5 de setembro de 2009

Evolução e condicionalismos químicos


Resumo da conferência do Prof. José Fraústo da Silva no Congresso sobre O Impacto de Drawin

Reevaluating the Origin of Species: the chemical constraints of evolution


After a short digression on the contribution of Charles Darwin (and some colleagues) to the ideas on the evolution of species, on the work of other naturalists that predated them, and on the advances of scientists in the XIX and XX centuries, originating what is usually called neo-Darwinism, this lecture will be centered on the main factors necessary for life - raw materials, available energy and functional instructions (information) – focused specially on the role of the chemical elements (and their compounds) initially provided by the environment and later by other living organisms, that takes us to other questions, such as symbiosis, synergism and delegation of functions, leading to the conclusion that it is the ecosystem that determines and manages the evolution, not random mutations in individual organisms or species.
Life seems to have emerged in our planet some 3,5 – 3,8 billion years ago, when the atmospheric environment was essentially reductive and there was no free oxygen (O2) in appreciable concentration since this element, due to its reactivity, was largely combined with hydrogen (as H2O) and several other elements, such as carbon, phosphorous, silicon, aluminium, calcium, etc. but not with transition metals, that for low levels of O2 tend to form sparingly soluble sulfides. This situation changed considerably with the progressive oxidation of the environment; some metals (Zn, Cu, Mo and others) became more available and other elements less available (e.g. Fe and S) How did these changes affect the life on Earth?
To follow a systematic sequence in the description we will consider first and in more detail the raw-materials, then the driving force, energy, and some thermodynamic concepts which is our view and of a few other authors have not been correctly interpreted when applied to biological systems, and finally information, an essential requirement which again is frequently misinterpreted and usually limited to a dominant role of coded DNA.
Along the lecture some other important questions will be mentioned, such as confinement, synergism, symbiosis, changes in the environment and what we have called the “second code”, the brain, whose self-conscious character in the human beings led to our most recent differentiated “chemotype” – the modern humans. Together, all of these aspects lead to a conclusion: it is, in effect, the ecosystem that evolves.
A more detailed description of our work is given in the bibliography and in the references of our books and papers.

References:
Corning Peter, Holistic Darwinism, The University of Chicago Press , 2005
Id., Nature’s Magic, Cambridge University Press ,2003
Fraústo da Silva, J.J.R & Williams, R.J.P., The biochemical chemistry of the elements, Oxford University Press, 1st. edition 1991, 2nd, revised edition 2001.
Id., The natural selection of the chemical elements, Oxford University Press, 1996.
Id., Bringing chemistry to life – from matter to man, Oxford University Press, 1999.
Id., The chemistry of evolution – the development of our ecosystem, Elsevier, 2007.
Id., “The systems approach to evolution” in Biochem.Biophys.Research. Comm. 297, 689-699 2002),
Id., “Evolution was chemically constrained” in J. Theor. Biology, 220, 323-343 (2003) Id., “Evolution revisited by inorganic chemists” in Fitness of the Cosmos for Life, Cambridge Univ. Press, 2008.
Fraústo da Silva, J.J.R. “The evolution of chemotypes” in Molecular and Supramolecular Bioinorganic Chemistry, Nova Science, U.S.A. 2009.
McCalman, Ian, Darwins’s Armada, Simon & Schuster UK Ltd., 2009