Saturday, March 18, 2006
On tuesday Waddington's "The Evolution of adaptations" (link goes to the paper itself) appeared on the Main Blog and since then 3 commentaries have been added to the Personal Posts category:
The reigning modern view is that, in nature, the direction of mutational change is entirely at random, and that adaptation results solely from the natural selection of mutations which happen to give rise to individuals with suitable characteristics. I want to argue that this theory is an extremist one
Brief comments on the intellectual strategy used to reduce an initially 'incredible' possibility (derived from the above quote) to a far more 'credible' one.
Describes how ostrich callosities could have become hereditary from the perspective of the proposed internal evolutionary mechanism.
Waddington only refers to the callosities found "fore and aft" on the underside of the body.
The ostrich also has callosities on the ankle and the proposed mechanism shows why these have 'persisted' even though they "are of no use" (further indicating the proposed mechanism has no connection with such outmoded concepts as "The Law of Use and Disuse).
Friday, March 17, 2006
A Look at Bogus "History" in SchoolbooksMichael T. Ghiselin
Jean-Baptiste de Lamarck (1744-1829) takes a prominent place in many biology textbooks and life-science textbooks, which depict him as the author of a "theory" of evolution based upon the inheritance of acquired characteristics. Lamarck's views, these books say, should be rejected in favor of the theory of evolution by natural selection, propounded by Charles Darwin (1809-1882), because only Darwin's theory is compatible with the findings of 20th-century genetics.
The Lamarck presented in schoolbooks, however, is a fiction -- an imaginary figure who has been fashioned from hearsay and wrong guesses, and who has been replicated in countless books by successive teams of plagiarists. This figure shares very little, except his name, with the Lamarck of history. Textbook-writers have imbued the fictitious Lamarck with an importance that the real Lamarck never had, and they have credited him with ideas that the real Lamarck did not hold. They also have invented a myth in which those ideas are compared falsely with Darwin's ideas, to produce a bogus dichotomy.
Textbooks typically introduce Lamarck with a flourish, as in this passage from Prentice Hall's Biology: The Study of Life:
One of the first theories of evolution was presented by the French biologist Jean Baptiste de Lamarck in 1809. From his studies of animals, Lamarck became convinced that species were not constant. Instead, he believed that they evolved from preexisting species. . . . According to Lamarck's theory, evolution involved two principles. He called his first principle the law of use and disuse. . . . The second part of Lamarck's theory was the inheritance of acquired characteristics. Lamarck assumed that the characteristics an organism developed through use and disuse could be passed on to its offspring.
Much the same material appears in Holt's Biology Today:
In 1809 a French biologist named Jean Baptiste de Lamarck presented an explanation of the origin of species in his work Zoological Philosophy. Lamarck developed a theory of evolution based on his belief in two biological processes:
1) The use and disuse of organs. According to Lamarck, organisms respond to changes in their environment by developing new organs or changing the structure and function of old organs. . . .
2) Inheritance of acquired traits. Lamarck believed that acquired characteristics were passed on to the organism's offspring....
Such claims give many false or misleading impressions, starting with the implication that Lamarck's views were original.
Thursday, March 16, 2006
Paper Title: Darwinism Design and Purpose: A European Perspective
Author: Jean Staune
Institutional Affiliation: General Secretary, Université Interdiciplinare de Paris
(This paper was prepared for "Science and Religion: Global Perspectives" June 4-8,
2005, in Philedelphia, PA, USA , a program of the Metanexus Institute
In the USA 'Issues in Biology and Religion' usually implies a debate between neo- Darwinians and Creationists or, more recently, the Intelligent Design movement. In Europe, however, the situation is somewhat different since no one really believes in creationism anymore and Intelligent Design is unheard of. Consequently the debate is completely different. It is a debate between evolutionists. The first debate is between 'Classical Darwinians' and scientists like Christian de Duve (Belgian Nobel Laureate for Medicine) or Simon Conway Morris (UK Paleontologist based at Cambridge) and is about the reproducibility of evolution. Presenting an alternative view from Gould for whom contingence rules supreme in the processes of evolution, de Duve and Conway Morris postulate that if you 'run' evolution again on a planet with more-or-less the same conditions as you find on Earth the result will be more-or-less the same. More specifically it will lead to intelligent beings that resemble us. They accept that there are no other forces that act on evolution than Darwinian mechanisms (random mutations and natural selection) but they show evidence that chance is channeled by the laws of nature. If you play dice for a very long time you can be sure that a very special result will certainly occur.
