von Bauer’s first law of embryology

According to this law, in the ontogenesis of each species, the individual structures are formed gradually from structures that are common to all the members of the highest taxon to the structures of common members of gradually lower and lower taxa, to which the given species belongs. The historically older von Bauer’s law, which Darwin also mentioned as one of the important documents for the validity of his theory of evolution, is actually substantively more correct that the newer Haeckel’s recapitulation theory. However, there are many exceptions to both the recapitulation theory and von Bauer’s law. In a great many species, the route through which the ontogenesis of a certain structure reaches a certain stage can be modified and some stages can even be omitted in some species (see XII.7.3). It is, however, true that it rarely occurs that the order in which the individual stages appear is reversed and that there would thus be a flagrant breaking of von Bauer’s law and this also the recapitulation theory.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more