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Euclides
Monday, July 12th, 2004, 08:30 PM
Proc Natl Acad Sci U S A. 2002 Feb 5;99(3):1134-9. Epub 2002 Jan 22.


The evolution and development of cranial form in Homosapiens.

Lieberman DE, McBratney BM, Krovitz G.

Department of Anthropology, Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA. danlieb@fas.harvard.edu

Despite much data, there is no unanimity over how to define Homo sapiens in the fossil record. Here, we examine cranial variation among Pleistocene and recent human fossils by using a model of cranial growth to identify unique derived features (autapomorphies) that reliably distinguish fossils attributed to "anatomically modern" H. sapiens (AMHS) from those attributed to various taxa of "archaic" Homo spp. (AH) and to test hypotheses about the changes in cranial development that underlie the origin of modern human cranial form. In terms of pattern, AMHS crania are uniquely characterized by two general structural autapomorphies: facial retraction and neurocranial globularity. Morphometric analysis of the ontogeny of these autapomorphies indicates that the developmental changes that led to modern human cranial form derive from a combination of shifts in cranial base angle, cranial fossae length and width, and facial length. These morphological changes, some of which may have occurred because of relative size increases in the temporal and possibly the frontal lobes, occur early in ontogeny, and their effects on facial retraction and neurocranial globularity discriminate AMHS from AH crania. The existence of these autapomorphies supports the hypothesis that AMHS is a distinct species from taxa of "archaic" Homo (e.g., Homo neanderthalensis).

Skando-naivian-Girl
Tuesday, July 13th, 2004, 07:09 AM
Is human brain size still increasing or is it that this has stopped and a from inside(structure wise/wiring) is taking place?

You seem like an expert:)

Agrippa
Tuesday, July 13th, 2004, 12:58 PM
I think neither, cause there is no effective selection, positive Evolution any more.

Thats something which can be just done by Eugenic properly in a modern postindustrial society, because natural selection, if implemented, leads just to contraselection under nowadays circumstances, and social policy without Eugenics as well.

Brain doesnt just grow, there need to be mutations and a selection for those mutants, that doesnt really happen atm.

Dr. Solar Wolff
Wednesday, July 14th, 2004, 05:14 AM
It would seem to me that as a species continues to evolve, after first emerging as a species, brain size would decrease. This is because survival skills would become almost involuntary responses, as birds have instincts. Birds have small brains yet they display complex behavior even compared to mammels. What may have happened is that behavior which once required thought became second nature to them. They became hard-wired for a certain behavior and didn't need such a large brain to think things over.