The Problem of Darwinian Correlation

by J. Rogers

Darwin work, The Descent of Man, first published in 1871, is Darwin’s attempt to demonstrate that his evolutionary theory is the logical explanation for the existence of man by drawing connections between species of animals and humans. Early in the work Darwin presents two figures that at first glance seem nearly identical, however one is of a human embryo and the other of a dog embryo.1 Darwin then states that this correlation represents the fact that humans and dogs and all lifeforms come from a common ancestor. This reasoning is wrong.

Thomas Henry Huxley, one of the few people Darwin spoke to about his ideas before having published them, explains the fetal development as so, “[I]t is very long before the body of the young human being can be readily discriminated from that of the young puppy; but, at a tolerably early period, the two become distinguishable by the different form of their adjuncts, the yelk-sac and the allantois. The former, in the Dog, becomes long and spindle-shaped, while in Man it remains spherical; the latter, in the Dog, attains an extremely large size, and the vascular processes which are developed from it and eventually give rise to the formation of the placenta (taking root, as it were, in the parental organism, so as to draw nourishment therefrom, as the root of a tree extracts it from the soil) are arranged in an encircling zone, while in Man, the allantois remains comparatively small, and its vascular rootlets are eventually restricted to one disk-like spot. Hence, while the placenta of the Dog is like a girdle, that of Man has the cake-like form, indicated by the name of the organ.”2 This correlation of form in the early stages of life acted for much of the public as a solid proof that Darwinian evolution was factual, nevertheless, such reasoning overstates the connection.

This overstatement of connection is largely done through cum hoc ergo propter hoc reasoning, or the questionable-cause logical fallacy, sounds reasonable, so much that Darwin used it in his opening chapter. However, correlation does not prove causation; simply because fetal development looks nearly identical between species does not prove that a common ancestor exists. Darwin’s reasoning often falls into this trap, not only in fetal development but also in interspecies resemblances and traits after birth. Darwin also uses this reasoning to explain the common trait of a pentadactyl structure found in vertebrates.3 This is the questionable-cause fallacy at work.

The lack of proof of causation however does not, by itself, disprove the explanation, nor does it prove an opposing view. For example, Answers in Genesis, a Christian organization attempting to disprove evolution states, “Even similarities among somewhat similar creatures reveal that the differences are more important than the similarities. For example, look at the hands of four primates: [tarsier, gibbon, chimpanzee, and human]. Despite the similarities in their hands, the differences are what makes each most suitable for its way of life”4. This is a superficial attempt at disproving evolution, one that Darwin himself dismissed by stating that the changes developed gradually via Darwin’s own theory of evolution.

Both of the proposed arguments as they stand bring us to a dead end, and some believe that by looking at it another way, such as the formation of embryos, a clearer answer can be found. The Japanese zoologists J. Yamane and T. Egashira wrote a study summarized by William E. Castle, found in The American Naturalist, noting the challenges of breeding rabbits and hares. It ends by stating that “it is impossible to get hares to mate naturally with rabbits, and even if this were to occur under exceptional circumstances, no hybrid offspring would result because of the evident inability of the rabbit egg to be fertilized by hare sperm.”5 The complexity of interbreeding leads another dead end. Embryonic formation and development are distinct enough between that species as close as rabbits and hares cannot be combined, and the process only gets more unreasonable when speaking of a class or order rather than genera or species.

Steven Meyer, in Darwin’s Doubt, notes that similar genes can create different characteristic.6 This, it is reasonable to speculate, could lead to similar embryonic forms which develop into specialized forms of body parts.

What does that leave to consider? A lot, and that is the point; the fact that animal life forms from an embryo which, in early stages, may look nearly identical acts as no proof for evolution. Nor can it, by itself, disprove evolution. Whether it is God using the best means to forming life or a piece of evidence to demonstrate Darwin’s theory of a common ancestor, it does not act as proof by itself. As such the larger arguments must be considered with far more weight than embryonic forms.

By J. Rogers

1. Darwin, Charles. “Chapter 1.” Essay. In The Descent of Man, 26–28. Penguin Books, 2004. 
2. Huxley, Thomas Henry. “Man's Place in Nature, and Other Essays by Thomas Henry Huxley.” Project Gutenberg, July 16, 2012. https://www.gutenberg.org/ebooks/40257.
3. Meyer, Stephen C. Essay. In Darwins Doubt, 99–100. Harpercollins Publishers Inc, 2014. 
4. Answers in Genesis. “Similarities Don't Prove Evolution.” Answers in Genesis. Answers In Genesis, July 20, 2015. https://answersingenesis.org/theory-of-evolution/evidence/similarities-dont-prove-evolution/.  [Edited to remove bold lettering]
5. Castle, W. E. “The Hare-Rabbit, a Study in Evolution by Hybridization.” The American Naturalist 59, no. 662 (1925): 280–83. https://doi.org/10.1086/280039. 
6. Meyer, Stephen C. Essay. In Darwins Doubt, 367. Harpercollins Publishers Inc, 2014