The Driving Forces of Evolution

Genetic Processes in Populations

David Wool

• Éditeur: CRC Press
• Année: 2006
• ISBN:
  9781000737998
• Édition: 1
• Sujet: Sciences biologiques
• Sous-sujet: Génétique et génomique

To cope with the abiotic stress-induced osmotic problems, plants adapt by either increasing uptake of inorganic ions from the external solution, or by de novo synthesis of organic compatible solutes acting as osmolytes. Of the osmoregulants and protectants discussed in this volume, trehalose, fructans, ectoine and citrulline, which are generated in

PART I

Mainly Theory

Chapter 1: The Beginning

Chapter 2: Evolution as an On-going Process

Chapter 3: Populations at Equilibrium: The Hardy-Weinberg Law

Chapter 4: Deviation from Equilibrium: Genetic Drift – Random Changes in Small Populations

Chapter 5: Deviations from Equilibrium: Mutations

Chapter 6: Deviations from Equilibrium: Migration

Chapter 7: Deviations from Equilibrium: Non-random Mating

Chapter 8: Deviation from Equilibrium: Selection

CHAPTER 1

The Beginning

Is evolution a theory, a system, or a hypothesis? It is much more: it is a general postulate to which all theories, all hypotheses, all systems must satisfy in order to be thinkable and true. Evolution is a light which illuminates all facts, a trajectory which all lines of thought must follow. (Teilhard de Chardin, cited by Dobzhansky, 1961, p. 347)

Evolution, as a scientific discipline, comprises three main fields of research: 1) The origin of life, 2) Evolution as the description of the history of the biological world (the lines of descent connecting different groups of organisms), and 3) Evolution as an ongoing process. I shall deal with the first subject briefly in this chapter. Most of the material in the book deals with the third. The second subject (phylogeny) is deferred to the end of the book.

THE POINT OF DEPARTURE

The starting point of evolution as a science is the conviction that the biological world as we know it has evolved, gradually and slowly, from non-living matter.

There are those who, even today, do not accept this starting point, and believe that animals and plants were created by the Deity in six days, as written in the first chapter of Genesis. Such ‘creationists’ objected to the theory of evolution from the start, and continue to do so today. In some states of the USA, demands to remove evolution from the school curriculum, or alternatively, demanding ‘equal time’ for ‘creation science’ as an equivalent scientific theory to evolution, are brought up periodically. The dispute has recently (2004) entered the pages of the oldest, prestigious scientific journal, Nature. In an editorial (Nature 434: 1053) it was suggested that scientists should try to convince creationist readers that their belief can be reconciled with science, and that the journal should not reject creationist papers out of hand as unscientific (ironically, Nature was co-founded in 1869 by T.H. Huxley, a self-declared agnostic who fought fiercely against religious dogma!). The editorial evoked angry responses from many scientists.

Creationism is not a scientific equivalent to the theory of evolution. Creationists believe that the world was created and is controlled by the external power of the Deity, and, as such, the laws which regulate the world are beyond the grasp of the human mind. Scientists seek answers for questions about nature by studying nature itself, and derive explanations and suggest rules for its regulation from observations and experiments, not from external forces. The dispute between creationists and scientists is not about evolution: it is about the belief in God. There are no scientific tools to deal with matters of belief.

The ‘proofs’ and arguments brought forward by creationists to support their belief are not new. The same arguments and examples were published two hundred years ago by the British theologian, William Paley, in his book ‘Natural Theology’ (1802) (In fact, Paley seems to have had a much better knowledge of biology than some of the present-day creationists). The main argument is that complex structures like the human eye, so beautifully adjusted for its function as an organ of vision, could not have been formed by chance: it seems that the eye – and organs like it – were designed for the function they perform, and where there is a design – there must be a designer (‘intelligent designer’ (ID) is the most recent catch phrase for creationism). But presenting evolution as a matter of chance is wrong and misleading. Evolutionists claim that the structures were formed not by chance, but rather by the gradual accumulation of improvements from simple structures, which then survived because they had given some advantage to individuals over the carriers of simpler structures.

Among evolutionists, there is a diversity of opinions regarding some mechanisms of evolution (e.g., the importance of selection versus random processes, or whether evolution has been gradual or ‘saltational’). The theory of evolution has evolved over the years, with changes in emphasis about such matters as the lines of descent among some groups of species (even the concept of a ‘species’ has been controversial). But all these approaches are disputes among scientific theories, starting from the same point of departure – and considering natural processes only. Creationism is not a scientific theory because it allows control by external forces, and it cannot be an alternative to the theory of evolution. As one of the greatest British scientists, ‘the father of Geology’, Charles Lyell – wrote in the early 19th century:

“For what we term “independent creation” or the direct intervention of the Supreme Cause, must simply be considered as an avowal that we deem the question to lie beyond the domain of science” (Lyell, 1873, “The Antiquity of Man. p. 468)

THE ORIGIN OF LIFE

Where? It is assumed almost universally among evolutionists that life began on planet Earth, at a remote time when conditions were suitable. Some, h...