Archive for November, 2009
Darwin, in a letter to Asa Gray at Harvard University in September 1860, Darwin wrote that “embryology is to me by far the strongest single class of facts in favor” of the theory.
Just two months before the release of the first edition of The Origin of Species in September 1859, Darwin wrote to Charles Lyell, “Embryology in Chapter VIII is one of my strongest points I think.”
Writing in his autobiography, Darwin recalls: “Hardly any point gave me so much satisfaction when I was at work on the Origin, as the explanation of the wide difference in many classes between the embryo and the adult animal.”
Darwin’s premise was that the similarity between the structure and the embryo of animal and man was primary proof that man evolved from animals. In The Descent of Man, published in 1871, Darwin writes in the first chapter that embryology provides the “ample and conclusive evidence in favour of the principle of gradual evolution.”
Darwin was not an embryologist, and instead relied on the work of others. In The Origin of Species, Darwin gave credit to Ernst Haeckel: “Professor Haeckel in his “Generelle Morphologie” and in [other] works has recently brought his great knowledge and abilities to bear on what he calls phylogeny, or the lines of descent of all organic beings. In drawing up the several series he trusts chiefly to embryological characters [to establish evolutionary sequences].”
Based on what Darwin thought was scientific evidence concluded: “So again it is probable, from what we know of the embryos of mammals, birds, fishes, and reptiles, that these animals are the modified descendants of some ancient progenitor.”
In The Origin of Species, Darwin wrote, “Thus, as it seems to me, the leading facts in embryology, which are second to none in importance, are explained on the principles of variation in the many descendants from some … ancient progenitor”
During the twentieth-century, Haeckel’s embryos were prominently displayed in nearly every biology textbook, even though Haeckel eventually confessed that the drawings were fraudulent.
In January 1909, Haeckel’s confession was published as a letter in the Munchener Allegemeine Zeitung, an international weekly publication for the sciences, arts, and technology. In the letter, Haeckel clearly states that the drawings were contrived by “comparative synthesis” and not by accurate reproduction. Without the fraud, the expected evolutionary embryonic sequences had obvious gaps. Haeckel concedes, “a small portion of my embryo pictures (possibly 6 or 8 in a hundred) are really ‘falsified’.”
Even more sadly, Haeckel’s only defense was that fraudulent practices were an accepted practice even by some of the “most esteemed biologists” of the day. Haeckel wrote, “After this compromising confession of ‘forgery’ I should be obliged to consider myself condemned and annihilated if I had not the consolation of seeing side by side with me in the prisoner’s dock hundreds of fellow culprits, among them many of the most trusted observers and most esteemed biologists. The great majority of all the diagrams in the best biological textbooks, treatises, and journals would incur in the same degree the charge of ‘forgery,’ for all of them are inexact, and are more or less doctored, schematised, and constructed.” Indeed the scientific method had been abandoned not only by Darwin and Haeckel, but also by a large segment of the profession of biology.
Paul R. Ehrlich of Stanford University and author of the famous overpopulation book, The Population Bomb, wrote in 1963 that Haeckel’s law now only has a leading role in mythology—not in science. “This generalization was originally called the biogenetic law by Haeckel and is often stated as ‘ontogeny recapitulates phylogeny.’ This crude interpretation of embryological sequences will not stand close examination, however. Its shortcomings have been almost universally pointed out by modern authors, but the idea still has a prominent place in biological mythology.”
Like Haeckel’s embryo drawings, the history of evolution has been laced with an insidious legacy of fraud.
Darwin theorized natural selection to act through “slight, successive” changes -
“I do believe that natural selection will generally act very slowly, only over long periods of time…. natural selection acts slowly by accumulating slight, successive, favorable variations, it can produce no great or sudden modifications; it can act only by short and slow steps.”
While speculation on metabolic rates was beyond the scope of nineteenth century scientists, investigation in this field is now yielding new information on potential evolutionary correlates. During evolution, the continued increase in size and complexity, for example from “mouse-to-elephant”, was expected to follow corresponding “slight, successive” changes in basal metabolic rates in relationship to body mass.
The scientific team at The University of Birmingham in the United Kingdom headed by Craig White noted that the evolutionary “relationship between the basal metabolic rate (BMR) and body mass (M) of mammals has been at issue for almost seven decades.” BMR is a calculated number based on the equation BMR = aMb and the exponent b has long been disputed. The universality of exponent b is at the center of investigation.
