Human evolution theory utilizing concepts of neoteny & female sexual selection
An etiology of neuropsychological disorders such as autism and dyslexia, and the origin of left handedness.

twitter / andrewL9

Ernst Haeckel

Ernst Haeckel: Excerpts

"Ernst Haeckel, son of a government lawyer, was born in Potsdam in 1834. He took a medical degree in 1858 and, after a short practice, moved to Jena to study zoology under the great anatomist Carl Gegenbaur. He became professor of zoology and comparative anatomy in Jena in 1862 and remained there until his death in 1919. " (Gould, S.J. (1977) Ontegeny and Phylogeny. Cambridge: Belknap Press. p. 76)

"The vitalistic forces of Naturphilosophie could be invoked no longer as the cause of recapitulation. Instead, Haeckel declared his allegiance with physiology in seeking the new path of mechanistic causation: ' a physiological process, which, like all other physiological functions of organisms, is determined with absolute necessity by mechanical causes. These causes are motions of the atoms and molecules that comprise organic material...Phylogenesis is therefore neither the foreordained, purposeful result of an intelligent creator, not the product of any sort of unknown, mystical force of nature, but rather the simple and necessary operation of ....physical-chemical processes. (1866, 2: 365)" (Gould, S.J. (1977) Ontegeny and Phylogeny. Cambridge: Belknap Press. p. 78-9)

"How did Haeckel defend the first premise, that evolutionary change occurs by the successive addition of stages to the end of an unaltered ancestral ontogeny? Since Haeckel is so often cited as Darwin's apostle in Germany, it is generally assumed that he preached a Darwinian interpretation of evlution. In fact, he was only evolution's apostle. Though Haeckel acclaimed Darwin, he ranked Goethe and Lamarck as his equals in the origination of evolutionary theory. (vol 2 of Generelle Morpholoqie is dedicated to them jointly). Haeckel's own view of evolution is a curious and inseparable mixture of all three, each in about the same proportion. To Lamarck, he owed his intense belief in the inheritance of acquired characters. He spoke of this principle as one "auf selcher die ganze Stammes-Entwicklung beruht" (1876, p.47). Though Darwin accepted it as well, he preferred to explain the origin of most variations in other ways. (Vorzimmer, 1970). To Haeckel, however, virtually every useful variation is actively acquired by parents during their life and passed on by heredity to their offspring (natural selection then accumulated and compounds these variations to produce new species). This Lamarckian principle "is an indispensible foundation of the theory of evolution." (1905, p. 863). "The origin of thousands of special arrangements remains perfectly unintelligible without this supposition" (1892, p.211) .... They [Haeckel and most Lamarckians] insisted, rather, that an acquired character would tend to be inherited in proportion to the strength of the force imposing the character upon the organism, the persistence and continuity of that force, and the number of generations upon which the force acted. Now, preadult stages of ontogeny are transient; they do not persist long enough to render transmissible whatever they acquire. But the adult stage, once reached, is permanent; it is therefore subject to the influence of strong and persistent forces that impose upon it (or call forth from it) acquired characters that can be inherited. These acquired characters, the material of evolutionary change, appear as additions to the ancestral adult. "In the course of individual development, inherited characters appear, in general, earlier than adaptive ones, and the earlier a certain character appears in ontogeny, the further back must lie the time when it was acquired by its ancestor" (1866, 2: 298)." (Gould, S.J. (1977) Ontegeny and Phylogeny. Cambridge: Belknap Press. p. 80-81)

"Ernst Haeckel (1834-1919) was arguably one of the most influential biologists of the late 1800s. He was not only a consummate professional, he was also a popularizer: his very clearly written books were translated into twenty or more languages, and sold in hundreds of thousands. Haeckel's most original scientific contribution was to develop to its fullest the idea expressed by Louis Agassiz and Charles Darwin: that embryological developments parallels evolutionary development or that ontogeny recapitulates phylogeny. Here is the way Haeckel expressed his biogenetic law, which he considered to be the fundamental law of organic evolution: 'The History of the Germ in an epitome of the History of the Descent, or, in other words: that Ontegeny is a recapitulation of Phylogeny; or, somewhat more explicitly: that the series of forms through which the Individual Organism passes during its progress from the egg cell to its fully developed state, is a brief, compressed reproduction of the long series of form through which the animal ancesors of that organism (or the ancestral forms of its species) have passed from the earliest periods of so-called organic creation down to the present time." [The Evolution of Man, 1897] (Gottlieb, G (1992) Individual Development & Evolution. Oxford Univ. Press: New York p. 6)

