The influence of Darwin's theory of natural selection on Cajal's neural doctrine

BARBERIS, SERGIO DANIEL

Simposio; 12th Principia International Symposium; 2021

In this work I intend to elucidate the influence of Darwin's theory of natural selection on the neuron doctrine, as conceived by Santiago Ramón y Cajal. Several historians of science consider that Darwin's influence on Cajal is evidenced in the model of evolution of the structural plan of the nervous system in the animal series that he develops in chapter 1 of the first part of Textura del sistema nervioso... (1899). While it is true that the model in question has evolutionary roots, it is also true that it presupposes two ideas of 19th century biological thought that are not exactly Darwinian. First, Cajal presupposes the idea of Scala Naturae, remarkably persistent in contemporary neuroscience. This first idea is incompatible with the Darwinian idea of evolutionary trees. Second, Cajal presupposes a relatively strong version of the recapitulation thesis. The idea that ontogeny recapitulates phylogeny was criticized and largely transformed in Chapter XIII of the first edition of Darwin's Origin ... (1859). The presence of these ideas in the model of evolution proposed by Cajal in Textura... evidences the reception of Spencer's Principles of Biology (1864) rather than Darwin. I argue that the influence of Darwin's theory of natural selection on Cajal's work is evidenced rather by the laws of economy of space, time, and matter that he introduces to explain the optimal arrangement of cellular elements in nerve centers.