Human embryos don't have gill slits (Talk.Origins)
- Human embryos do not have gill slits; they have pharyngeal pouches. In fish, these develop into gills, but in reptiles, mammals, and birds, they develop into other structures and are never even rudimentary gills. Calling them gill slits is reading Darwinian theory into the evidence. There is no way gill slits can serve as evidence for evolution.
Source: Wells, Jonathan, 2000. Icons of Evolution: Science or Myth?, Washington DC: Regnery Publishing Inc., pp. 105-107.
This claim is true, human embryos never have gills. What they do have are pharyngeal clefts (Answers in Genesis) that develop into organs that have nothing to do with breathing. Pharyngeal clefts seperate pharyngeal arches which appear as ridges on the outside of the embryo's neck region. The first arch is involved in the development of the face and also ossifies to form the malleus and incus of the middle ear. The second pharyngeal arch ossifies to form the stapes of the middle ear. The fourth and sixth arches give rise to most of the muscles of larynx, pharynx, and soft palate (HEAD AND NECK - PHARYNGEAL (Branchial) ARCHES)
However, Talk.Origins dismisses these pharyngeal clefts as "irrelevant" and continues to assert that they are evidence for evolution because the same structure (pharyngeal arches and clefts) appear in all vertebrate embryos: (Talk.Origins quotes in blue)
The pharyngeal pouches that appear in embryos technically are not gill slits, but that is irrelevant. The reason they are evidence for evolution is that the same structure, whatever you call it, appears in all vertebrate embryos. Agassiz (not a Darwinist himself) said, "The higher Vertebrates, including man himself, breathe through gill-like organs in the early part of their life. These gills disappear and give place to lungs only in a later phase of their existence" (Agassiz 1874). Darwinian evolution predicts, among other things, similar (not identical) structures in related organisms. That pharyngeal pouches in humans are similar to pharyngeal pouches (or whatever you call them) in fish is one piece of evidence that humans and fish share a common ancestor.
The theory being promoted here is the theory of recapitulation (or, in a phrase,"ontogeny recapitulates phylogeny") which claims that "an individual, during its development, passes through a series of stages corresponding to its successive evolutionary ancestors" (Blackwell Publishing). This theory of recapitulation is deduced from Darwin's theory of evolution.
However, recapitulation, as a theory, has been widely rejected as partly or wholely erroneous.
A. C. Seward summed it up well:
It must, therefore, be admitted that one outcome of the progress of embryological and palaeontological research for the last 50 years is negative. The recapitulation theory originated as a deduction from the evolution theory and as a deduction it still remains.(THE INFLUENCE OF DARWIN ON THE STUDY OF ANIMAL EMBRYOLOGY.)
Human embryos have never had gills and the stages the embryo goes through are merely part of the developmental process to form the final product: a human baby. A human is a human starting at conception.