The most phylogenetically ancient multicellular organisms (that is far enough for our purposes) tend to be composed of relatively undifferentiated sensorimotor cells.1 These cells map certain facts or features of the environment directly onto the motor output of the same cells, in an essentially one-to-one relationship. Stimulus A means response A, and nothing else, while stimulus B means response B. Among more differentiated and complex creatures—the larger and commonly recognizable denizens of the natural world—the sensory and motor functions separate and specialize, such that cells
...more
This highlight has been truncated due to consecutive passage length restrictions.