Note: This is Part 4 in a series reviewing Jerry Coyne’s Why Evolution Is True. Read Part 1 here, Part 2 here, and Part 3 here.
So evolutionary theory needs better evidence than the fossil record can provide. Coyne correctly notes: “When he wrote The Origin, Darwin considered embryology his strongest evidence for evolution.” Darwin had written that the evidence seemed to show that “the embryos of the most distinct species belonging to the same class are closely similar, but become, when fully developed, widely dissimilar,” a pattern that “reveals community of descent.” Indeed, Darwin thought that early embryos “show us, more or less completely, the condition of the progenitor of the whole group in its adult state.”15
But Darwin was not an embryologist. In The Origin of Species he supported his contention by citing a passage by German embryologist Karl Ernst von Baer:
“The embryos of mammals, birds, lizards and snakes, and probably chelonia [turtles] are in their earliest states exceedingly like one another…. In my possession are two little embryos in spirit, whose names I have omitted to attach, and at present I am quite unable to say to what class they belong. They may be lizards or small birds, or very young mammals, so complete is the similarity in the mode of formation of the head and trunk in these animals.”16
Coyne claims that this is something von Baer “wrote to Darwin,” but Coyne’s history is as unreliable as his paleontology. The passage Darwin cited was from a work written in German by von Baer in 1828; Thomas Henry Huxley translated it into English and published it in 1853. Darwin didn’t even realize at first that it was from von Baer: In the first two editions of The Origin of Species he incorrectly attributed the passage to Louis Agassiz.17
Ironically, von Baer was a strong critic of Darwin’s theory, rejecting the idea that all vertebrates share a common ancestor. According to historian of science Timothy Lenoir, von Baer feared that Darwin and his followers had “already accepted the Darwinian evolutionary hypothesis as true before they set to the task of observing embryos.” The myth that von Baer’s work supported Darwin’s theory was due primarily to another German biologist, Ernst Haeckel.”18
Haeckel maintained not only that all vertebrate embryos evolved from a common ancestor, but also that in their development (“ontogeny”) they replay (“recapitulate”) their evolutionary history (“phylogeny”). He called this The Biogenetic Law: Ontogeny recapitulates phylogeny.
In Why Evolution Is True, Coyne writes that “the ‘recapitulation’ of an evolutionary sequence is seen in the developmental sequence” of various organs. “Each vertebrate undergoes development in a series of stages, and the sequence of those stages happens to follow the evolutionary sequence of its ancestors.” The probable reason for this is that “as one species evolves into another, the descendant inherits the developmental program of its ancestor.” So the descendant tacks changes “onto what is already a robust and basic developmental plan. It is best for things that evolved later to be programmed to develop later in the embryo. This ‘adding new stuff onto old’ principle also explains why the sequence of developmental stages mirrors the evolutionary sequence of organisms. As one group evolves from another, it often adds its developmental program on top of the old one.” Thus “all vertebrates begin development looking like embryonic fish because we all descended from a fishlike ancestor.”19
Nevertheless, Coyne writes, Haeckel’s Biogenetic Law “wasn’t strictly true,” because “embryonic stages don’t look like the adult forms of their ancestors,” as Haeckel (and Darwin) believed, “but like the embryonic forms of their ancestors.” But this reformulation of The Biogenetic Law doesn’t solve the problem. First, fossil embryos are extremely rare,20 so the reformulated law has to rely on embryos of modern organisms that are assumed to resemble ancestral forms. The result is a circular argument: According to Darwin’s theory, fish are our ancestors; human embryos (allegedly) look like fish embryos; therefore, human embryos look like the embryos of our ancestors. Theory first, observation later–just as von Baer had objected.
Second, the idea that later evolutionary stages can simply be tacked onto development is biologically unrealistic. A human is not just a fish embryo with some added features. As British embryologist Walter Garstang pointed out in 1922, “a house is not a cottage with an extra story on the top. A house represents a higher grade in the evolution of a residence, but the whole building is altered–foundations, timbers, and roof–even if the bricks are the same.”21
Third, and most important, vertebrate embryos are not most similar in their earliest stages. In the 1860s, Haeckel made some drawings to show that vertebrate embryos look almost identical in their first stage–but his drawings were faked. Not only had he distorted the embryos by making them appear more similar than they really are, but he had also omitted earlier stages in which the embryos are strikingly different from each other. A human embryo in its earliest stages looks nothing like a fish embryo.
