overall dimensions of incomplete or fossil skulls.

Median-sagittal sections of various homoinid crania
left: Pan, Bodo, Petralona, Guattari
right: Sts 5, Kabwe,
Atapuerca, H. sapiens

[Frans_Jozef]

Geometric Morphometrics

The advantage of applying morphometric analyses to the regions of interest is that they permit additional statistical quantification of morphological observations, only some of which are possible using traditional techniques (such as distance and angle statistics).
Observations of shape made by traditional morphologists may be confirmed and therefore expressed with greater confidence, and the relative size changes that occurred during hominid evolution can be detailed further and better quantified with these geometric morphometric methods.
Although traditional metric techniques might occasionally be able to determine the combination of change in size and shape as something like a change in form, they certainly cannot distinguish variation in size from variation in shape. Because modern geometric morphometrics is able to statistically quantify size and shape changes independently, variation (and lack thereof) in important morphological features could be discovered.

[Frans_Jozef]

Comparing Frontal Cranial Profiles in Archaic and Modern Homo by Morphometric Analysis
The Anatomical Record (New Anatomist) 257, 217-224 (1999)

FRED BOOKSTEIN,
KATRIN SCHÄFER,
HERMANN PROSSINGER,
HORST SEIDLER,
MARTIN FIEDER,
CHRIS STRINGER,
GERHARD W. WEBER,
JUAN-LUIS ARSUAGA,
DENNIS E. SLICE,
F. JAMES ROHLF,
WOLFGANG RECHEIS,
ATO J. MARIAM AND
LESLIE F. MARCUS

Archaic and modern human frontal bones are well known to be quite distinct externally, by both conventional visual and metric evaluation. Internally this area of the skull has been considerably less well-studied. Here we present results from a comparison of interior, as well as exterior, frontal bone profiles from CT scans of five mid-Pleistocene and Neanderthal crania and 16 modern humans. Analysis was by a new morphometric method, Procrustes analysis of semilandmarks, that permits the statistical comparison of curves between landmarks. As expected, we found substantial external differences between archaic and modern samples, differences that are mainly confined to the region around the brow ridge. However, in the inner median-sagittal profile, the shape remained remarkably stable over all 21 specimens. This implies that no significant alteration in this region has taken place over a period of a half-million years or more of evolution, even as considerable external change occurred within the hominid clade spanning several species. This confirms that the forms of the inner and outer aspects of the human frontal bone are determined by entirely independent factors, and further indicates unexpected stability in anterior brain morphology over the period during which modern human cognitive capacities emerged.

Five archaic crania superimposed on the consensus profiles (inner and outer) of theHomo sapiens profiles obtained by full Procrustes fit to the inner ones. The speckled (narrow) band is the consensus bone cross section between inner and outer profile in the mid-sagittal plane, while the grey band approximates the individual cross section for each archaic cranium.

[Frans_Jozef]

Relative warp scores (principal component scores for Procrustes-registered shape co-ordinates) of the mid-sagittal frontal profiles. Solid symbols: Homo sapiens; open symbols: fossil Homo (Bodo, Kabwe, Atapuerca, Petralona, Guattari), * Mrs. Ples, + Pan troglodytes ). Axes are in units of Procrustes length throughout.

right: The samples are widely separated on the first relative warp of outer profile shape.

left: The relative warp scores for inner profile shape show overlap between the samples.

[Frans_Jozef]

Consequently, many fascinating questions suggest themself: at which other positions of the skull have major shape and size changes taken place? and Could it be that the exocranium is involved in shape changes while the endocranium in size changes?
We approach these questions by analyzing the general shape and size of both the exo- and endocranium. Importantly, because the inner surface at the braincase provides cranial information concerning brain evolution and because of the syn-evolution of cerebellar and frontal lobes (Seidler et al., 1997), our investigations also include the occipital bone.

Another complex of questions is the following: how do these results relate to the shape of the frontal cranial profile of subadult Homo? Or, more precisely, do modern as well as archaic infants, children and juveniles exhibit the same shape, or if not, in what way do they compare with results found for the adults? Does the inner table curvature stay invariant during the ontogeny of Neanderthal and modern individuals? What happens to the outer table during this time? Is there a dislocation between inner and outer table relating to the growth of the paranasal sinuses? At what stage of ontogeny does the Neanderthal outer table acquire a specific Neanderthal morphology? To what extent does the ontogeny of H. sapiens children resemble that of Neanderthal ones?

[Agrippa]

Very interesting post and a good study for a better understanding of human evolution.