Fossil hands

[Mikey Brass]

Functional capabilities of modern and fossil hominid hands: Three-dimensional analysis of trapezia (p 101-112) , M.W. Tocheri, M.W. Marzke, D. Liu, M. Bae, G.P. Jones, R.C. Williams, A. Razdan , American Journal of Physical Anthropology, Volume 122, Issue 2 (October 2003)  


ABSTRACT Three-dimensional (3D) trapezium models
from Homo sapiens, Gorilla gorilla, Pan troglodytes,
Australopithecus afarensis (A.L.333-80), and Homo habilis
(O.H.7-NNQ) were acquired through laser digitizing.
Least-square planes were generated for each articular
surface, and the angles between the planes were compared.
Each extant species displays an overall pattern
that distinguishes it from the others. The observed angles
in G. gorilla and P. troglodytes are more similar to one
other than either is to H. sapiens. Our results, obtained
from using new 3D modeling and analytical tools, raise
interesting questions about the functional capabilities of
the fossil trapezia. Multivariate statistical analyses indicate
that A.L.333-80 is morphologically more similar to
that of modern humans, whereas the O.H.7 trapezium is
more similar to that of the gorilla. Significant differences
between A.L.333-80 and the extant species occur, but
some similarities to humans suggest the ability to form
the distinctively human forceful pad-to-side and three-jaw
chuck grips. Some key morphological differences from humans
highlighted and quantified by our research suggest
limitations in the functional capabilities of the O.H.7 trapezium,
particularly in those that facilitate pronation at
the base of the second metacarpal. If the O.H.7 trapezium
represents part of the hand responsible for manufacturing
and using the stone tools found at Olduvai, our results
suggest that the hand manipulated the stones in a way for
which we have no modern analog. Alternative considerations
are that the O.H.7 trapezium is not representative
of other trapezia from its species (i.e., N = 1), or that it
represents another primate or hominid species.

[dholeman]

This abstract reminded me of recent work in 3d shape classification and pattern recognition:

http://www.cs.princeton.edu/~chazelle/pubs/smi01.pdf , a paper titled "Matching 3D Models with Shape Distributions, R. Osada, T. Funkhouser, B. Chazelle, D.P. Dobkin, Shape Modeling International (2002), 154-166. Also in ACM Transactions on Graphics, to appear. ".

The idea is that digital renderings such as these (pun intended) can be analyzed using bayesian statistical techniques to identify and categorize the component shapes.  From a corpus of such renderings it would be possible to classify the rendered objects in an entirely objective manner.

For instance, a collection of hundreds (say) of phallanges could be classified statistically and the resultant metrics could then be combined with other data to label the classifications anthropologically.

Nor is there any reason that the technique should be limited to bones. A rigorous test of lithic toolkit classifications would be to subject them to a similar automated discriminant analysis. Ornaments, pottery and weapons come to mind as well.

[alantranscraft@sof]

I liked the mention of throwing! The topis is now almost mainstream.

Has anyone mentioned that the same gene that governs bigtoe size alos governs thumb size? There is a rare affliction that can cause both to be "runt sized" (there is a well-known case in Brazil). If bi-pedalism was the driving force of hominid evolution, the thumb was something of a spi-off benefit...

Alan