The second debate is between classical neo-Darwinians and non-Darwinians i.e. scientists that claim that Darwinian mechanisms are not the main forces driving evolution. There are in France, Italy and England two main schools of thinking in this area. One believes that there is a goal in the process of evolution and so randomness is just apparent, not real, in the mechanism of evolution. At a much deeper level evolution is more or less predictable because it has a purpose. The other supports the idea of self-organization, autopoeisis and emergence. For them these concepts are just as important, if not more important than Darwinian concepts in our understanding of evolution. In our first part we will describe these debates and the main scientists whose positions differ from the classical non-Darwinian one, but who are, WITHOUT EXCEPTION, evolutionists. It is of special interest for an American audience because it will show how the debate is much wider in this field than the narrow controversies between Darwinians on one hand and 'crazy creationists' or the proponents of Intelligent Design on the other.
It could be very surprising and interesting for an American audience to discover that there are non-Darwinian scientists who claim they support evolution more strongly than Darwinians! The reason is epistemological: Teilhard supporters who form the majority of non-Darwinian scientists in Europe, claim that the existence of purpose and directionality is better evidence for the reality of evolution than any demonstration using Darwinian concepts.
To conclude we will ask a question of a scientific and epistemological nature, namely: is there a way of applying, in evolutionary biology, the concepts that have appeared in other areas or research and which show the limitations of our capacity to understand reality e.g. Heisenberg's uncertainty principle or Godel's theorem of incompleteness? If so then what concept of evolution can this lead us to?
Wednesday, March 15, 2006
Evolution Of Morphological Integration: Developmental Accommodation Of Stress-induced Variation
1) Press Release
Stress is a major factor in evolution, but for stress-induced modifications to have evolutionary importance they have to be inherited and persist in a sufficient number of individuals within a population. This requires an organism to survive stress and reproduce at least once; thus stress-induced variation has to be accommodated by an organism without much reduction in its functionality. How is such accommodation accomplished?
In an article in the September issue of The American Naturalist, Alexander V. Badyaev (University of Arizona) and colleagues show that complexity and cohesiveness of foraging structures of shrews enables accommodation of stress-induced developmental abnormalities in individual components of morphological complexes. Such developmental compensation and accommodation not only allow shrews growing under stressful environments to maintain locally adaptive foraging morphology, but also provide a mechanism for stress-induced evolutionary change.
Full text here
[Badyaev et al, The American Naturalist, Sept '05]
Extreme environmental change during growth often results in an increase in developmental abnormalities in the morphology of an organism. The evolutionary significance of such stress-induced variation depends on the recurrence of a stressor and on the degree to which developmental errors can be accommodated by an organism's ontogeny without significant loss of function. We subjected populations of four species of soricid shrews to an extreme environment during growth and measured changes in the patterns of integration and accommodation of stress-induced developmental errors in a complex of mandibular traits. Adults that grew under an extreme environment had lower integration of morphological variation among mandibular traits and highly elevated fluctuating asymmetry in these traits, compared to individuals that grew under the control conditions. However, traits differed strongly in the magnitude of response to a stressor--traits within attachments of the same muscle (functionally integrated traits) had lower response and changed their integration less than other traits. Cohesiveness in functionally integrated complexes of traits under stress was maintained by close covariation of their developmental variation. Such developmental accommodation of stress-induced variation might enable the individual's functioning and persistence under extreme environmental conditions and thus provides a link between individual adaptation to stress and the evolution of stress resistance.
Full text at:
Tuesday, March 14, 2006
Endeavour 134-139 (July 1953)
The evolution of adaptations
C. H. WADDINGTON
Current biological belief regards evolution as being primarily the result of the natural selection of random mutations, useful adaptations gradually spreading throughout a race. Professor Waddington regards this as an 'extreme view, and in this article puts forward a hypothesis to explain how acquired characteristics may become hereditarily fixed by a process of genetic assimilation not invoking the generally discredited theory of direct inheritance.
It is abundantly found in the living world that the structure of an animal or plant is very precisely adapted to the functions which it has to perform. The nature of the processes by which this situation has been brought about during evolution provides one of the major problems for biological theory. The hypothesis of the inheritance of acquired characters suggested that in some way or other the effects of functioning become themselves inherited. It has usually been interpreted to mean that the reaction between the organism and its surroundings has, as one of its results, an effect on the germ-plasm such that new hereditary changes occur, of a kind which determines the development in later generations of individuals suited to these particular conditions of life. Although this idea has recently been revived in a rather nebulous form in the Soviet Union, it has been so completely rejected by the rest of the scientific world that it is hardly considered to be worthy of discussion in most of the important recent works on evolution. The reigning modern view is that, in nature, the direction of mutational change is entirely at random, and that adaptation results solely from the natural selection of mutations which happen to give rise to individuals with suitable characteristics. I want to argue that this theory is an extremist one, and that, in essaying to account for adaptation, it neglects to call to its aid the doctrines emerging in other fields of modern biology which can quite properly be combined with the conclusions of genetics in the strict sense. In the discussion which follows, attention will be confined to animals, but there is no reason to doubt that similar arguments could be advanced in the botanical field.