Only after vertebrate embryos have progressed halfway through their development do they reach the stage that Darwin and Haeckel treated as the first. Developmental biologists call this different-similar-different pattern the “developmental hourglass.” Vertebrate embryos do not resemble each other in their earliest stages, but they converge somewhat in appearance midway through development before diverging again. If ontogeny were a recapitulation of phylogeny, such a pattern would be more consistent with separate origins than with common ancestry. Modern Darwinists attempt to salvage their theory by assuming that the common ancestry of vertebrates is obscured because early development can evolve easily, but there is no justification for this assumption other than the theory itself.22
Although Haeckel’s drawings were exposed as fakes by his own contemporaries, biology textbooks used them throughout the twentieth century to convince students that humans share a common ancestor with fish. Then, in 1997, a scientific journal published an article comparing photos of vertebrate embryos to Haeckel’s drawings, which the lead author described as “one of the most famous fakes in biology.” In 2000, Harvard evolutionary biologist Stephen Jay Gould called Haeckel’s drawings “fraudulent” and wrote that biologists should “be both astonished and ashamed by the century of mindless recycling that has led to the persistence of these drawings in a large number, if not a majority, of modern textbooks.”23
But Coyne is not ashamed. He defends Haeckel’s drawings “Haeckel was accused, largely unjustly,” Coyne writes, “of fudging some drawings of early embryos to make them look more similar than they really are. Yet we shouldn’t throw out the baby with the bath water.”24 The “baby” is Darwin’s theory, which Coyne stubbornly defends regardless of the evidence.
Next up, vestigal organs and bad design.
15 Coyne, Why Evolution Is True, p. 79.
Darwin, The Origin of Species, Chapter XIV, pp. 386-396. Available online (2009) here.
16 Darwin, The Origin of Species, Chapter XIV, pp. 387-388. Available online (2009) here.
17 Coyne, Why Evolution Is True, p. 73.
Karl Ernst von Baer, “On the Development of Animals, with Observations and Reflections: The Fifth Scholium,” translated by Thomas Henry Huxley, pp. 186-237 in Arthur Henfrey & Thomas H. Huxley (editors), Scientific Memoirs: Selected from the Transactions of Foreign Academies of Science and from Foreign Journals: Natural History (London, 1853; reprinted 1966 by Johnson Reprint Corporation, New York). The passage quoted by Darwin is on p. 210.
Jane M. Oppenheimer, “An Embryological Enigma in the Origin of Species,” pp. 221-255 in Jane M. Oppenheimer, Essays in the History of Embryology and Biology (Cambridge, MA: The M.I.T. Press, 1967).
18 Timothy Lenoir, The Strategy of Life (Chicago: The University of Chicago Press, 1982), p. 258.
Frederick B. Churchill, “The Rise of Classical Descriptive Embryology,” pp. 1-29 in Scott F. Gilbert (editor), A Conceptual History of Modern Embryology (Baltimore, MD: The Johns Hopkins University Press, 1991), pp. 19-20.
19 Coyne, Why Evolution Is True, pp. 77-79.
20 Simon Conway Morris, “Fossil Embryos,” pp. 703-711 in Claudio D. Stern (editor), Gastrulation: From Cells to Embryos (Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, 2004).
21 Walter Garstang, “The theory of recapitulation: a critical restatement of the biogenetic law,” Journal of the Linnean Society (Zoology), 35 (1922): 81-101.
22 See Chapter Five and accompanying references in Wells, Icons of Evolution.
See Chapter Three and accompanying references in Wells, The Politically Incorrect Guide to Darwinism and Intelligent Design.
23 Michael K. Richardson, J. Hanken, M. L. Gooneratne, C. Pieau, A. Raynaud, L. Selwood & G. M. Wright, “There is no highly conserved embryonic stage in the vertebrates: implications for current theories of evolution and development,” Anatomy & Embryology 196 (1997): 91-106.
Michael K. Richardson, quoted in Elizabeth Pennisi, “Haeckel’s Embryos: Fraud Rediscovered,” Science 277 (1997): 1435.
Stephen Jay Gould, “Abscheulich! Atrocious!” Natural History (March, 2000), pp. 42-49.
“Hoax of Dodos” (2007). Available online (2009) here.
24 Coyne, Why Evolution Is True, p. 78.