An individual biological neuron can compute a variety of functions, including max and xor, that a single perceptron can't (e.g., https://www.science.org/doi/10.

An individual biological neuron can compute a variety of functions, including max and xor, that a single perceptron can't (e.g., https://www.science.org/doi/10.1126/science.aax6239 https://www.science.org/doi/10.1126/science.aax6239 ). In general, one needs a fairly elaborate ANN to approximate the behavior of a single biological neuron. OTOH, a three-layer network is a universal function approximator and RNNs are universal dynamical systems approximators, so they are sort of trivially equivalent.