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The Development of the Embryo²⁰

Almost all life is cellular, and each type of organism has a stage in which it exists as a single cell. In the vertebrates the fertilized egg cell develops through a succession of stages to the many-celled adult form. This succession of stages, the process of embryonic development, is sometimes called ontogeny. In the early part of the nineteenth century proposals were made which led German embryologist Ernst Haeckel in 1866 to announce his "fundamental biogenetic law." His idea was that a higher creature in the course of its embryonic development from the single cell stage successively passes through stages similar to the adult forms of the successive evolutionary ancestors which supposedly preceded it during millions of years of evolution from single-celled life to the complex many-celled creature. Since a term for this alleged evolutionary process is "phylogeny," a slogan became popular in some circles: "Ontogeny recapitulates phylogeny." While such an expression may sound erudite and stick in the minds of college students, it does not necessarily correspond to the scientific evidence.

The theory of embryonic recapitulation and the corresponding slogan were widely accepted for many years, in spite of the fact that from the beginning many scientists rejected it because of the large amount of evidence from embryology which contradicts it. The most famous evidence offered in the support of the theory was the presence of the so-called "gill pouches" in the embryos of fish, mammals, and human beings at a certain stage of development. In the fish this structure of blood vessels and supporting membranes becomes perforated to form gill slits by which the fish ultimately breathes in water. The human and other embryos, in contrast, carry out respiration through the placenta and transform the pouches into other organs having no connection with respiration. The idea that the human embryo has "gill slits" is a misrepresentation of facts based upon a presupposition and upon superficial knowledge. These are typical causes of error.

A few of the numerous facts of embryonic development which contradict the theory of embryonic recapitulation are the following: 1. Children develop tongues before teeth, the reverse of evolutionary theory. 2. Vertebrate embryos form the heart before the rest of the circulatory system, the reverse of theory. 3. Some creatures are very similar in the adult stage but quite different in the egg or larval stages, the reverse of theory. 4. Moths, butterflies, and some other insects go through a pupal stage in which all internal structure dissolves into formless jelly, for which there could be no corresponding evolutionary ancestor. 5. In some case the early stages resemble their own adult form more than they do the adult forms of supposed ancestors, contrary to theory. 6. The respiratory surface of the lung is the last to appear in the embryo, whereas it surely would have had to be present throughout the alleged evolutionary history. 7. Some parts of an embryo may have stages which seem to exhibit recapitulation, whereas other parts show no correlation whatsoever with the recapitulation theory.

figure 7-2. Photomicrograph at 40x of chick embryo 43 hours old. Does this embryo portray millions of years of evolutionary history? Or is it developing according to an efficient plan conceived by a wise Bio-Engineer?

Since some similarities to supposed evolutionary ancestors exist in the series of stages in the embryonic development of various animals, we must ask how this fact can fit with biblical creation? The obvious explanation is that each embryo develops its organs through those stages and in the order which meet its needs at each level of its process of development. For instance, since the nervous system is the most complex structure, its formation begins very early in the vertebrate embryos. Therefore, the early stages of vertebrate embryos all have a worm-like appearance because of the prominent bulge of the developing brain attached to the long embryonic spinal cord. Embryonic development points not to unplanned evolution, but to the intelligent programming of a complex building operation.

References

20. Klotz, John W., ibid.(ref. 19), pp. 131-145; Davidheiser, Bolton, ibid.(ref. 19), pp. 235-240.