Living organisms function as protein circuits. We suggest that computational learning theory offers the framework for investigating the question of how such circuits can come into being adaptively from experience without a designer. We formulate Darwinian evolution as a form of learning from examples. The targets of the learning process are the functions of highest fitness. The examples are the experiences. The learning process is constrained so that the feedback from the experiences is Darwinian. We formulate a notion of evolvability that distinguishes function classes that are evolvable with polynomially bounded resources from those that are not. We suggest that the close technical connection this establishes between, on the one hand, learning by individuals, and on the other, biological evolution, has important ramifications for the fundamental nature of cognition.