Human Gland Probably Evolved From Gills

Why would someone develop a theory which confirms a fraud?

Joel, could you please be clearer? What is a fraud and what confirms it?

I hate to speak for someone else, but I presume he's referring to the mention of Haeckel's pictures, which brings to mind the falsified drawings used to promote his (now discredited) biogenetic law (recapitulation).

While the actual work described above surely does not support the biogenetic law, it's unfortunate that Graham would choose to invoke Haeckel's name. This is probably just a case of a scientist making a historical reference that other scientists will understand (Haeckel is forever linked to embryonic pictures, despite the failure of his hypothesis). However, the statement has now become fodder for creationist quote miners.

Our work has been used in a nationally televised debate to attack evolutionary theory, and to suggest that evolution cannot explain embryology (2). We strongly disagree with this viewpoint. Data from embryology are fully consistent with Darwinian evolution. Haeckel's famous drawings are a Creationist cause célèbre (3). Early versions show young embryos looking virtually identical in different vertebrate species. On a fundamental level, Haeckel was correct: All vertebrates develop a similar body plan (consisting of notochord, body segments, pharyngeal pouches, and so forth). This shared developmental program reflects shared evolutionary history. It also fits with overwhelming recent evidence that development in different animals is controlled by common genetic mechanisms (4). Unfortunately, Haeckel was overzealous. When we compared his drawings with real embryos, we found that he showed many details incorrectly. He did not show significant differences between species, even though his theories allowed for embryonic variation. For example, we found variations in embryonic size, external form, and segment number which he did not show (1). his does not negate Darwinian evolution. On the contrary, the mixture of similarities and differences among vertebrate embryos reflects evolutionary change in developmental mechanisms inherited from a common ancestor (5). [...] These conclusions are supported in part by comparisons of developmental timing in different vertebrates (7). This work indicates a strong correlation between embryonic developmental sequences in humans and other eutherian mammals, but weak correlation between humans and some "lower" vertebrates. Haeckel's inaccuracies damage his credibility, but they do not invalidate the mass of published evidence for Darwinian evolution. Ironically, had Haeckel drawn the embryos accurately, his first two valid points in favor of evolution would have been better demonstrated. (Richardson, 1998) Haeckel, Embryos, and Evolution Richardson, M. K. (1998). "Letter." Science, 280(5366): 983.

Why would someone develop a theory which confirms a fraud?

Abstract It has long been held that the parathyroid glands and parathyroid hormone evolved with the emergence of the tetrapods, reflecting a need for new controls on calcium homeostasis in terrestrial, rather than aquatic, environments. Developmentally, the parathyroid gland is derived from the pharyngeal pouch endoderm, and studies in mice have shown that its formation is under the control of a key regulatory gene, Gcm-2. We have used a phylogenetic analysis of Gcm-2 to probe the evolutionary origins of the parathyroid gland. We show that in chicks, as in mice, Gcm-2 is expressed in the pharyngeal pouches and the forming parathyroid gland. We find that Gcm-2 is present not only in tetrapods but also in teleosts and chondrichthyans, and that in these species, Gcm-2 is expressed within the pharyngeal pouches and internal gill buds that derive from them in zebrafish (Danio rerio), a teleost, and dogfish (Scyliorhinus canicula), a chondrichthyan. We further demonstrate that Gcm-2 is required for the formation of the internal gill buds in zebrafish. We also have identified parathyroid hormone 1/2-encoding genes in fish and show that these genes are expressed by the gills. We further show that the gills express the calcium-sensing receptor, which is used in tetrapods to monitor serum calcium levels. These results indicate that the tetrapod parathyroid gland and the gills of fish are evolutionarily related structures, and that the parathyroid likely came into being as a result of the transformation of the gills during tetrapod evolution.

The links to the quickie embryology recaps are delightful. Last resd that stuff in 1966, but I think I recollect that the parathyroids were known to arise from branchial pouch structures then.

As to ontogeny recapitulating phylogeny, I had the impression that to a certain extent it does, since we are constrained in our morphology by our evolutionary history. Our embryologic divergence from other species reflects our evolutionary divergence.