The Plasticity of Sphenoid

The film of Thomas Johnson "Homo Sapiens, a new history of the man" remarkably shows how the discovery of Anne Dambricourt concerning the cranio-facial contraction (CFC) or successive inflections of the sphenoid from the Prosimien to Homo Sapiens signs an evolutionary process stabilized and iterative since sixty million years. An important fact: this process is based on an internal dynamics - the plasticity of the sphenoid - which has a crucial role in the development of the human cranium and the installation of the skeleton as of the embryonic stage. This complex bone located at the level of the average stage of the base of the cranium indeed presented 5 successive inflections (or CFC stages) since 60ma, always directed in the same direction, accelerating considerably since the Australopithecus (6ma) until the homo kind (2ma) and Sapiens (160000ans) [ 1 ] and predicting a possible "Homo Futuris". Concomitant work of the orthodontist Marie-Josèphe Deshayes arrives at the same conclusions, attesting important modifications of the maxillaries causing dental disharmonies jaw in the young children of a great part of the current population.

These observations lead us to another vision of the human evolution contradicting the dominant theory of the savane [2 ], which defines the adaptation to the medium like the only engine of the evolution. It is however not anti-darwinist, as some inevitable polemics hear it, in the direction where it is not opposed of anything to the natural selection and the role of genetics or environment. It brings on the contrary complementary elements to reconstitute the puzzle of the evolution by revealing an "inside story" [ 3 ] where only prevailed the East side story, according to the terms of the biologist Jean Chaline. Elements which can be interpreted differently according to authors, could imply specific genes of regulation [4 ] and prospects for better understanding of the phylo- and ontogenesis, the appearance of the bipedy or the articulated language.

In short, this film has the merit to show to a general public that another vision of the evolution of the man, shared by many scientists is possible. A vision which does not claim to hold the truth, but which has the merit to be based on objective measures and to put forth the assumption that there is probably not only one engine of the evolution. Of course, like all new theory, rejections and enthusiasms will mark out its course, but only a transdisciplinary attitude [5] will permit to archaeologists and paleo-anthropologists to evaluate it with serenity. Whatever the form that it take, nobody can remain indifferent in front of the philosophical questions raised by this film since that it touch human identity.

Comment from M-W DeBono

[ 1 ] According Anne Dambricourt’s work.

[ 2 ] Already discussed by the recent discovery of many fossils as Professor Tobias in film indicates it clearly.

[ 3 ] I.e. an internal evolutionary process : cellular and subcellular...

[ 4 ] The genome of the chimpanzee has been just published in Nature and researches are made to compare the genomic sequences of the chimpanzee with other primates and to the man.

[ 5 ] Attitude that we have developed within PSA for several years and which is perfectly illustrated in this evolutionary approach where palaeontology addresses as much to biology as with modelling, the dynamics of the nonlinear systems, the embryology, experimental medicine etc... all these disciplines being crossed by a common prospect: the comprehension of this new assumption of the evolution human and tending to going beyond their own disciplinary fields as of their contradictions - as subjects - to reach a new side of the knowledge of which each one will profit.