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Explore the historical debate around embryology and vestigial organs in evolution theory, including the contributions of Darwin and Ernst Haeckel. Understand the theory of embryological recapitulation and the controversies surrounding Haeckel's fraudulent embryo drawings.
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Arguments of evolution in biology textbooks—EMBRyology and Vestigial organs Suzanne Phillips Loma Linda University
Darwin and embryology • Darwin observed certain similarities in the early stages of the development of vertebrate animal embryos. • He stated that "embryos of different species within the same class in general, but not universally, resemble each other." (1859) • In his view, this observation established two things: • Darwin thought that the embryos of modern vertebrates are similar because they have evolved from an ancestral form that had adult characteristics now observed in the embryos of modern vertebrates. • It provided proof that all animals are derived from a single common ancestor.
In addition, Darwin thought that the characteristics observed in modern embryos of vertebrates show how they could have been the ancestors of those organisms.
Ernst Haeckel • The embryologist Ernst Haeckel was a naturalist, philosopher, teacher and German artist. • He discovered, described and named thousands of new species, built a family tree relating all life forms, and coined many terms in biology, including anthropogenesis, ecology, phylum, phylogeny, stem cells and Protista. • Haeckel promoted and popularized the work of Charles Darwin in Germany. • He made a set of drawings depicting the embryos of various vertebrate classes in their early stages of development. • He formulated the famous biogenic law, and developed the controversial theory of recapitulation.
Theory of embryological recapitulation • According to Haeckel, ontogeny recapitulates phylogeny: • During ontogeny (embryological development), each individual embryo recapitulates all previous stages of evolution (phylogeny). • Vertebrate embryos show a synthesis of the successive stages of evolution.
According to Haeckel, embryos are very similar at every stage of development. This suggests a recapitulation of the evolutionary process. In addition, this suggests that each class, reading from left to right, is a more complex step than the previous one. Darwin thought this evidence was the most solid kind of evidence in favor of his theory of Common Ancestor.
is the theory of recapitulation valid? • Modern embryologists do not believe in embryological recapitulation. • Although most neo-Darwinists still accept that early embryological similarities point to common ancestry, they no longer think that embryos reveal the adult form of their evolutionary ancestors. • However, biology textbooks still include it as an argument for evolution. • Where are the flaws?
the Reality Haeckel’s model Reality ≠
Photographs of the real stages of embryological development.(From Meyer, S. C., S. Minnich, J. Moneymaker, P. A. Nelson, and R. Seelke. 2007. Explore evolution. The arguments for and against neo-Darwinism. Hill House Publishers, Melbourne.)
Photographs of the real stages of embryological development.(From Meyer, S. C., S. Minnich, J. Moneymaker, P. A. Nelson, and R. Seelke. 2007. Explore evolution. The arguments for and against neo-Darwinism. Hill House Publishers, Melbourne.)
haeckel’s fraud • "Everything that has been quoted against the theory was already known when the theory was presented. Nevertheless, it was widely accepted" (Kerkut 1960). • Counterfeiting was already known in the time of Haeckel, in the 1860s. • Haeckel falsified some of his embryo drawings to support his theory. • He used the same sketches to represent several different animals. • He was accused of altering embryo drawings made by others. • For his falsification, he was condemned by a German court. • Significant reports of the frauds and falsifications date from 1908, 1875 and already in 1868. • Their forgeries were detailed in 1915 in a book by Assmuth and Hull titled, Haeckel Frauds and Counterfeits.
EXAMPLES OF THE HAECKEL’S FORGERIES Original Haeckel’s forgeries
very different embryos • In 1894, Adam Sedgwick, an embryologist at the University of Cambridge, challenged Darwin's two statements: • That vertebrate embryos were more similar than vertebrate adults. • That the younger the embryos, the greater the resemblance.
He realized that even the embryos of closely related organisms, such as two species of birds, looked very different in the early stages of development. • The same was known for distantly related organisms, such as birds and fish. • Sedgwick claimed that every embryologist of his time—in 1894—knew it. • If the embryologists knew that the claims of Darwin and Haeckel were false, why did the biogenic law and the idea of recapitulation prevail? • They are still found in textbooks today.
One reason was that no one paid attention to the publications of embryologists such as Sedgwick amidst the popularity of Darwin's evolutionary theory and Haeckel's inaccurate drawings. • Finally, erroneous statements were introduced in the Encyclopaedia Britannica, and remain in many modern textbooks. • The images were manipulated and the facts distorted. • But some prestigious scientists have denounced that, including the famous paleontologist Stephen Jay Gould (2000) of Harvard University, • "I think we have the right to be astonished and ashamed for a whole century of meaningless recycling that has led to the persistence of these drawings in large numbers, if not most, of modern textbooks."
