Darwin knew that the Cambrian fossil record was a serious problem for his theory. "It seems to me," Darwin wrote in The Origin of Species, "the leading facts in embryology, which are second to none in importance, are explained on the principle of variations in the many descendants from some one ancient progenitor."
Similarities in early embryos not only demonstrate that they are descended from a common ancestor, but also reveal what that ancestor looked like. Darwin considered this "by far the strongest single class of facts in favor of" his theory. Darwin was not an embryologist, so he relied for his evidence on the work of others. One of those was German biologist Ernst Haeckel (1834-1919). Darwin wrote in The Origin of Species that Professor Haeckel "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."
Haeckel made many drawings, but his most famous were of early vertebrate embryos. Haeckel drew embryos from various classes of vertebrates to show that they are virtually identical in their earliest stages, and become noticeably different only as they develop.
Haeckel made many drawings, but his most famous were of early vertebrate embryos. Haeckel drew embryos from various classes of vertebrates to show that they are virtually identical in their earliest stages, and become noticeably different only as they develop.
Haeckel's embryos seem to provide such powerful evidence for Darwin's theory that some version of them can be found in almost every modern textbook dealing with evolution. Yet biologists have known for over a century that Haeckel faked his drawings; vertebrate embryos never look as similar as he made them out to be. Furthermore, the stage Haeckel labeled the "first" is actually midway through development; the similarities he exaggerated are preceded by striking differences in earlier stages of development. Although you might never know it from reading biology textbooks, Darwin's "strongest single class of facts" is a classic example of how evidence can be twisted to fit a theory.
Haeckel produced many drawings of vertebrate embryos to illustrate his biogenetic law. The drawings show vertebrate embryos that look very much alike at their earliest stage. In fact, the embryos look too much alike. According to historian Jane Oppenheimer, Haeckel's "hand as an artist altered what he saw with what should have been the eye of a more accurate beholder. He was more than once, often justifiably, accused of scientific falsification, by Wilhelm His and many others." In some cases, Haeckel used the same woodcut to print embryos that were supposedly from different classes. In others, he doctored his drawings to make the embryos appear more alike than they really were. Haeckel's contemporaries repeatedly criticized him for these misrepresentations, and charges of fraud abounded in his lifetime.
So why is it still in biology text books? Just one more example of how evolution is forced down our throats with so much evidence showing something else. Don't be misled, find the truth for yourself and remember...
Have an Intelligent Faith!!
- Nelis
Haeckel's drawings aren't considered an evidence for evolution, and his theory isn't being taught as fact. You didn't even describe his theory! It wasn't about the similarity of embryos being evidence for common ancestry in the least!
ReplyDeleteHis theory which HAS been discredited and really isn't being taught as fact was that as the embryo develops it looks at different times like different adult stages of the ancestral history of the organism (that a human embryo would look like a fish embryo, then a reptile embryo, then a mammal embryo, then finally look human)
Thanks for the comment. Many modern biology textbooks inform students that Haeckel's dictum, "ontogeny recapitulates phylogeny," has been discredited, but the same textbooks often use Haeckel's drawings (or modern versions of them) to persuade students that human embryos provide clues to our evolutionary history and evidence for Darwin's theory. Here is an example: in the text book "Molecular Biology of the Cell" it claims that neo-Darwinian mechanisms explain why "embryos of different species so often resemble each other in their early stages and, as they develop, seem sometimes to replay the steps of evolution". And another "The 1999 edition of Raven and Johnson's textbook named Biology" - "Notice that the early embryonic stages of these vertebrates bear a striking resemblance to each other." Elsewhere the book explains: "Some of the strongest anatomical evidence supporting evolution comes from comparisons of how organisms develop. In many cases, the evolutionary history of an organism can be seen to unfold during its development, with the embryo exhibiting characteristics of the embryos of its ancestors".
ReplyDeleteDozens of other biology textbooks published since 1990 have used Haeckel's drawings (or modern versions of them) as evidence for Darwinian evolution. These include textbooks published as recently as 2004. So if it was discredited, why is it still in there?
We are not claiming that Haeckel's embryo drawings and recapitulation theory are the bedrock of evolutionary biology, but if there is ANY doubt about a theory it should be re-examined. If the evidences point elsewhere it should be dismissed completely.
Really hope that this was a satisfactory reply to your comment. If you have any other comments or question, i encourage you to make a video response and we can go from there.
God bless you!