"The laws of homotopic and homochronic inheritance proclaim that an offspring will undergo the ancestral sequence of development in an unaltered spatial arrangement and temporal order. "With these laws, we explain the remarkable fact that the different successive stages of individual development always appear in the same order of succession (Reihenfolge), and the modifications (Umbildungen) of the body always develop in the same parts" (1868, p. 172). Once this is assured, condensation can occur simply by the deletion of certain steps. New adult features can now be added to the shortened ancestral ontogeny: "The chain of inherited characters, which follow each other in a determined sequence during individual development, shortened in the course of time, while certain links of the chain are deleted" (1866, 2: 186). ...Haeckel often states that condensation, or shortened inheritance, is the most important cause of recapitulation." (Gould, S.J. (1977) Ontegeny and Phylogeny. Cambridge: Belknap Press. pp. 83-84)

"Thus, it had to be recognized that evolution involved changes in ontegeny itself, a fact that Haeckel could not accept because of the way he viewed the relationship of ontegeny to phylogeny: the latter was the mechanical cause of the former. As Garstang, de Beer, Goldschmidt, and others were to show in the early twentieth century, it is the mechanically caused changes in ontogeny that bring about evolution and not the other way around as Haeckel believed. This momentous change in the conception of the relationship of ontogeny and phylogeny will be discussed in later chapters. The full conceptual significance of this change in viewpoint--that changes in ontogeny are the basis for evolutionary change--is yet to be realized." (Gottlieb, G (1992) Individual Development & Evolution. Oxford Univ. Press: New York p. 37)

"Among early opponents of recapitulation, Wilhelm His, professor of anatomy at Leipzig, was surely the most effective. He did not acheive this status by marshaling the most telling rebuttals to recapitulation; his specific arguments were, in fact, fairly weak (1874, pp. 165-176). Rather, he challenged Haeckel's methodology and asserted that the most important causes of embryological shapes were proximate and efficient. He sought to explain the complexity of developing form by displaying it as the automatic result of simple mechanical pressures produced by local inequalities of growth. He compared the embryonic layers of the chick to elastic sheets, and tubes, and "constructed" the principal organs by cutting, bending, pinching an folding." (Gould, S.J. (1977) Ontegeny and Phylogeny. Cambridge: Belknap Press. p. 189)

"His's attack had come about ten years too early. In its time it was an isolated incident; but by the late 1880's and early 1890's, two of Haeckel's apostate students -- Wilhelm Roux and Hans Driesch -- were advancing experimental methods in embryology and relegating the biogenetic law to a backshelf of outmoded methods. Before the century's end, T.H. Morgan (1899, p. 195) could write: "If I mistake not, there is a tendency at present, that is slowly gaining ground, to give up an unprofitable the interpretation of ... embryological phenomena in terms of speculative phylogeny." This time, proximate causation triumphed and set the fashion for the next half-century, one of the most exciting and fruitful periods in the history of embryology. Experimental embryologists rejected all aspects of Haeckel's methodology (see p. 187). They were interested in how the structures of juvenile stages worked; they experimented by disturbing the normal course of development; they studied embryonic stages to discover their proximate conditions and to assess their influence upon following ones. In attempting to reduce the complexities of development to laws of physics and chemistry, they focused upon the earliest stages, which recapitulationists usually ignored (patterns of cleavage might yield to mechanical analysis, though the morphogenesis of complex organs seemed intractable). But the greatest clash between the two approaches took place on the battlefield of causality. Experimental embryologists relentlessly asserted that their kind of cause (proximate and efficient) exhausted the legitimate domain of causality. All that had come before them was merely descriptive; they had established the first causal science of embryology. Developmental mechanics {Entwicklungsmechanik} would solve the riddles of ontogeny that had, heretofore, only been recorded n their proper sequence." (Gould, S.J. (1977) Ontegeny and Phylogeny. Cambridge: Belknap Press. p. 194)

"It is satisfying to consider embryos and adults as merely different parts of the slope of a curve subject to natural selection. If biologists cannot agree to Haeckel's concept, "ontogeny recapitulates phylogeny," there may be room for a less ringing slogan, "ontogeny concords with phylogeny."" (Swan, Lawrence W. (1990) The concordance of ontogeny with phylogeny. Bioscience 40: 384)

"Ernst Haeckel went on the argue that the freeing of the hands may have been the prime cause of the great increase in man's intelligence, stimulating our ancestors to explore their environment more thoroughly." (Bowler PJ (1984) Evolution, The HIstory of an Idea. Univ of California Press: Berkeley p. 220)



Related Links