In 1915, Assmuth and Hull wrote: • "One can hardly find a prominent scientist who accepts this law as outlined, and the reason for this is quite convincing, that recent research has clearly demonstrated that the exceptions to this law are much more frequent than their materializations. The individual embryos of different animals do not correspond predominantly with gradations which, according to the theory of evolution, constitute the history of the development of life. “
evolution does not explain embryology • Sir Gavin de Beer (1899-1972), British zoologist and director of the British Museum of Natural History, rejected the concept of embryological recapitulation. • He affirmed that "evolution does not explain embryology" (p.173). • He found numerous flaws in the evolutionary argument of embryology. • It was assumed that evolution had created teeth before the tongue, but humans develop the tongue before the teeth. • Vertebrate embryos develop the heart before the rest of the circulatory system, but the theory of evolution supposes the opposite.
haeckel’s fraud • Michael K. Richardson, a professor and embryologist at the School of Medicine at St. George's Hospital in London, has exposed this fraud in an article in the journal Anatomy and Embryology (1977). • Richardson says that he always thought Haeckel's drawings were wrong, "because they do not fit with his knowledge of the rates at which fish, reptiles, birds and mammals develop their distinctive characters."
Richardson assembled an international team to examine and photograph "the external shape of the embryos of a wide range of vertebrate species, comparable to that of one of Haeckel's stages." • The team collected embryos from 39 different animals, including among others, marsupials from Australia, tree frogs from Puerto Rico, snakes from France and a crocodile embryo from England. • They found that embryos of different species are very different. • In fact, they are so different that Haeckel's drawings (similar embryos of humans, rabbits, salamanders, fish, chickens, etc.) could not have arisen from actual samples.
"This is one of the worst cases of scientific fraud. It is scandalous to find someone who has been considered as a great scientist who has deliberately deceived me. It upsets me... What [Haeckel] did was to take a human embryo and copy it, pretending that the salamander, the pig and all the others were the same in the same state of development. They are not ... It's counterfeit. " • Haeckel not only changed the drawings to add, omit and change characteristics, but, according to Richardson and his team, "also manipulated the scale to exaggerate the similarities between species, even though the differences in size were ten times greater."
other problems of the theory of recapitulation • The detailed study of the embryos indicates that the embryological development of the animals is much more complex than the theory of recapitulation suggests. • No more complex embryo develops along the same path as assumed for evolution from a common ancestor. • There are too many exceptions to the postulated pattern. • In fact, many structures are developed in an succession that is the opposite of evolution.
embryology—the persistence of the argument • Despite the numerous voices indicating the errors of recapitulation theory and the lack of evidence from embryology for evolution, some scientists still argue in favor of the standard evolutionary interpretation of embryology. • Eugenie Scott of the National Center for Scientific Education defends the use of these (and other defective evolutionary tests) in textbooks because they "clearly communicate these basic concepts to uninformed students." (Scott 2001)
Photographs of the real stages of embryological development.(From Meyer, S. C., S. Minnich, J. Moneymaker, P. A. Nelson, and R. Seelke. 2007. Explore evolution. The arguments for and against neo-Darwinism. Hill House Publishers, Melbourne.)
Other scientists argue that the early stages of embryos in some species seem different because those stages have undergone modifications to adjust to environmental conditions. • Darwin already suggested this in the fourth edition of his book The Origin of Species. • According to this explanation, the Darwinian theory explains both embryonic similarity and dissimilarity. • Therefore, the theory of evolution explains anything, and the idea of descent of a common ancestor is consistent with anything we observe in embryos.
Neo-Darwinists argue that a combination of similarity and dissimilarity is what one would expect if species, in fact, descended with modifications from a common ancestor. • But critics argue that • A theory that explains everything, present or absent, cannot be proven. • The theory of evolution cannot explain why similarity and dissimilarity occur without resorting to the assumption that evolution actually occurred—the theory of evolution assumes that evolution occurs. • The embryology argument is circular: the supposed similarity of the embryos points to a common ancestor and the fact that organisms descend from a common ancestor explains why there are similarities and dissimilarities in embryos of different species.
