7. Teleomechanism and Gill Slits


In 1811 J. F. Meckel - building on the work of Lorenz Oken and others - predicted that gill slits would be found somewhere in the course of development of the human embryo. The theoretical framework that led to this prediction included the idea that all animals can be put in a series of lowest to highest, with the human being at the top. And in addition the development of each 'lower' animal is somehow a partial development of a human being (Oken even described lower animals as 'human abortions'). Thus Meckel reasoned that on its way to becoming an adult human being the human emrbyo must pass through a fish-like stage. In 1825 Heinrich Rathke published on his observations of gill slits in the embryo of a pig, comparing the slits with those of a dogfish. Later in 1825 he also discovered gill slits in a chick embryo. Others immediately followed up this line of research, including von Baer. Both Rathke and von Baer discovered gill slits in the human embryo around 1827.

Prima facie in this case we have a clear example of a temporally novel predictive success. But Meckel's theory seems to include important elements which are not approximately true in any obvious sense. Thus Kyle Stanford (2006, 2009) puts this case forward as a possible counterexample to scientific realism. However, Stanford doesn't investigate whether the *working* posits are approximately true, as the selective realist would claim. Certainly Meckel was *working with* hypotheses which were not approximately true, and this might suggest that the selective realist strategy can't work here. But this would be unfair to the realist: just because a scientist is working with an assumption, that needn't mean that the assumption is truly doing work to bring about the prediction in question.

Thus the jury is out on this case, and work remains to be done to determine whether the selective scientific realist has an answer, or whether it stands as a serious counterexample.


Gould, S. J. [1977]: Ontogeny and Phylogeny, Cambridge, MA: Belknap Press of Harvard University Press.

Meckel, J. F. [1811]: Entwurf einer Darstellung der zwischen dem Embryozustande der höheren Tiere und dem permanenten der niederen stattfindenen Parallele: Beyträge zur vergleichenden Anatomie, Vol. 2, (Carl Heinrich Reclam, Leipzig), pp. 1–60.

Russell, E. S. [1916]: Form and Function, London: J. Murray.

Stanford, P. K. [2006]: Exceeding Our Grasp, Oxford: Oxford University Press.

Stanford, P. K. [2009]: ‘Author’s Response’, in ‘Grasping at Realist Straws’, a review symposium of Stanford (2006), Metascience, 18, pp.379-390.

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