János (John) Szentágothai (JSz), one of the most distinguished neuroanatomist of the
XX. century, has an Erdős number 2, since he has a common paper with Alfred Rényi published in 1956 (actually about the probability of synaptic transmission in Clarke columns). It seems to be a plausible hypothesis that JSz is the bridge to connect the community of mathematicians to neurobiologists and even to philosophers. JSz has a common book with two other scientific nobilities, Nobel prize winner neurophysiologist Sir John Eccles , and with Masao Ito. In this case, JSz should be a bridge between two separated communities. It is interesting to note, that JSz himself was thinking on the graph of the network of the cerebral cortex, in terms of what it is called today “small world”. JSz hinted that the organization of the cortical network should be intermediate random and regular structures. He estimated that “any neuron of the neocortex with any other over chains of not more than five neurons of average.” . Sir John Eccles has a book with Sir Karl Popper The Self and its Brain) so there is a direct math-neurobiology-philosophy chain.
Another non-mathematician with Erdős number 2 via Rényi is András Bródy, a Hungarian economist. They also published a paper in the same memorable year, in 1956. (It was about the problem of regulation of prices.) So, another question is induced. Since most likely all people with number 1 are mathematicians, it would be interesting to know, how many non-mathematicians have Erdős number 2, and how any other scientific communities are involved in the Collaboration Graph?