Fish embryo:The gills are developed in this region. But in mammals:They never form slits and are never part of the respiratory system.These folds are transformed into other organs. GILL SLITS • The most common evidence to support embryological recapitulation is the presence of so-called "gill slits" in the embryos of fish, mammals and humans at a particular stage of development. • They supposedly show that humans and other animals evolved from an ancestral fish. • It is true that the embryos of these animals have a series of folds in the tissue of the cervical region.
sources ad references • Assmuth J, Hull ER. 1915. Haeckel's frauds and forgeries. Bombay, India: Examiner Press. 104 pp. • Darwin, Charles. 1859. On the Origin of Species. Cambridge, Massachusetts [Facsimile of the First Edition], Harvard University Press, 1964, chapter 13: 442. • de Beer G. 1958. Embryos and ancestors. London: Oxford University Press. • Gould, S. J. 2000. Abscheulich! (Atrocious!). Natural History 109(2):42. • Kerkut, G. A. 1960. Implications of evolution. New York, Pergamon Press, p.66. • Langman, J. 1981. Medical embryology, 4th edition, Williams & Wilkins, Baltimore, p.268. • Meyer, S. C., S. Minnich, J. Moneymaker, P. A. Nelson, and R. Seelke. 2007. Explore evolution. The arguments for and against neo-Darwinism. Hill House Publishers, Melbourne. • Richardson, M. K., J. Hanken, M. L. Gooneratne, C. Pieau, A. Raynaud, L. Selwood, and G. M. Wright. 1997. There is no highly conserved embryonic stage in the vertebrates: implications for current theories of evolution and development. Anatomy and Embryology 196(2):91-106 • Scott, E. C. 2001. Fatally flawed iconoclasm. Science 292(5525):2257a. • Thompson, W. R. Introduction to Charles Darwin’s Origin of Species, 6th edition (1872). Dutton and company, New York.
DEFINITION OF VESTIGIAL ORGANS: • Organs or structures thought to have been better developed and functional function in the past but to have now lost most or all of their role and/or structure. • They were useful in ancestral species but have been abandoned in modern animals.
Robert Wiedersheim (1895) listed 180 alleged rudimentary organs. • Biologists now agree that there are only a handful of them. • Some scientist believe there none.
SOME ALLEGED VESTIGIAL ORGANS • 2014 paper in “Evolution”: the pelvic bones of whales are “one of the classic examples of a vestigial structure,” said [authors]. “But what we found was that the shapes of these bones are highly associated with the mating systems of these whales and dolphins — species that are more promiscuous have more-complex-shaped pelves.”
Coccyx Lowest part of the vertebral column. Also called tail bone. Normally made up of two to five segments, with joints between them. Attached by ligaments to the margins of the sacral hiatus. Evolutionists think it is a remnant of our evolutionary ancestors. When a person is sitting, pressure is exerted on the coccyx, and it moves forward, acting sort of like a shock absorber. Many important ligaments(e.g. gluteus maximus) attach to the coccyx and play a role in facilitating the bowel and labor movements supporting internal organs and keeping the anus closed. Patients complain when is removed.
Coccyx ? • The coccyx is regarded as vestigial in humans, meaning it no longer serves major functions it did in ancestor species of humans. (Those included supporting a tail and accommodating its nerves.) It does provide an attachment for muscles, such as the gluteus maximus, and also serves as something of a shock absorber when the person sits down, although forceful impact can cause damage and subsequent bodily pains. • http://en.wikipedia.org/wiki/Coccyx
Appendix Small, finger-finger sized structure located at the end of the small caecum, near the beginning of the large intestine. In adults, the appendix averages 10 cm in length but can range from 2-20 cm. Not unique to humans: found in all anthropoid apes, including humans, chimpanzees, gorillas, orangutans, and gibbons, and in several species of New World and Old World monkeys.
Appendix Douglas Theobald claims: The human appendix may have bona fide functions, but this is currently controversial, undemonstrated in humans, and irrelevant as to whether the appendix is a true vestige or not. The appendix is a prime example of dysteleology (i.e. suboptimal structural design), a prediction of genetically gradual evolution. The appendix is a rudimentary tip of the caecum and is useless as a normal, cellulose-digesting caecum. Thus, the appendix is vestigial by both the evolutionary and non-evolutionary, typological definitions of vestigiality. NO! If the appendix does have a function, it is not irrelevant. A function will rule out vestigiality If it does have a function, it must work optimal. Animal organs work optimal. This is an assumption based on evolution Circular reasoning: He first assumes some organs are suboptimal because they are the remnants of evolution, then he finds that the appendix has no function, therefore –he concludes- the appendix is a vestigial organ.
REFERENCES • THEOBALD, D. 2003. The vestigiality of the human vermiform appendix. a modern reappraisal. The Talk.Origins Archive. www.talkorigins.org/faqs/vestiges/appendix.html • ROWLAND, R. 1999. What is the function of the human appendix? Did it once have a purpose that has since been lost? Scientific American.com. • The Harvard Gazette 2014 https://news.harvard.edu/gazette/story/2014/10/status-shift-for-whale-pelvic-bones/