To determine the exponent b, the researchers studied high-quality BMR data from 585 species and a subset of 537 species and published their findings in the October 2009 edition of Evolution* entitled “Phylogenetically informed analysis of the allometry of Mammalian Basal metabolic rate supports neither geometric nor quarter-power scaling”. The team results re-establish the fact that no evolutionary relationship exists between BMR and M concluding –
“Thus, we conclude that no single value of b adequately characterizes the allometric relationship between body mass and BMR.”
“Their results reinforce doubts as to the existence of a universal allometric relationship between mammalian BMR and body mass.”
Evidence for the natural law of evolution through “slight, successive” changes in the BMR, as expected from Darwin’s theory of natural selection simply does not exist. Species are unique—“kind after kind.”
Evolution. 2009 Oct;63(10):2658-67.
In 1943, published in a paper entitled “Mutations of Bacteria from Virus Sensitivity to Virus Resistance,” microbiologist Salvador Luria, biophysicist Max Delbrück, and bacteriologist and geneticist Alfred Hershey discovered that mutations occur at a constant rate. In 1969, they were awarded the Nobel Prize in Physiology and Medicine “for their discoveries concerning the replication mechanism and genetic structure of virus.”
The Luria-Delbrück Experiment opened the question, are mutations inherent to microbes for the purpose of adaption to rapidly changinging environments and not for evolution? While microbe resistance through mutation is a logical mechanism for evolution, the reality is the bacteria have remained a bacteria and the virus has remained a virus. Preexistent genetic variants determine the range of mutations. Pierre-Paul Grassé, president of the French Academy of Sciences, observed, “bacteria, the study of which has formed a great part of the foundation of genetics and molecular biology … stabilized a billion years ago.”
The question is whether the mutations are the “raw material for evolution” or nature’s means for the microbes to adapt to the environment. In a 2009 review article by entitled “Darwinian evolution in the light of genomics”, published in Nucleic Acid Research, Eugene V Koonin concluded, “There is no consistent tendency of evolution towards increased genomic complexity” through mutation as expected with current evolutionary theories. Mechanisms of evolution remain beyond any known natural law.
Reflecting on the role of mutations, Grassé questioned, “What is the use of their unceasing mutations if they do not change?” Grassé concludes, “the mutations of bacteria and viruses are merely hereditary fluctuations around a median position; a swing to the right, a swing to the left, but no final evolutionary effect.” Microbes undergo constant mutations, but do not evolve – mutation stasis.
*Nucleic Acids Res. 2009 March; 37(4): 1011–1034
Pangenesis was Darwin’s hypothetical mechanism for the origin of variation and inheritance through particles called gemmules. This “provisional hypothesis” on the origin of variation was presented in his 1868 work The Variation of Animals and Plants under Domestication through gemmules acquiring new variations that brings “together a multitude of facts which are at present left disconnected by any efficient cause”.
The etymology of pangenesis comes from the Greek words pan (a prefix meaning “whole”, “encompassing”) and genesis (birth) or genos (origin). Gemmules were thought to learn from experiences.
The origin of new variations was critical for Darwin’s theory since the “slight, successive” changes in evolution requires a constant stream of new variations for the actions of natural selection. Gemmules were imagined particles. These learned gemmules particles sent from every cell (pan) in the body with new variations (genos) accumulated in the germ cells and had a ‘vote’ in the constitution of the offspring (genesis).
This hypothesis provided a possible mechanism for the inheritance of acquired characteristics, as proposed by Jean-Baptiste Lamarck, which Darwin believed to be the origin of new variations in living organisms.
Little did Darwin know that even before the publication of the fourth edition of The Origin of Species in 1866, Gregor Mendel had presented the now-famous paper entitled “Experiments on Plant Hybridization,” laying the foundations of modern genetics.
Although, Mendel’s discovery went unnoticed until the turn of the twentieth century, German biologist August Weismann, at the University of Freiburg, launched the first scientific evidence directly challenging Darwin’s theory. Now known as the “Weisman Barrier,” in 1883, Weismann cut off the tails of mice from 21 generations. Seeing that the 22nd generation still had tails, Weismann concluded that the evidence contradicted Darwin’s theory of pangenesis despite obvious reasons for change in the mice, “continuity” was observed, not new variations.
Ernst Mayr, Darwin’s twentieth-century bull-dag, stated Weismann as “The second most notable evolutionary theorist of the 19th century.” What is still unresolved now 150 years later is—what is the origin of variation?