It will be advisable first to glance briefly at the phenomena which are usually referred to under the heading of adaptation, since they are of several different kinds which must be distinguished from one another.
Common objections to 'Internal Evolutionary Mechanisms' (2)
5) Internal Mechanisms are 'directional' (objections 1 to 4 are here)The mathematical model currently used is very basic so an explanation of why the proposed homeostatic internal evolutionary mechanism isn't 'directional' has initially been posted to the Personal Posts category:
"An Internal Evolutionary Mechanism and 'Direction in Evolution': Preliminary Notes"
Monday, March 13, 2006
[Pigliucci & Kaplan, Trends in Ecology and Evolution, '00]
"Twenty years have passed since Gould and Lewontin published their critique of 'the adaptationist program' - the tendency of some evolutionary biologists to assume, rather than demonstrate, the operation of natural selection. After the 'Spandrels paper', evolutionists were more careful about producing just-so stories based on selection, and paid more attention to a panoply of other processes. Then came reactions against the excesses of the anti-adaptationist movement, which ranged from a complete dismissal of Gould and Lewontin's contribution to a positive call to overcome the problems. We now have an excellent opportunity for finally affirming a more balanced and pluralistic approach to the study of evolutionary biology."
""The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme"
STEPHEN JAY GOULD AND RICHARD C. LEWONTIN
An adaptationist programme has dominated evolutionary thought in england and the united states during the past forty years. It is based on faith in the power of natural selection as an optimizing agent. It proceeds by breaking an organism into unitary 'traits' and proposing an adaptive story for each considered separately...
Sunday, March 12, 2006
[Lenski & Sniegowski, Annual Review of Systematics, Nov '95]
A central tenet of evolutionary theory is that mutation is random with respect to its adaptive consequences for individual organisms; that is, the production of variation precedes and does not cause adaptation. Several recent experimental reports have challenged this tenet by suggesting that bacteria (and yeast) ''may have mechanisms for choosing which mutations will occur'' (6, p. 142). The phenomenon of nonrandom mutation claimed in these experiments was initially called ''directed mutation'' but has undergone several name changes during its brief and controversial history. The directed mutation hypothesis has not fared well; many examples of apparently directed mutation have been rejected in favor of more conventional explanations, and several reviews questioning the validity of directed mutation have appeared (53, 54, 59-61, 79, 80). Nonetheless, directed mutation has recently been reincarnated under the confusing label ''adaptive mutation'' (5, 23, 24, 27, 35, 74). Here we discuss the many experimental and conceptual problems with directed/adaptive mutation, and we argue that the most plausible molecular models proposed to explain ''adaptive mutation'' are entirely consistent with the modern Darwinian concept of adaptation by natural selection on randomly occurring variation.
In the concluding section of the paper, we discuss the importance of an informed evolutionary approach in the study of the potential adaptive significance of mutational phenomena. Knowledge of the molecular bases of mutation is increasing rapidly, but rigorous evolutionary understanding lags behind. We note that ascribing adaptive significance to mutational phenomena (for example, ''adaptive mutation'') is beset with some of the same difficulties as ascribing adaptive significance to features of whole organisms (29). We consider some examples of mutational phenomena along with possible adaptive and nonadaptive explanations. [Evolution]
Phenotypic integration: studying the ecology and evolution of complex phenotypes (Ecology Letters)
Volume 6 Page 265 - March 2003
Volume 6 Issue 3
Phenotypic integration refers to the study of complex patterns of covariation among functionally related traits in a given organism. It has been investigated throughout the 20th century, but has only recently risen to the forefront of evolutionary ecological research. In this essay, I identify the reasons for this late flourishing of studies on integration, and discuss some of the major areas of current endeavour: the interplay of adaptation and constraints, the genetic and molecular bases of integration, the role of phenotypic plasticity, macroevolutionary studies of integration, and statistical and conceptual issues in the study of the evolution of complex phenotypes. I then conclude with a brief discussion of what I see as the major future directions of research on phenotypic integration and how they relate to our more general quest for the understanding of phenotypic evolution within the neo-Darwinian framework. I suggest that studying integration provides a particularly stimulating and truly interdisciplinary convergence of researchers from fields as disparate as molecular genetics, developmental biology, evolutionary ecology, palaeontology and even philosophy of science.
Full text at: