" It was Owen who defined 'homologous organs' as 'the same organ in different animals under every variety of form and function'. While he tirelessly demonstrated the multitude of such organs in the animal kingdom, he attributed them to the parsimony of the divine Designer-just as Kepler had attributed his planetary laws to the ingenuity of the divine Mathematician.

But whatever the beliefs of these men, the concept of homology came to stay, and became a cornerstone of modern evolutionary theory. Animals and plants are made out of homologous organelles like the mitochondria, homologous organs like gills and lungs, homologous limbs such as arms and wings. They are the stable holons in the evolutionary flux. The phenomena of homology implied in fact the hierarchic principle in phylogeny as well as in ontogeny. But the point was never made explicit, and the principles of hierarchic order hardly received a cursory glance. This may be why the inherent contradictions of the orthodox theory could pass so long unnoticed. "

― Arthur Koestler , The Ghost in the Machine